Saurian

To Chew or not to Chew?

2012-02-09T12:40:00.000Z

In my recent post about Daspletosaurus I made reference, inmy imaginary scenario, that tyrannosaurs were almost certain to swallow theirfood whole once they had torn away the flesh and bone from a carcass.Tyrannosaurs obviously did not chew and so this is a perfectly logicalassumption but hadrosaurs, on the other hand, did indeed utilise a form of chewingwith their unique jaw hinge arrangement and their impressive array of grindingteeth that lined the jaws.

Sauropods, of course, present another conundrum. I mentionedin my previous post that sauropods were almost certainly perpetual eaters andit has always fascinated how so small a head, mounted on a long neck, wascapable of consuming enough food to maintain their giant bodies. Well, like tyrannosaurs,it appears that sauropods also swallowed without chewing and, since so muchfodder would have been required, then this simple action would have been anecessity.

This actually makes a lot of sense since, simply put, largebodies demand large amounts of food and it seems a reasonable assumption that,since sauropods survived until the very end of the Cretaceous, they hadobviously developed a very efficient feeding and digestive system.

Hadrosaurs were also big animals and some, such asShantungosaurus, grew to around fifty feet in length but these animals employeda much more complex chewing and swallowing technique. They were able to processvegetation into much smaller bits of matter; indeed the process of cutting theplants with the horny beak began the process before the dental battery more orless ground the fodder to pulp. This processed mulch was then broken down inthe gut much quicker and easier than if it had been swallowed whole.

To generate the force needed to operate the hadrosaur jawmechanism required significant power and the skull was quite robust and muscledaccordingly. Sauropod skulls, on theother hand, were small and kinetically weak. Sauropods were so big that they did not have the time to utilise such aprocess like that used by the hadrosaurs and this is the primary reason, Isuspect, why hadrosaurs had virtually reached their size limit with animalslike Shantungosaurus.

What sauropods did have, however, was a remarkably long neckand this appears to have enabled the animals to consume vast amounts of fodderin various positions and angles without actually having to move.Physiologically this all makes good sense. If you need to consume copiousamounts of vegetable matter, you are better off with a very simple head thatswallows matter whole, utilising minimal effort with only the neck movingwhilst the body remained virtually motionless. Perfect.

Also of interest is the fact that a lot of Mesozoic floraactually appears to be very nutritious. You may recall during my SVP recap thata recent reappraisal of the Jurassic flora found in the Morrison Formation and a nutritionalanalysis of their equivalent extant varieties reveal that many species of plantwere very nutritious and ideal for the sauropods (Gee 2011). Horsetails wereone of these likely to have been consumed and today’s examples are very tough andfibrous but if you are swallowing your food whole then this does not representa problem (Sander et al 2011). Plants such as horsetails would also have beentough on teeth, and recovered sauropod teeth are often heavily worn, but theywould have been replaced frequently so this would not have been an issue.

Of course, large amounts of fodder require a large stomachfor digestion and the vat of gastric juices, comprising of billions ofbacterial microbes needed to break down such tough fibrous plants, would havebeen very large indeed. It was thought that this may have been supplemented bya stone filled gizzard to help the digestive process, something akin to birdsthat utilise grit in the same way, but, contrary to popular belief, there is nohard evidence to support this theory (Wings & Sander 2007). In any eventthe process of digestion would have taken a long time but this would have notcaused a problem for sauropods since the sheer size of the gut alone would havevirtually ensured a continual release of energy to the animal.

Also of use to sauropods were their unique skeletalpneumaticity and an extremely sophisticated avian-likerespiratory system. The cervical vertebrae were full of air sacs that ran in tandemwith what was obviously a sophisticated series of valves that controlled andregulated both blood flow and air exchange. So not only was the neck lightenedconsiderably, which aided the feeding process, but they were also able to breathemuch more efficiently and this also made the task of supporting their entire bodystructure much easier. In fact this has also just been alluded to in a veryrecently published paper (Sookias 2012).

There are obviously various feeding techniques in dinosaursthat are yet to be fully determined and perhaps oviraptorosaurs, ornithomimidsand therizinosaurs represent those that are amongst the most fascinating andchallenging to describe fully.

References

Gee, C. 2011. Sauropod Herbivory During Late Jurassic Times:New Evidence for Conifer-Dominated Vegetation in the Morrison Formation in theWestern Interior of North America. Journal of Vertebrate Paleontology,SVP Program and Abstracts Book, 2011, pp115.

Sander, P. M.,Christian, A., Clauss, M., Fechner, R., Gee, C. T., Griebeler, E.-M., Gunga,H.-C., Hummel, J., Mallison, H., Perry, S. F., Preuschoft, H., Rauhut, O. W.M., Remes, K., Tütken, T., Wings, O. and Witzel, U. (2011), Biology of thesauropod dinosaurs: the evolution of gigantism. Biological Reviews, 86:117–155. doi: 10.1111/j.1469-185X.2010.00137.x

Sookias, R.B.,Richard J. Butler, and Roger B. J. Benson 2012 Rise of dinosaurs reveals majorbody-size transitions are driven by passive processes of trait evolution ProcR Soc B 2012 : rspb.2011.2441v1-rspb20112441.

Wings, O & P. Martin Sander 2007. Nogastric mill in sauropod dinosaurs: new evidence from analysis of gastrolithmass and function in ostriches Proc Biol Sci. 2007 March 7; 274(1610): 635–640.Published online 2006 December 19. doi: 10.1098/rspb.2006.3763

Dinosaur Conundrums - How did Dinosaurs sleep?

2012-02-02T14:00:00.001Z

One of the best aspects of palaeontology is that no matterwhat we think we know there is always so much that we don’t. Dinosaurpalaeontology is often dominated by cladistics and phylogenetic analysis andthis is quite understandable but, for me, how these animals lived and behavedis much more interesting.

Image © by Jeff Bucchino, "The Wizard of Draws"

How did dinosaurs sleep? Come to think of it, did theyactually sleep at all? The first place to start is with the extant phylogeneticbracket (EPB) which, as most of you are aware, places dinosaurs betweencrocodiles and birds. Crocodiles do sleep, not in the traditional mammaliansense, but in a rather disjointed way by which they tend to grab short sessionsof sleep but without falling into a deep slumber. They sleep with one eye open,so to speak, and are able to be instantly awake at the slightest disturbance.

These short sleeping sessions usually occur after bouts ofactivity and especially after eating although, being poikilothermic, this maynot actually be that often although crocodiles also use these short sessions to shutdown non-essential biological functions to aid digestion. The other thing totake into account with crocodiles is that, if they were to fall into a deepsleep, they would lose control of their body temperature which the animal regulatesby moving in and out of the sun and water to adjust its body temperature. Deep sleep couldbe potentially fatal to any poikilotherm.

We all know that birds sleep as anybody who has kept abudgerigar or parrot will testify. And yet birds too sleep somewhat lightly butfor different reasons. Crocodiles are big apex predators which are able to restcomfortably in the knowledge that it is extremely unlikely that anything willbother them. For birds, the issue of sleep is much more life threatening andfor a bird to be caught off guard and in a deep sleep could be disastrous.

Birds employ a number of strategies when it comes tosleeping which are employed to negate the possibility of being predated when atrest. Some birds sleep on the ground using a combination of camouflage andground cover for protection whilst some water birds will find refuge onpredator free islands or, indeed, sleep on the water itself. By far the mostcommon strategy, which includes birds that spend the majority of their time onthe ground, is to take cover in trees and shrubs. This prevents the vastmajority of ground predators from reaching them and, even if they could climb,chances are that vibration and noise would warn the bird of impending danger.

Safety in numbers is another solid technique for avoidingpredation and some roosts may number hundreds, if not thousands, of birds.Interestingly though, despite all of these anti-predator measures, birds, liketheir crocodilian cousins tend not to sleep very long with an average length oftwo and a half minutes in some phases while other sessions will be counted inthe seconds. Also of note is that birds, particularly those that sleep or perchstanding up, manage to keep their muscles taught when asleep and flexor tendonsensure that the toes lock around the perch thus preventing the bird fromfalling.

So did dinosaurs sleep and, if they did, how? By way ofinference, utilising the EPB, then it is almost a certainty that they did sleepbut just how this occurred must remain a matter of conjecture but we can make afew educated guesses. Theropods ranged in size from very small to very largeand would have employed various resting and sleeping techniques. Since nearlyeveryone agrees that most dinosaurs were much more than ectothermic, and probablynearer endothermic, then it follows that theropods spent a lot of their timeresting or sleeping since hunting and feeding would take up only a smallproportion of their time.

Small theropods may have slept in a squatting position,similar to ground dwelling birds of today, perhaps with the head tucked inagainst the body. Indeed, the high profile discovery Mei long, from EarlyCretaceous sediments in Liaoning Province in China, was found in just such aposition and the name translates as “soundly sleeping dragon”. Although Meirepresents the best evidence of an avian rest posture to date, it is not theonly example and a specimen of Saurornithoides recovered in the early ninetiesfrom Mongolia was found preserved in a similar posture. We must remind ourselves,however, that this is still an untestable assumption of an avian sleep postureand that these animals may have simply died in this position.

Mei long - Image by Bruce McAdam

It is much easier to imagine that small theropods would havebeen able to rest and sleep very comfortably and would have been able to regaintheir footing with some ease. But what do you do if you a big multi-tonnedpredator such as a spinosaur or tyrannosaur? In theory, there is no reason tosuggest that a big theropod could not sleep or rest in the same way that Meimay have done. But it is harder for us to imagine animals approaching 40 feetlong (and more) being tucked up in this position and yet – why not?

Could they sleep standing up? It’s hard to comprehend that abig tyrannosaur weighing a few tons would risk falling over because it fellasleep whilst standing up! But, as we have seen, extant birds do possess themechanisms that prevent just such an accident from occurring so it is notbeyond the realms of possibility that perhaps theropods had similar devicesthat prevented this.

Tyrannosaurus, of course, has been studied intensely sinceit was first discovered and has had its possible resting positions looked attoo. The focus of study centres on the fact that the pubic boot could beutilised to take the weight of the animal as it rested which still left thelegs able to assume multiple positions including kneeling, crouching and, ofcourse, standing. Worth popping over to Dinomorph for afuller explanation.

Whether all large theropods may have utilised the pubic bootis unclear but seems unlikely to me. You would imagine that pubic boots wouldshow signs of stress if being rested on for any amount of time by tons of fleshand bone and yet I am unaware of any study that may have looked into this. Maybewe are complicating things and large theropods were quite capable of lying downto rest and sleep like most extant animals of today. Perhaps it’s time similarstudies were performed on other large theropods, apart from Tyrannosaurus, andcomparisons made.

Of course, if you have four legs, you are much more stableand are less vulnerable to falling down anyway but what happens if you fallasleep. Taking sauropods, by way of example, they obviously needed copiousamounts of food throughout their lives and probably ate almost continually.They are the most likely candidates for sleeping whilst standing up and, again,using birds as the basis here, maybe they had a similar arrangement of tendons that kepteverything rigid whilst they slept although there is not a shred of evidence tosuggest they did. It’s worth pointing out that today’s mammals that sleepupright also possess a similar mechanism but, although this bears norelevance to sauropods or other dinosaurs, is indicative that any creature thatslept upright would almost certainly require counter-measures to prevent afall.

Perhaps, then, sauropods were able to kneel or lay down and this is where the human mind canstruggle to comprehend such actions since an animal approaching a hundred feetlong, weighing upwards of seventy tons, being able to lay down, sleep and getup again almost defies imagination. And yet there is no reason that this shouldbe the case and we have to be constantly aware that Nature is extraordinarilyadept at providing animals with the ways and means to exist – and this wouldinclude both rest and sleep.

Ultimately, understanding how dinosaurs rested and sleptwill always be an inferance based on speculation. It’s worth noting that bothbirds and crocodiles do not spend a lot of their time asleep anyway and it’sentirely possible that dinosaurs only required similar limited amounts of both restand sleep. As usual we are left with more questions than answers, moredichotomies than you shake a fist at and haven’t even thought about howpterosaurs may have slept either!

From Milner et al 2009

References

Milner, ARC, Harris, JD, Lockley, MG, Kirkland, JI, Matthews, NA (2009) Bird-like anatomy, posture, and behaviour revealed by an Early Jurassic theropod dinosaur resting trace. PLoS One 4 (3): e4591. doi:10.1371/journal.pone. 0004591

Lots of free cartoon clipart at the Wizard of Draws.

Prep News

2012-01-26T12:29:00.000Z

A brief post this week and, again, featuring the continuedpreparation of our Oxford Clay plesiosaur. I’ve frequently mentioned the issuesthat have been encountered when comparing specimens from our animal with thosein other institutions and the sometime extreme differences in morphologies ofthe same elements.

We are lucky, in one way, in as much as we have multipleassociated elements from one animal and yet we have struggled to identify thisspecimen, although we have now almost certainly identified this plesiosaur togenus level. But with individual elements, or even parts of larger bones, youcan have much tougher problems with identification. Sure, there are elementswhich can be assigned to, say, a plesiosaur or ichthyosaur but generic identificationis problematic.

But specific isolated elements can also be equallydiagnostic although I have found the identification of some marine reptile bones tobe particularly challenging. For example, plesiosaurs increased the amount ofphalanges in their limbs considerably over what is regarded as the standardplesiomorphic condition. This is known as hyperphalangy and is characteristicof plesiosaur limbs.

Phalanges all look alike and found in isolation are notparticularly helpful although some of the bigger ones are obviously pliosauridin origin. In contrast some other elements can often be identified to genericlevel and cryptoclidid humeri are particularly useful in this respect. It’sinteresting that there are almost certainly odd elements in collections allover the world that not only represent missing elements from known taxa butalso unknown elements from unknown taxa. Again, Spinops comes to mind.

That aside, here are a set of proximal carpals from ourplesiosaur all finished with and prepared. These are, from left to right, the ulnare, intermediumand radiale and are from the same forelimb featured in previous blog posts andI am now working on the distal carpals. After that, there are the first fivemetacarpals to prepare and then this particular forelimb will be finished – theremaining part of the limb has long since vanished. Shortly after I willpublish a brief description and then this particular project will betemporarily shelved because of other projects but eventually the next elementup for preparation is a rather impressive femur and, of course, I will publishposts along the way.

Ventral view

Dorsal view

The Palaeoworld in Miniature

2012-01-19T13:06:00.000Z

Last time, I discussed Daspletosaurus which, by anystandard, was a big theropod dinosaur approaching 30 to 35 feet long – a giantin anyone’s books. Of course, sauropods were much bigger animals and the hugebones of these giants are astonishing to observe in museums all over the world.But there is another world of vertebrate palaeontology seldom seen by thepublic, a world hidden from view but one that is absolutely fascinating in itsown right – and at the other end of the spectrum from the world of the giants.

The collection andstudy of microvertebrate fossils is one of those disciplines that are currentlyright at the cutting edge of palaeontology – and with good reason. It revealsso much about the flora and fauna in different ecosystems that would otherwise beignored and lost if all we concentrated on was macrovertebrate collecting.

This increased knowledge of diversity in any givenpalaeoenvironment also enables a more accurate estimation of climaticconditions and increases the taphonomic value of the sites. And now, because ofthe increase in the amount of time and effort being put into the study of thesemicrosites, more new species are being identified every year. The most highprofile example of this in recent years was Steve Sweetman’s work on the Isleof Wight which received international exposure in 2009 as he had apparently identifiedover 50 new species including dinosaur, mammal, bird, pterosaur, crocodile andmany other taxa.

But what exactly is a microvertebrate fossil? In simpleterms they are typically exactly the same fossils that you might find in anymacrovertebrate bearing strata – except that you very rarely see them or,indeed, they are invisible to the naked eye. The best way to collect this typeof fossil is to remove large quantities of sediment from the exposedfossiliferous beds in preparation for screen washing.

However, this is not as simple as shovelling lots ofsediment into buckets and thinking it’s a job well done. On the contrary, aswith any quarry, the relevant taphonomic and stratigraphic detail need to betaken into account and the site itself must be quantified before collectingsince each site is likely to be different and collection methods will vary.

Screen washing, or wet sieving, has been utilised since atleast 1847 by Theodore Plieninger in continental Europe and then by CharlesMoore in the UK during 1858, who sorted sedimentary matrix removed fromRhaeto-Liassic beds near Holwell, Somerset. The first record of screen washingin North America is by J.L. Wortman in 1891 for the American Museum of NaturalHistory and later followed by Barnum Brown, also of the AMNH, who, in 1906, wetsieved sediments from the Hell Creek Formation in Montana. Brown commented that“This material gives evidence of a much greater Laramie fauna than has beenheretofore described” (McKenna et al 1994).

Screen washing is a relatively simple process. Initially,water is passed through the sediment via a couple of screens of different meshsizes. The first mesh is always of a coarser grade and this traps larger debrisas well larger bone and plant fossils. The second mesh is of a much finer gradeand sorts out the much smaller matrix and microfossils - and there are evenfiner meshes if so required.

Nowadays a lot of this matrix is then processed utilisingheavy liquid separation which uses chemicals to separate fossil material from thedebris due to fact that the specific gravity of fossil bone is heavier than thesurrounding particles it is buried with. Using the correct chemical with aspecific gravity less than the fossil material would mean that the fossilswould sink in the solution and can be removed whilst the unwanted sedimentwould float. This is a very simplified description of a somewhat complex processwhich, just as with any other part of preparation, has to take a multitude offactors into account before separation can begin.

This prepared concentrated matrix can then be sorted outwhich is intensive, time consuming and, at the same time, compulsive andbeguiling. Of course, different grades of concentrated matrix will require adifferent approach. The coarser grades can be sifted through comfortably withno other aids other than, perhaps, a simple hand lens but when it comes to fineand ultra-fine concentrate then a binocular microscope or, getting more commonthese days, a good quality USB microscope is essential.

A couple of my colleagues and I have been getting to gripswith these microscopes and they take a bit of getting use to mainly because ofthe slight time delay between actually moving material and seeing it translate ontothe screen. This comes with practice as does knowing your left from your rightwhich, although is plainly obvious on aday-to-day basis, can be a nuisance depending on how the scope is set up as amovement left may actually register as a movement right on the screen.

The matrix is best spread thinly and not in a little pilesince this makes it difficult to discern which particles have been looked atbefore, then after, thus avoiding wasting time by looking at them again. Whenyou first begin sorting you tend to check every granule because sometimes theylook like they may be a fossil and you want to be sure but you soon realisethey are not and the vast majority of fossils are clearly what they appear tobe and are seldom difficult to recognise. Indeed, so many of them are exactcopies of their larger brethren that there is no doubt as to their animalorigins.

When you find a fossil it is nigh on impossible to pick themup with tweezers since you may damage them or they ping out never to be foundagain *cough*. Far better to use a piece of tape to gently secure it and thencarefully ease it into a holding receptacle – masking tape is best since thisis not very sticky at all and fits the bill nicely. McKenna et al (1994) recommenda wet brush to do the same job.

I guess this appears a lot of trouble on the face of it butthis is extremely important work to aid our understanding of thepalaeoenvironment, as an indication of temporal constraint and dating rockunits, and just how diverse life was throughout prehistory. For me, I alwaysamazed at how something so small and barely visible can be so perfectlypreserved after millions of years have passed.

A superbly preserved jaw recently sorted from some Maastrichtian concentrate

Reference

McKenna, M.C., Bleefield, A.R. & Mellett, J.S. 1994.Microvertebrate collecting: Large-scale wet sieving for fossil microvertebratesin the field; pp. 93 – 111 in P. Leiggi and P. May (eds), VertebratePaleontological Techniques, volume 1. Cambridge University Press, Cambridge,UK.

Daspletosaurus is the Key

2012-01-12T13:22:00.000Z

Southern Alberta, 77 million years ago and beside a largetract of marshland, feeding on the carcass of an adult Brachylophosaurus, arethree adult daspletosaurs. All three tyrannosaurs consume everything they canrip away from the carcass with their powerful jaws and great swathes of meat,tendon and bone are swallowed whole – nothing is disregarded.

There are frequent disputes over dominance of the carcassand although the snarling displays of aggression rarely amount to much, theydo, on occasion, snap at each other’s head and bite down hard. These clashesare only brief – instinct tells the tyrannosaur that this form of interactioncan cause severe damage and infection if prolonged.

Suddenly, all three tyrannosaurs become aware that they arenot alone and each one, in turn, notices movement in the undergrowth and in thesurrounding treeline. This merely stimulates them to eat faster and now copiousamounts of hadrosaur disappear down their gullets with hardly any thought. Allthat matters is to eat as much as you can as fast as you can.

A troodontid, almost casually, steps into view but althoughthe daspletosaurs are already aware of him, they give him short shrift and carry on feeding – they know theystill have some minutes remaining. Eventually other troodontids appear and thenanother, then another until there several of them surrounding the feedingcarnivores. A sudden movement behind them causes one of the tyrannosaurs tolook behind him and he sees other predators approaching – this time they aredromaeosaurs. He knows it is nearly time.

The troodontids slowly approach the carcass and, as they do,the daspletosaurs raise their heads, snap their jaws and issue a very deep lowfrequency growl from within. The intruders both front and rear stop and take astep back but it does not put them off for long and this game is played outagain and again over the coming minutes and still the daspletosaurs continue tofeed as much as possible.

Eventually the intruders almost reach the carcass and thenone of them takes a quick bite out of the carcass. This time one of thedaspletosaurs quickly reacts and issues a large roar and takes a step forwardtoward the impudent troodontid. Again this temporarily halts the advance butnot for long. Soon other troodontids, as well as the dromaeosaurs, beginnipping at the remnants of the hadrosaur and now, as their stomachs becomefull, the tyrannosaurs eventually begin to give way and allow the smallerpredators to keep darting in and out, taking scraps of flesh.

All of a sudden the harassment becomes too much for onedaspletosaur and he tears off a huge haunch of hadrosaur and carries it awayinto some trees. The remaining two daspletosaurs continue to feed but, in theend, they too break away from the feast and move off leaving what is left ofthe carcass for their tormentors and the carcass almost disappears from sightas the seething mass of small predators’ attack what’s left with abandon.

The daspletosaurs go their own ways for this was not astructured, coordinated kill – rather it was mutually advantageous to bring thehadrosaur down as a threesome as opposed to an individual attacking on theirown. Each will return several times to the spot of the kill in the days aheadto see if anything remains and what can be scavenged. If they meet up with eachother again, they will give their opposites a wide berth since they do notusually interact unless it is time to mate or if the opportunity to join a killarises again.

The skull of Daspletosaurus
Image by AStrangerintheAlps

Of course, all the above is purely conjecture on my part butthere is some palaeontology in there as well. The age, terrain and fauna areall correct as are some other details such as face biting and the crushing andswallowing of bone. But it is really my way of discussing what I consider tobe, not only the most fascinating, but also looks like turning out to be probablyone of the most important tyrannosaurids in the next few years –Daspletosaurus.

Daspletosaurus torosus was named in 1970 by Dale Russell.The holotype CMN 8506 essentially consisted of the skull and skeleton but therewere no hind limbs recovered save for one femur. The specimen was recovered byCharles Sternberg in 1921 from the Late Cretaceous Oldman Formation in Alberta,Canada. When first collected, Sternberg initially thought the skeleton representedGorgosaurus or indeed, as it turned out, to be a new species.

Daspletosaurus has a number of things going for it whichmake it such an intriguing object of study. Firstly, it is a tyrannosaurine andis closely related to Tyrannosaurus although its actual systematic relationshipwithin tyrannosaurinae remains unclear for now. Secondly, there are multiple species ofDaspletosaurus with the majority of these still to be diagnosed, formallydescribed and named. Just what this will mean for tyrannosaurine systematicsand synonymy is unclear.

Another fascinating issue is the fact that, in the DinosaurPark Formation in Alberta, Daspletosaurus sp. actually co-existed withGorgosaurus which has been taken as suggestive of niche partitioning betweenlarge theropods, since Daspletosaurus is a much more robust animal than thelightly built Gorgosaurus. This was considered a somewhat unusual occurrence atfirst but now more formations around the world are demonstrating similar co-occurrencesof large theropods co-existing and this further blurs the issue.

There is even a little legend surrounding Daspletosaurus andthat is that, not only did it have proportionately the biggest forelimbs of anytyrannosaurid, but it also had the biggest teeth, proportionately, of anytyrannosaur – including T.rex. But I have never been able to find a referencefor the statement about the teeth and if you are aware of the origin of this“fact” then I would very grateful if you would let me know.

Daspletosaurs are also known from bone beds and a site inthe Two Medicine Formation in Teton County, Montana has revealed the remains ofover three individuals, including a juvenile, and may be suggestive ofgregarious tyrannosaurs similar to the albertosaurs of the Dry Island bone bed.This is still a matter of conjecture, however, and the Teton County site alsocontains multiple remains of hadrosaurs.

Daspletosaurus, as a species, is undoubtedly of crucialimportance in our understanding of faunal endemism and isolation in LateCretaceous North America, the origins and dispersal of tyrannosaurines and ouroverall understanding of tyrannosaurid systematics. Essentially, Daspletosaursare very cool animals and are, for me, the quintessential tyrannosaurid – they areuber-cool.

Incidentally, Anthony Maltese, over at the Rocky MountainDinosaur Resource Center (RMDRC), has published a number of times on his blogabout preparation of two daspletosaurs known as Sir William and Pete 3. SirWilliam has finished being prepped now but Pete 3 is undergoing preparation right nowand, with the main jacket still to come, I would expect more posts in the future aboutthe project. A lot of the material is truly awful and they are performingmiracles in restoring this important specimen. Head over there now and take alook if you have not already done so.

Daspletosaurus in the Field Museum
Image by brianbrarian

Reference

Russell, D.A. 1970. Tyrannosaurs from the Late Cretaceous of Western Canada. National Museum of Natural Sciences Publications in Palaeontology 1:1-30.

Comprehending Time & Morphology

2012-01-05T13:03:00.003Z

As we enter 2012, it is always fascinating to realise thatour comprehension of time, on a planetary scale, is somewhat vacuous. We liveour lives by the calendar and by the clock as the year becomes months, weeks,hours, minutes and seconds – we can even split seconds into thousandths andbeyond if we wanted to. But our very existence on this planet is as fleeting assmoke in the wind.

As palaeontologists, we are used to dealing with a muchlarger time scale – mostly the years quoted are in the million, only daring todrop into the mere hundreds of thousands of years when radiometric datingestablishes a timeline, for example, of 75.3 million years. And yet despite ourunderstanding of the vastness of past time we all truly struggle to comprehendit and little wonder.

This often crosses my mind and is sometimes brought homewhen you least expect it. In the vaults of museums around the world there aremany plaster jackets securing what must be hundreds of tons of fossil bonescollected over the years. For example, during my recent visit to the NaturalHistory Museum (NHM) in London, I was able to observe sauropod materialundergoing preparation for the first time since it was collected back in theeighties. Around thirty years have passed until the material was selected forpreparation.

Thirty years, by today’s standards, is a long time in themodern world but would not register in the geologic sense. Indeed, the newcentrosaurine Spinops was originally excavated in 1916 by the Sternbergs onbehalf of the NHM but was only begun to be prepared in 2008 – a gap of 92years. I’ve seen older though and witnessed hadrosaur casts dated 1912, alsofrom Alberta, under preparation a couple of years back but the oldest specimenthat was (and still is) undergoing preparation is the holotype of Hylaeosaurusarmatus. Named by Mantell in 1833, the bones are encased in an unforgiving hardmatrix that only yields after substantial man hours and all this 179 yearsafter the animal was named.

179 years! It seems astonishing that such an importantspecimen is still being prepared but, of course, there are always other considerationssuch as money, priorities, resources and even a couple of world wars that getin the way of such things. But 179 years is still as nothing compared to worldof the Early Cretaceous of around 135 million years ago when Hylaeosaurus wasalive.

But is the fact that these bones, and the jackets they are encasedin, are left unprepared for many years actually of any consequence? Probablynot. They were lying undiscovered for millions of years before being removedfrom their stony graves anyway and whether they are prepared now or in afurther 200 years’ time makes no difference time wise – unless, of course,there is a pyritisation problem but even this is being addressed now and methodsare being developed that can stabilise this form of decay to a degree.

One specimen that is being prepared is our plesiosaur fromthe Oxford Clay and here are the latest bones to be prepared and represent anarticulating ulna and radius. There is a clear foramen between the two whichhas manoeuvred us into yet another area of investigation and may lead tosomething that is going to, perhaps, make me eat my words!

We took some of our “diagnostic” plesiosaur material to theNHM just before Christmas and were very fortunate to be granted access to someof the cabinets that holds the Leeds Collection – a huge amount of marinereptile material that had been amassed from the Oxford Clay many years ago. Weexamined specimens of both Cryptoclidus and Muraenosaurus, including thespecimens described by Andrews (1910) in his Catalogue of Marine Reptiles ofthe Oxford Clay.

A few things of note. Some of these plesiosaurs are hugeanimals and some examples of the forelimbs are well over a metre in length. Thehumeri are massive and clearly dictate that our specimen is very much ajuvenile. The other thing of note, and so striking, is that a great many of thebones are crushed and/or distorted whilst our animal is not and, as a result,even more interesting. The radii, ulnae and carpals in the vast majority ofspecimens we examined were crushed and direct comparison always had to betempered with a degree of caution because of the amount of pressure inducedvariance on the bones.

So what did we find out? The humeri of the specimens weexamined were all well preserved with only a little distortion and yet therewas not one example that we could say for sure was a match. The proximal end,in particular, is problematic in our example and there was nothing like it thatwe could find. The other compared elements fared little better as we might findone bone extremely similar and yet all the others would be considerably different- and so it went on.

There were multiple examples examined, including bothjuveniles and adults, but in the end it was obvious there would be nodefinitive answer for us that day. If I now had to guess an identity from theknown taxa in the clay I would, believe it or not, err on the side of it beinga juvenile Muraenosaurus and, if Chris Traxon is reading this, then well doneyou since you pointed that out to me some months ago. I said at the same timethat I thought Muraenosaurus to be a much more robust animal than this specimenbut I have also underestimated the astonishing amount of changes in bonemorphology throughout ontogeny.

However, there are still too many variables in the overallmorphology of the bones that still suggest it is something different and westill have to check out Cryptoclidus richardsoni which is, without a doubt, themost similar example we’ve seen – especially the specimen (GLAHM V1809) at the Hunterian. Itis apparent that further comparison will be required and if we are stilldissatisfied with the outcome then the specimen will go to London at some pointfor further study.

Incidentally, the Leeds collection is absolutely astonishingand we were granted access to only part of it and it is truly a wonderfulcontribution to our understanding of the Callovian Sea and is, of course, ofinternational importance. It would benice to see the collection displayed one day, perhaps in a special exhibition –it is truly a unique collection.

Reference

Andrews, C. W. 1910. A descriptive catalogue of the marine reptilesof the Oxford Clay, based on the Leeds Collection in the British Museum(Natural History), London, Part I. British Museum (Natural History), London.

2011 Reviewed

2011-12-30T18:39:00.000Z

2010 was an astonishingly busy year in the world ofpalaeontology and was often referred to as the year of the ceratopsians. 2011has also been an amazing year and, looking back, it’s hard to think ofdeclaring it as the year of anything in particular but, if I had to, I woulddeclare 2011 the year of that most iconic of animals, Archaeopteryx. Here aresome things that caught my eyes and ears during this most fascinating of years.

In January we were treated to the announcement ofTeratophoneus curriei, yet another tyrannosaurid from the Carr and Williamsonstable, presented as the most basal tyrannosaurine known from North America.“Currie’s monster murderer” provides further evidence of regional endemism inthe American southwest.

Also, in January, there was another suggestion thatdinosaurs may have survived the KT impact by as much as 700,000 years after agroup of scientists, led by Larry Heaman of the University of Alberta, dated a hadrosaurfemur using U-Pb (uranium lead) dating technology to 64.8 million years old.The researchers believe that if more recovered material is dated accordinglythen the extinction date of the dinosaurs will almost certainly have to berevised.

February was fairly quiet although it was good to see MikeTaylor featuring in the New York Times, who briefly looked at his career in thewake of the announcement of Brontomerus mcintoshi. March, however, saw Greg Paulstir up the proverbial hornet’s nest by suggesting, albeit in a roundabout way,that his style of artistic restoration i.e. the “Greg Paul Look” is more orless his own copyrighted style and that permission should be sort before “hisstyle” is utilised by other artists. He also appeared to criticise otherartists for daring to sell images, in “his style”, at prices less than otherwell established artists would charge!

I am a huge admirer of Greg Paul, both as a palaeontologistand artist, but this did seem to be a little disingenuous and rightly provokeda huge response and outcry in the palaeoworld and the arguments that followedproved both fascinating and enduring. Just where this will end up in the futureis anyone’s guess.

March also saw the announcement that a motion picture ofWalking with Dinosaurs in 3D would be hitting the cinemas in 2013. With abudget in the region of 65 million dollars the film promises to use groundbreaking 3D and LIDAR technology to make it the ultimate dinosaurian encounter.Of course, whether we can expect some science in the film is anyone’s guess butwe all remain ever hopeful.

Another tyrannosaur made the news in March – this one beingZhuchengtyrannus magnus, brought to us by Dave Hone et al. Identified from anassociated maxilla and dentary, Zhuchengtyrannus is yet another interestingtyrannosaurine and comparable in size to both Tarbosaurus and Tyrannosaurus.

April was a personal triumph for me as I found my firstpartially articulated plesiosaur in the Oxford Clay. The animal appears to be ajuvenile and remains unidentified but it is slowly being prepared and thisprovides yet more detail as we proceed. We may be little closer to identifyingthe animal now after we compared some elements with multiple examples ofplesiosaurs in the Leeds collection at the Natural History Museum in Londonlast week – but a degree of certaintyremains elusive.

Back to tyrannosaurs and a superb paper describing the skullof a juvenile Tarbosaurus was published in May in the Journal of VertebratePalaeontology by Tsuihiji et al. I said at the time that I thought this was thepaper of the year for me and I still do. The description of the cranialosteology of the specimen is an excellent and lucid account and the paper isset out spot on in my humble opinion. Read it now if you have not already doneso.

Premiering in June, Dino Gangs was a documentary on theDiscovery Channel featuring Phil Currie’s assertion that the tyrannosaurine,Tarbosaurus, hunted in packs. This was reviewed at multiple sites and blogsand met with a mixed reaction which, in the end, probably came out on thepositive side of things. I felt that it was, overall, a good programme but thatthe assertion that tyrannosaurs hunted something akin to mammalian pack huntersof today was a little fanciful but at least the opposite view was fairlyrepresented, albeit only briefly.

2011 was the 150^th anniversary of the discoveryof Archaeopteryx and the celebrations were launched, in earnest, during June.The Museum fürNaturkunde in Berlin launched a special exhibition which not only displayed theBerlin specimen in all its glory, but also the counter slab for the firsttime, and also the original fossil feather that was first designated asArchaeopteryx.

The monograph describing Scipionyx samniticus was published towhat appeared to be universal acclaim by the palaeoworld and huge praise waslavished upon the authors, Cristiano Dal Sasso and Simone Maganuco. It isunusual for such a monograph to be so well received and the authors are to becongratulated for producing such a fine (and important) publication andcontribution.

July saw the news that Jurassic Park 4 was definitely going to bemade – again. Steven Spielberg made the announcement in San Diego at Comic-Con2011 and met with, yet again, a mixed reaction from fans and the palaeoworldalike. I suggest we wait until the film actually goes into production beforeanything else since there are no guarantees that it will ever get made in thefirst place.

Also during July was the assertion that Archaeopteryx was morelikely to be a basal dromaeosaur as opposed to being a basal bird. A new paperby Xu et al describe a new theropod from China that suggests that featuresfound in Archaeopteryx, thought to be diagnostic of Avialae, are actuallycharacteristic of Paraves. As you canimagine, this invoked huge discussion in the palaeoworld and was to take yetanother direction later in the year.

In August it was announced that scientists had successfullycreated chicken embryos that grew crocodile-like snouts instead of beaks. Byadjusting their DNA to resemble alligator genes, the beak development was haltedand snouts developed instead. Genetic signalling such as this is becomingbetter understood with every passing year and Jack Horner’s “Chickenosaurus” isalmost certainly just around the corner, if it has not already been done.

The suggestion that plesiosaurs may have given live birth isnothing new but evidence provided by F.R. O’Keefe and Luis Chiappe in Augustcertainly was. Mentioned a couple of times in this blog, a specimen ofPolycotylus latippinus clearly displays an embryo within the body cavity of theadult and suggests that these plesiosaurs may have given birth to a single welldeveloped newborn that was possibly dependent on the adult for care.

September was a bumper month for dinosaur television with DinosaurRevolution, Planet Dinosaur and Terra Nova all premiering. Both DinosaurRevolution and Planet Dinosaur were generally well received by the palaeoworldwith both having strengths and weaknesses although, having seen both series, Ifeel that Planet Dinosaur was the more superior product from the scientificview point. They were both, however, a significant improvement on previousattempts at portraying the prehistoric world. After a slow start, Terra Novaslowly improved and it seems likely that a second series will now go aheadalthough we will probably have to wait until May for confirmation of that.

Also in September, Nick Longrich et al presented evidence thatdemonstrated that Late Maastrichtian birds were flourishing and diversifyingright up to the moment that the K-T extinction occurred. The team identified 17species that all failed to survive into the Paleogene and included birds ofvarious sizes across a range of groups. This is the first evidence thatcontradicts the suggestion that archaic birds were gradually becoming extinctthroughout the Late Cretaceous and then disappeared at the same time as theChicxulub asteroid strike.

Other items of interest in September include the first possiblepreservation of dinosaurian feathers preserved in 79 million year old amberfrom southern Alberta in Canada. Some of the preservation is outstanding anddisplays exquisite filaments and, amazingly, remains of pigment which has allsorts of implications as the search to reveal the colours of dinosaurs hots up. A new troodontid was also announced inSeptember, Talos sampsoni, and is the first troodontid to be named in NorthAmerica for the best part of 75 years and the Hadrosaur Symposium took place atthe Royal Tyrrell Museum in Alberta to much acclaim and there was somesignificant work presented regarding these wonderful animals. The volume ofpapers that will follow is sure to be in great demand and will greatly add toour knowledge of these fascinating creatures.

In October, a paper presented at the annual meeting of theGeological Society of America, lowered the bar for a so-called scientific paperby suggesting that not only did a giant kraken-sized squid prey on giantichthyosaurs (for which there is no evidence) but also rearranged their bonesin nice patterns to form a self-portrait! No need to say anymore about thisreally except that it has been universally condemned by all in the palaeoworldbut it is unfortunate that it managed to get so much air time and press.

New images of a stunningly preserved theropod hit the wires inOctober and caused quite a stir. What a magnificent specimen it is and is 98%complete. Unusually, the paper and name of this animal are still to be releasedand, hopefully, Oliver Rauhut and his team won’t keep us in suspense for toomuch longer.

Earlier I mentioned how Archaeopteryx was now possibly a basaldromaeosaur but in October he was back to being a bird again as Michael Lee ofthe South Australian Museum performed a much more rigorous phylogenetic analysisusing a superior and sophisticated statistical methodology. This draggedArchaeopteryx back from dromaeosaurs and nestled the animal quite happily backamongst the birds and highlights the fine line between what is a bird and whatis a dinosaur – although, of course, they are one and the same thing. Stillwith Archaeopteryx and the London specimen (BMNH 37001) was finally designated theneotype by the ICZN since the original holotype was a feather and could not bedesignated to Archaeopteryx alone since there were almost certainly otherfeathered animals that shared the sameenvironment.

In November, it was suggested that the plumage of Archaeopteryxwas likely to be black in colour after Ryan Carney and his co-authorsdiscovered that the melanosomes identified on an Archaeopteryx feather weremost likely to be black. These were identified using scanning electronmicroscopy and then comparing them with similar feathers from 87 extant birdspecies.

The Society of Vertebrate Paleontology annual meeting took placein Las Vegas and was one of the biggest meetings ever held. There were amultitude of presentations and posters that have been covered extensively onthis blog and I covered only a fraction of the data that was presented.Finally, in November, tyrannosaur aficionados were interested by tyrannosaurremains reported from the Turonian of Uzbekistan. Authors Alexander Averianovand Hans-Dieter Sues suggest that the remains represent a non-tyrannosauridtyrannosauroid more basal than the Campanian tyrannosaurids Bistahieversor andAppalachiosaurus.

There was still no let up in December as the new ceratopsianSpinops sternbergorum was announced, Alamosaurus was designated as the biggestNorth American sauropod – comparable to Argentinosaurus in size, andNedoceratops became the latest casualty in the continuing synonymising ofchasmosaurines, turning out to be an ontogenetic stage between Triceratops andthe “Torosaurus” morphology. The mind boggles.....

This time last year, like the previous year, I was wondering if2011 could possibly live up to the previous year but it has. As we go into 2012I find myself wondering the same and yet the world of palaeontology has becomea fast moving breathing object that has spread out across the globe and encompassesso many wonderful people who share the passion – some I am lucky to call bothfriend and colleague. I have no doubt that 2012 will be another fascinatingyear for all of us. Happy new year to you all.

Crocs at Christmas

2011-12-23T10:06:00.001Z

It occurred to me the other day that despite my extensivecoverage of the Oxford Clay Formation and the abundant vertebrate fauna thatinhabited these warm shallow tropical seas, I have actually not devoted anyreasonable coverage to the marine crocodiles that shared the environment withthe better known ichthyosaurs, plesiosaurs and pliosaurs.

There are currently two genera represented in the clay andthese are Steneosaurus (the superb specimen above is from Holzmaden) and Metriorhynchus. These are both thalattosuchians thatshare their ancestry with the crocodiles and alligators of today and so belongto an ancient and very successful group whose origins can be traced back to theLatest Triassic – around 200 million years ago.

The early crocodiles were small and essentially land livinganimals. Eventually they evolved into water dwelling genera, the mesosuchians,which spread rapidly and became very successful, filling a variety of niches.These mesosuchians eventually gave way to more derived forms and some of thesereturned to the land while others went to sea.

Steneosaurus is a very familiar looking animal and couldeasily be mistaken for a gavial of today and it seems likely that it would haveshared a very similar mode of life to its extant cousin. Approaching 4 metresin length, Steneosaurus was well adapted to a marine life. The skull waslightly constructed and the rostrum was elongate, narrow and there were over 40teeth in both the upper and lower jaws. These teeth were conical, sharp andwere ideal for catching fish and invertebrates that shared the environmentalthough some specimens also display blunter teeth that may have been suited todealing with more robust prey.

The limbs of Steneosaurus were typically crocodilian, as wasthe upper torso of the animal, which was covered with a layer of ornateprotective osteoderms. The tail, again,was extremely crocodilian, being long and powerful, and was clearly asignificant propulsion unit for swimming.

Two species of Steneosaurus are generally accepted to havebeen part of the Oxford Clay fauna and these are S. leedsi and S.durobrivensis. The fact that their fossils are found in these marine sedimentstends to confirm a gavial-like existence and Steneosaurus probably inhabitedthe coastal shores and the mouths of rivers that emptied into the sea.

The other crocodile that is found in the Oxford Clay is Metriorhynchusand this genus is much more robust than Steneosaurus, although not as long, andis fully adapted for life in the sea. About 2 to 3 metres in length, the limbs of Metriorhynchus were fullydeveloped flippers and were unsuitable for life on land. Of course, it wouldseem logical to assume that Metriorhynchus would have returned to shore to layeggs but now, with evidence that plesiosaurs gave birth to live young, perhaps weshould not so readily make such an assumption.

The tail is a little similar to an ichthyosaur tail in asmuch as the caudals bend downward to create a proper fish-like tail and thisanimal was obviously a very efficient swimmer. Metriorhynchus completely lacksthe dermal ossifications of Steneosaurus and this is always the best identifierwhen a crocodile skeleton is first revealed in the clay. The skull is stilltypically long but the rostrum is much broader than in Steneosaurus, and looksmore crocodilian than gavialan, and is also much more rugose.

a) Metriorhynchus b) Steneosaurus
From Martill & Hudson 1991

Metriorhynchus was obviously a highly developed marinehunter that probably preyed on fish, belemnites and any other creature it couldadequately despatch. Some specimens display contents in the stomach region andthese often include belemnite hooklets and also, in one exceptional specimen,the remains of a pterosaur have been identified, probably a carcass that wasfloating on the sea that was snapped up by the passing croc. Two species ofMetriorhynchus are currently recognised from the clay and these are M.brachyrhynchus and M. superciliosus.

Marine crocodiles are often passed over in favour of themore famous reptilian inhabitants of the Callovian Sea but they are as equallyfascinating and not to be underrated. Indeed, I have just been very privilegedto see two skulls from these animals undergoing conservation at the NaturalHistory Museum in London – both from the Leeds collection and what big skullsthey are! Steneosaurus may have been gavial-like in existence but this was aserious hunter and could obviously take quite large prey. Some of its teeth aremuch bigger than the ones I’ve seen from clay and this was an eye opener forme. The skull of Metriorhynchus is massively constructed and obviously powerful– indeed I was surprised how massive it was – and it appears that it too wouldbe very capable of tackling large prey.

This is a very brief introduction to these superbly adaptedanimals and I would like to think that we will be able to extract anotherspecimen of these superb crocodilians from the Oxford Clay at some point in thefuture.

Season’s Greetings!

I would just like to take the opportunity to wish all myfriends, colleagues and all of you who have taken the time to read my blog thisyear a very happy Christmas and hope you all enjoy a wonderful festive season.

Reference

Martill, D.M & Hudson, J.D 1991. Fossils of theOxford Clay. ThePalaeontological Association, London, UK

Uncovering Spinops

2011-12-15T12:46:00.000Z

As most of you are all aware, there was yet another newceratopsian announced last week and Spinopssternbergorum has now taken its place amongst a plethora of recentlyannounced horned dinosaurs. I’ve known about Spinops’ existence for some timenow, for reasons which will become apparent, and I was very pleased to finallysee the official announcement last week. I love the way that news of newlyannounced dinosaurs travels across the globe almost instantly these days andthe buzz created is palpable.

I first became aware that there was possibly a newceratopsian in the vaults of the Natural History Museum in London (NHM) back in2007. I’d met Mark Graham during thesame year, whilst prospecting at Misty Bluff Quarry and we soon became goodfriends. Mark, at the time was a volunteer preparator at the NHM and told methat he hoped to be commissioned to prepare some “unusual” ceratopsian materialthat, although it looked initially a bit like Styracosaurus, could actuallyrepresent a new species.

I was intrigued and at the same time that Mark began lookingat the material, a revision of the type specimen of Styracosaurus albertensiswas published near the turn of the year (Ryan et al 2007) and thinking that itwould be of help, I sent a copy off to Mark. I was too late – Mark had alreadyreceived it and was already engrossed in it! Things started to move on.

In June 2008 Mark commenced work on the specimen and, in hisown words:

“The specimens (which were from a bone bed) were prepared byme in 2008/09 and the two large parietal elements were encased in extremelyhard iron-rich matrix and heavy plaster of Paris jackets. The bone itself was significantlyfractured - so much so that the combination of unyielding rock and fragile bonemade for an interesting (not to say nerve-wracking at times!) project. The imagesshow some of the preparation work and protective jacketing made for thespecimens, together with a couple of images from the last day, in March 2009,when it was all completed.

A particular challenge was the removal of matrix from aroundthe cores of the pro-curved parietal hooks, which actually displayed somelovely detail, and also from around the epiparietal, which was dangerouslythin.

I’m thrilled that my first involvement with a scientificpublication should be on such a significant specimen as Spinops.”

I am personallydelighted for Mark, not only because he is a damned good preparator, butbecause he really is a nice guy and deserves his joint authorship. I hope it isthe first of many for him. Incidentally, Mark is also involved in theinstigation of a new volunteer programme at the NHM and the first workers havenow begun preparation of sauropod material collected in the 1980’s and, as Markpoints out:

“Another “new”dinosaur may soon see the light of day!”

Amen to that!

Note

The images here arereproduced with permission and are not to be used elsewhere without consent.

References

A new centrosaurine from the Late Cretaceousof Alberta,

Canada

,and the evolution of parietal ornamentation in horned dinosaurs. Andrew A.Farke, Michael J. Ryan, Paul M. Barrett, Darren H. Tanke, Dennis R. Braman,Mark A. Loewen, and Mark R. Graham. Acta Palaeontologica Polonica 56 (4), 2011:691-702 doi:10.4202/app.2010.0121

Ryan, M.J., Holmes,R., and Russel, A.P. 2007. A revision of the late Campanian centrosaurineceratopsids genus Styracosaurus from the western Interior of North America.Journal of Vertebrate Paleontology 27: 944-962.

A Pterosaur Revealed.....

2011-12-08T12:13:00.000Z

As highlighted here previously and, as promised, here is the pterosaur Rhamphorhynchus muensteri in all its glory and what a spectacular specimen it is. This particular specimen, of course, is from the Upper Jurassic lithographic limestone of Solnhofen in Germany, around 155 million years old, and is arguably one of the finest examples of its kind ever recovered.

As I mentioned in my previous SVP report, the levels of preservation in the Solnhofen quarries are often spectacular. The limestones were laid down in lagoons that became cut off from the sea as coral reefs rose from the sea floor. It seems likely that salinity increased as a result and these isolated lagoons became toxic and depleted of oxygen which, although not very good for life at the time, proved to be excellent news for palaeontologists.

Any organism that ended up dead in the lagoons would have sunk softly into the muds and, because the isolated toxic environment prevented the carcasses being disturbed or dismembered, the preservation of many fossils is exquisite hence my previous comments regarding the somewhat problematic suggestion that R. muensteri may have displayed a sagittal cranial crest.

However, back to this fantastic specimen and some detail. The overall wingspan of this pterosaur is 725mm and the skull is 100mm long. Bone preservation is incredible and the vertebral processes remain intact – in fact all of the bone in this specimen is exactly as prepared and there are no composite pieces whatsoever. The preparator has done an excellent job.

However, there is a sting in the tail regarding this specimen and that is the fact that it is held in a private collection and I am not sure if it will ever be made available for study or public display. This is unfortunate and, as you are all aware, somewhat commonplace these days which is why I have kept these images for future reference. That still doesn’t take away the fact that this is a quite wondrous and superb specimen.

Coming next – a Spinops exclusive!

SVP 2011 - And Finally.....

2011-12-04T16:07:00.001Z

This is the last of my SVP 2011 reports and I’m very grateful for the positive feedback that I’ve received from so many of you. This last batch of entries represents research across a variety of disciplines but are all equally interesting.

It appears to me that ichthyosaurs are undergoing something of resurgence in popularity and those of the Cretaceous are proving to be not quite as elusive as they were once thought to be. Valentin Fischer has been actively studying these fascinating animals and following on from his recent paper in the Journal of Paleontology, where he announced the new taxonSveltonectes insolitus, he presented more data detailing that ichthyosaurs were still very diverse throughout the Early Cretaceous.

In particular ophthalmosaurids continued to be a very successful group right through the Early Cretaceous. It was initially thought that they had rapidly declined after their initial radiation during the Middle Jurassic but new fossils from Europe and Russia (including Sveltonectes) clearly dispel this theory. It is now apparent that typical Late Jurassic ophthalmosaurs shared the seas of the Eurasian archipelago with typically more derived ichthyosaurs from the same clade such as Platypterygius and that these taxa also appear to be well adapted to fill different niches in the ecosystem.

Staying with marine reptiles, only this time plesiosaurs, and some interesting morphological study of the plesiosaurian body shape by Courtney Richards et al. Comparative studies of three cryptoclidid plesiosaurs– Tatenectes, Cryptoclidus and Muraenosaurus – were performed using a combination of measurements and photographs to correctly position the various bones, such as the vertebrae and ribs etc, which enabled the accurate structural depth and width shape to be attained.

A.Muraenosaurus B. Cryptoclidus
C. Tatenectes (from O'Keefe et al 2011)

To supplement this detail, the vertebrae were also analysed to see if the morphology of the centrum is relevant to the curvature of the spine. Those vertebrae that are most rhomboidal correlate with those areas of the spine that curve the most while those that are less rhomboidal correlate with sections of the spine that are flatter and/or curve less.

Running this data through the computer and subjecting the various structures to lateral rolling suggests that the shallow draft plesiosaurs such as Tatenectes and Cryptoclidus were well suited to shallow waters while those with a deeper draft, like Muraenosaurus, were far more adapted to an open ocean deep water existence.

This is interesting because of its relevance to the Oxford Clay Formation, which has featured heavily in this blog throughout. The sea where the Oxford Clay was deposited was both warm and shallow and conditions were such that vertebrate remains fossilised well and are relatively abundant. Muraenosaurus is a very common genus from these deposits and this does not tie in with the above findings so it will be interesting when this data is formally published. I wonder what the author’s interpretation of deep water is in relation to the Oxford Clay Sea?

One of the symposia this year featured the evolution and ecology of terrestrial ecosystems of Campanian Laramidia. Currently, research in this particular field is incredibly popular and there is enough data around to fill a series of volumes on its own. There are a couple of presentations that I have opted to highlight and one was presented by Mark Loewen et al and discussed the evolution of theropods and how it was affected by geographical boundaries.

In recent years there have been more fossil discoveries from southern Laramidia to complement the already heavily sampled northern fossil fields. Because theropods are less likely to be affected by climatic differences and any change in flora, they were chosen to see if they provide evidence of faunal endemism. Despite the fact that all major groups of theropods are represented from north to south there is no doubt that there were different species represented in different isolated endemic faunas. Tyrannosaurids, as an example, were used to explain that, although they were all large predators that hunted, more or less, the same prey, they still evolved into distinct clades.

Add to this the fact that all these animals all display patterns of diversification and dispersal that are characteristic of those that exist in isolation. These findings seem to confirm what has been suspected for some time now, namely that there was some form of geophysical dividing barrier between north and south Laramidia restricting any obvious faunal exchange. However, just what this barrier was still has to be determined.

From Sampson et al 2010

The second presentation came from, more or less, the same research team – this time with Scott Sampson as lead author. At the time that the Western Interior Seaway split the North American continent into two, Laramidia was isolated for around 25 million years. It has always been assumed, more often than not, that because Laramidia and the corresponding formations of Asia display the same clades of dinosaur, the origins of these clades in North America are as a result of a dispersal event from Asia.

Timing of such an event has been problematic since the Asian formations still have to be satisfactorily radioisotopically dated and now new fossil evidence from the Campanian rocks of the Wahweap and Kaiparowits Formations of southern Utah throws the original dispersal theory into doubt. Specimens of both tyrannosaurid and ceratopsids have been recovered that have been established as the earliest representatives of their kind and this, in addition to stratigraphic, phylogenetic and biogeographic analysis, suggests that it was, indeed, the landmass of Laramidia that was probably responsible for the origins of many taxa in Asia.

The authors suggest that this is unusual since most dispersal events are usually biased in as much that the bigger landmass normally provides the greater faunal exchange and this is particularly true of Cenozoic events. However, Laramidia was a comparatively small landmass compared to the Asian continent and this stands out as being a truly unusual event. There are so many unanswered questions regarding Laramidia that it will continue to attract increased attention and research.

Another symposia this year was devoted to vertebrate diversity patterns and sampling bias and Matthew Carrano and Matthew Oreska, both of the Smithsonian Institute, demonstrated the importance of vertebrate microfossil bone beds. I’m a big fan of these extremely interesting fossil hot spots and the data they provide and, if you have never looked at microfossil sites, then you are missing out – I recommend Julia Sankeys’ work if you are looking for somewhere to start.

The Cloverly Formation of Wyoming and Montana has been worked for around 75 years now and since collecting techniques tend to concentrate on macrovertebrate remains it appears that the overall diversity of the this formation has been overlooked. Reassessment and analysis of the microfossil sites have now added considerably to our knowledge of the animals that once lived in this area during the Early Cretaceous.

The authors report that freshwater sharks, crocodilians and mammals have all been identified with, as is the norm with this kind of analysis, bony fish and crocodilians dominant. But there are significant remains of dinosaurs, amphibians and turtles as well and even after taking proportional representation and other sorting biases into consideration, the results stand up to scrutiny. This is reminiscent of later Hell Creek microsites and is indicative of a wet, aquatic and semi-aquatic environment.

Microfossil bone beds continue to add to our understanding of many palaeoenvironments and, provided the sampling technique is consistent and of sufficient quantity, they are very effective indicators of the different kinds of vertebrate taxa that can be identified in various formations throughout the world.

Now you may remember my teaser image of a rhamphorynchid pterosaur a little while back which will be featuring in my very next blog post and S. Christopher Bennett, of Fort Hays University, has suggested that Rhamphorynchus muensteri may have actually displayed a cranial crest. Although crests for non-pterodactyloid pterosaurs are known, no specimen of Rhamphorynchus has been found with structures preserved that are indicative of a sagittal cranial crest– until now.

A large adult specimen appears to display a series of features on the skull roof that may have formed the base of a soft tissue crest that covers an area measuring about 25% of the skull. Interestingly the author suggests that the majority of R. muensteri fossils are juveniles since there are over 100 specimens in depositories all over the world and not one fossil displays the same features or, indeed, evidence of a crest.

Image by Ryan Somma

This is a very strange and problematic. Preservation of these pterosaurs from the fine grained limestones of such places as Solenhofen is spectacular and specimens of both invertebrates and vertebrates often display the fleshy outlines of wings and body shapes and yet there is not one fossil of R. muensteri that displays any signs of a crest. Even if all the specimens were juveniles, surely there would be one specimen that was at least starting to develop a sagittal crest?

This lack of evidence, for me, is troubling but then the author may correct in his assertion that all the specimens are indeed juvenile. But what would cause such a preservational bias? I’m not too sure but it will be interesting to read the paper on this one and I will look forward to its publication in the future.

And now for my final piece from this year’s SVP and features the ankylosaur Pinacosaurus. Victoria Arbour (of Pseudoplocephalus fame) and Phil Currie, both from the University of Alberta, report on bone beds in Bayan Mandahu, China and Alag Teeg in Mongolia and describe how multiple skeletons that were more or less aligned in close proximity and preserved upright in a miring situation may be indicative of a social group.

Both sites mainly contain the remains of juveniles but at Alag Teeg there is also one large specimen that is certainly an adult. The preservation of the remains is good and taphonomic analysis suggests that this was not groups of animals perhaps gathering together around a dwindling pool in a drought situation. The remains in drought assemblages tend to have their remains scattered and are often badly trampled.

The authors suggest that the ankylosaurs at both bone beds were probably mired in a fairly short space of time by sandstorms or even an alluvial fan. It is possible that the juveniles were accompanied by an adult or adult animals to provide some protection from predators since their osteoderms were yet to develop as well as their tail clubs, which had only partially developed. This scenario suggests that the adult animal(s) were able to pull themselves out of the sand whilst the juveniles could not although obviously, at Alag Teeg, one adult did not escape. It will be interesting when other bone beds are found to see if further evidence and analysis can also suggest the possibility of a social structure in ankylosaurs.

References

Arbour, V. and Currie, P. 2011.Taphonomic filters of age groups on the ankylosaurid dinosaur Pinacosaurus. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp64.

Bennett, S.C. 2011. First evidence of a cranial crest in the pterosaur Rhamphorynchus muensteri. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp69.

Carrano, M. and Oreska, M. 2011. The importance of vertebrate microfossil bonebeds in understanding the fossil record: examples from the Cloverly Formation. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp84.

Valentin Fischer, Edwige Masure, Maxim S. Arkhangelsky & Pascal Godefroit (2011): A new Barremian (Early Cretaceous) ichthyosaur from western Russia, Journal of Vertebrate Paleontology, 31:5, 1010-1025.

Fischer, V. 2011. New ophthalmosaurids from Europe and Russia broaden the biodiversity of Early Cretaceous ichthyosaurs. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp110.

Loewen, M., Zanno, L., Irmis, R., Sertich, J. and Sampson, S. 2011. Campanian theropod evolution and intracontinental endemism on Laramidia. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp146.

O'Keefe, F. Robin, Street, Hallie P., Wilhelm, Benjamin C., Richards, Courtney D. and Zhu, Helen (2011) . A new skeleton of the cryptoclidid plesiosaur Tatenectes laramiensis reveals a novel body shape among plesiosaurs. Journal of Vertebrate Paleontology 31:2, 330-339.

Richards, C., O’Keefe, R. and Henderson, D. 2011. Plesiosaur body shape and its impact on stability. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp178.

Sampson SD, Loewen MA, Farke AA, Roberts EM, Forster CA, et al. (2010) New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism. PLoS ONE 5(9): e12292. doi:10.1371/journal.pone.0012292

Sampson, S., Loewen, M., Irmis, R., Sertich, J. and Evans, D. 2011. Laurasian faunal interchange in the Late Cretaceous: the out of Laramidia hypothesis. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp185.

SVP 2011 - Hadrosaurs & Ceratopsians

2011-11-25T17:43:00.000Z

Research into hadrosaurs and ceratopsians continues to be popular and vibrant and there was some fascinating data discussed at SVP. Prosaurolophus maximus is an understated hadrosaurine from the Campanian of the Dinosaur Park Formation in Alberta but despite being represented by multiple articulated specimens, the taxon has received little attention in the way of both morphological and phylogenetic analysis.

But Christopher McGarrity of the University of Toronto has looked at the cranial characteristics and ontogenetic features closely and found some interesting detail. P. maximus displays an allometric solid nasal crest that, as appears to be so often the case these days, is probably a deirved feature for sexual selection and recognition.

P. maximus, as well as a second species, P.blackfeetensis from the Two Medicine Formation of Montana, were included in a new phylogenetic analysis which recovered the two species as sister taxa and the author states that the morphological differences between the two are hard to quantify and is indicative that P. blackfeetensis is a junior synonym of P.maximus. This suggests that Prosaurolophus has an extended chronological range of 1.6 million years and that is actually a long time when you consider species longevity.

I’ve already mentioned one poster regarding unusual skin preservation in a specimen of Gryposaurus but just why does hadrosaur skin appear to preserve more readily than other dinosaurian taxa? Matt Davis, of Yale University, has provided some detail. Hadrosaurs have been, and continue to be, heavily sampled due to the fact that many Upper Cretaceous Formations are exceptionally well known and it is also the peak period when hadrosaurs were incredibly numerous and diverse. The early 20^th century saw an abundance of hadrosaur skin fossils recovered, especially from the extensive fossil fields of the Cretaceous Western Interior.

They are also nearly always found in sandstone exposures which tend to preserve more hadrosaur skin impressions than other facies. And although hadrosaurs were more abundant than other clades in these exposures, there is still an obvious bias towards hadrosaurian skin preservation. And yet despite these quantative statistics there is still no obvious reason to explain this unusual bias.

Just because hadrosaurs were abundant and the formations they are found in are extremely well known there is still no physical evidence to theorise and account for this unusual skin preservation. One can see that it is not easily explained but the one theory that cannot be ruled out is that hadrosaurs did indeed have some form of morphological skin condition or unusual behaviour that aided this unusual preservational bias.

Everybody is aware that the hadrosaur dental battery was a miracle of evolution and produced one of the most efficient plant processing machines that ever evolved. Greg Erickson and Mark Norell have conducted an extensive histological study of hadrosaur cheek teeth and have found that they were truly complex and even more specialised than mammal teeth. One particular tissue identified on the teeth was coronal cementum and this has actually been proposed as evidence for superior advancement in mammalian dentition. The study provides further evidence and enhances the fact that hadrosaurs possessed a truly remarkable and innovational dental arrangement.

Moving on to ceratopsians and the following focusses, again, on the on going research into dinosaurian synonymy. To begin with is a study of two large “Triceratops” skulls at Brigham Young University by Andrew Beach who re-evaluated the specimens after the very high profile synonymizing of Triceratops and Torosaurus last year. The first specimen, BYU 12183, was unfortunately shown to have extensive restoration and this covered much of the original skull morphology. But the second skull, BYU 19974, has suffered no such remodelling and this turned out to be very much more interesting indeed.

The specimen, which essentially comprises the frill, displays all the ontogenetic markers of an adult Triceratops and yet the parietal is actually thinning down where you would expect to find the parietal fenestrae in Torosaurus. This appears to provide yet more powerful evidence that Triceratops and Torosaurus are the same taxa and the author describes BYU 19974 as an ontogentically transitional form.

Triceratops fossils are remarkably abundant in the Hell Creek Formation and this provides ample opportunity to research gross morphology, ontogeny and phylogeny in this taxon taking into account stratigraphic variability. John Scanella et al have performed just such an analysis focussing on cranial variation in multiple specimens of Triceratops and the results are illuminating and indeed reinforce current thinking and thus open new doors which may affect dinosaur taxonomy as a whole.

It is apparent that ontogenetically identical specimens of Triceratops, even from the same stratigraphic level, can demonstrate astonishing variation. As expected, there is always variation in cranial ornamentation and there are significant morphological differences within individual animals. More surprising is that suture fusion, both within the skull and epi-ossifications, is not necessarily a sign of a mature animal and also that some sub-adult animals are actually bigger than adults. This makes such features unreliable as indication of adulthood. The implications of this are obvious when you consider something like Nanotyrannus where the sutres of the type skull (CMNH 7541) are fully fused and was one of the principle reasons why the taxon was raised in the first place instead of being identified as a juvenile Tyrannosaurus – which is the general consensus today.

Furthermore, histological evidence indicates that even the larger, more mature animals were still undergoing morphological change even at an advanced ontogenetic stage. Many other morphologic variations were revealed by the study and suggest that if other dinosaurs were also subject to the same rapid morphological change then a rapid rethink is necessary when quantifying the amount of dinosaurian taxa in any given formation. Incidentally, the authors report no evidence for sexual dimorphism in Triceratops and suggest that gender recognition was a much more subtle affair and may have been indicated by a visual signal, perhaps even coloration.

From the same stable, and featuring three of the same authors, comes yet more data indicating that it is not just Triceratops and Torosaurus that need to be synonymized. Denver Fowler et al introduce us to unified frames of reference which is a combination of methodologies combining, not only morphology and ontogeny, but stratigraphy, phylogeny, geography and tapohistory.

Not only has Triceratops displayed multiple morphologies at different ontogenetic stages, the same can be said for other chasmosaurines and it appears that both Mojoceratops and Kosmoceratops may both be juvenile morphs of Chasmosaurus sp. and Chasmosaurus irvensis respectively. Similarly, but at the other end of the ontogenetic stage, Titanoceratops displays morphologies that you would expect to find in older specimens of Pentaceratops.

A blast from the past

There are further implications from this research that focusses on biogeographical distribution and faunal endemism and that is currently a very heavily researched and debated subject in the palaeoworld, especially where Laramidia is concerned, and this on-going and important work will make a valuable contribution to our understanding of the diversification of dinosaurs and the environments they inhabited.

References

Beach, A. 2011. Triceratops and Torosaurus synonymy: an evaluation of two large specimens from Brigham Young University. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp68.

Davis, M. 2011. Complete census of published fossil dinosaur integument quantifies taphonomic bias towards prevalence of hadrosaurid skin. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp96.

Erickson, G. and Norell, M. 2011. The histology of hadrosaurid dinosaur teeth – reptiles that exceeded mammals in dental complexity? Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp105.

Fowler, D., Scanella, J. and Horner, J. 2011. Reassessing ceratopsid diversity using unified frames of reference. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp111.

McGarrity, C. 2011. Cranial morphology and variation in Prosaurolophus maximus with implications for hadrosaurid diversity and evolution. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp155.

Scanella, J., Fowler, D., Trevethan, I., Roberts, D. and Horner, J. 2011. Individual variation in Triceratops from the Hell Creek Formation, Montana: implications for dinosaur taxonomy. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp187.

SVP 2011 - Theropods

2011-11-19T16:01:00.000Z

Time for theropods and about time too I hear you say. No matter whoever tries to convince you otherwise, theropods are without doubt the coolest animals ever to walk the planet and, of course, they were strongly represented at SVP.

Did change in theropod skull morphology occur due to the type of prey animals that shared their environment? Richard Bykowski of Indiana University has attempted to answer this question by combining the morphological data taken from the maxillary bones of multiple theropod specimens with the estimated relative abundance of other dinosaurs - including multiple prey animals as well as other theropods.

It appears that there is slight variation in maxilla morphology when the abundance of coexisting animals varies. However, faunas dominated by sauropods display the greatest change whereby the skull becomes more elongate, displays a flatter ventral border and a thickened ramus of the maxilla where it ascends. Other results indicate a lengthening of the snout where there are increased populations of marginocephalians and thyreophorans, and theropods, that shared their environment with larger populations of both ornithopods and other theropods, developed deeper and stronger skulls.

The sauropod result is interesting bearing my recent post about titanosaurs and carcharodontosaurs and Bykowski suggests that the typical carcharodontosaur skull layout is well suited to “slash and run” techniques which, again, I alluded to in the same post. Nice work by the author and I must point out that I have only skimmed the surface of what is obviously an intense and thorough study but I have to say that I would have thought that a sampling bias, in either direction, would probably affect results.

Any material from the mid-Cretaceous that transcends the early to late Cretaceous faunal changeover is rare and when it consists of new theropod material as well then it is doubly important. Derek Main et al have revealed new theropod specimens from the Arlington Archosaur Site in north Texas which comprises of a fauna that inhabited the Cenomanian coastal delta plains and comprise of multi-sized taxa, from the small to the large.

What makes this fauna so special is that it includes both basal tetanurans and dromaeosaurids which are representative of both early and late Cretaceous communities - transitional. Why were basal tetanurans, which originated from Gondwana, still around at this point? It seems that there was a global semi-arid climate that extended from Texas right through to Morocco and Niger and is indicative that these tetanurans preferred this drier environment and this also explains their presence in this transitional mid-Cretaceous fauna.

Study of this unique fauna continues and it is hoped that it will shed more light on both palaeogeographic and palaeoclimatic questions during this crucial period in the Cretaceous. Of particular interest is how Gondwanan land faunas made the dispersal across the Berentsian land bridge and when this occurred since the Arlington fauna suggests an earlier crossing than initially thought.

Ornithomimus is one of best known ostrich-like dinosaurs and it is good to know that the holotype, Ornithomimus velox, is indeed a confirmed and valid taxon. Leon Claessons et al have reappraised the type material, which comprised of a distal tibia, partial pes and a partial manus, and performed a detailed examination which was enhanced by the fact that the material had been properly prepared and freed from matrix for the first time in over one hundred years.

Comparing the type material with specimens of Ornithomimus edmontonicus has shown the two genera to be similar but O. velox has slightly longer metacarpals although the pes of O. edmontonicus are longer overall but not a as robust. There is also an unusual development in the metatarsals and that is metatarsal II is longer than metatarsal IV which no other ornithomimid displays.

But the authors point out that a specimen from the Campanian Kaiparowits Formation of Utah has a similar condition and since there is a ten million year age gap between it and the purely Maastrichtian O. velox then it is apparent that O. velox is valid. Incidentally, the fossils from the Kaiparowits display morphological differences that infer that there are at least two as yet unnamed taxa from this formation.

Michael D’emic has featured a few times in recent posts and this time, with lead author Keegan Melstrom, both from the University of Michigan, have reported on a partial skeleton of a juvenile Acrocanthosaurus atokensis that has been recovered from the Cloverly Formation of Wyoming – the first time that this allosauroid has been identified in this formation.

The specimen has provided further data revealing that these theropods also grew fast at similar rates to tyrannosaurids and would reach adult size somewhere between 20 – 30 years old. Acrocanthosaurus represents one of the basal Gondwanan forms that was referred to earlier in the post and appears to have been widespread leading up to the early/late Cretaceous transitional stage.

A few years ago I was privy to some research being carried out on spinosaurids and baryonychinines and was told, in no uncertain terms, that it was certain that Suchomimus would be sunk into Baryonyx because they were irrefutably the same taxon. Well in 2011, that appears to no longer be the case. Nizar Ibrahim and Paul Sereno have revealed detail s of some new Suchomimus material which appears to contradict that theory.

The material was recovered from Middle Cretaceous exposures in Niger and includes a complete snout and, for the first time, some braincase material. There are several features, both cranial and postcranial that, according to the authors, settles the argument once and for all that Suchomimus and Baryonyx are, in fact, distinct genera – now where have I heard that one before?

It will be interesting to hear the response from the opposition camp and, as usual, we will all have to wait for the paper. Somehow, I suspect that this is not the end of this saga just yet. On the same poster the authors report on new spinosaur material from the early Upper Cretaceous deposits of Morocco and by comparing this new material with some “original” material from Egypt, they suggest it is likely that there was only one species of Spinosaurus that existed throughout the Cenomanian of Africa.

The quotation marks on “original” are my additions since, according to the abstract, the comparison was with “........the type material of Spinosaurus from Egypt.” And yet it is generally accepted that all of this material was destroyed by allied bombing during the war – so where did this material come from? It will be interesting to find out what this compared material actually is and again we must wait for the paper – the devil is in the detail.

A very popular talk, and discussed already in the palaeoworld by Brian Switek at Dinosaur Tracking and Stu Pond over at Paleo Illustrata, Alicia Cutler et al looked at why and how the classic theropod death pose occurred whereby the head and neck are stretched and arched back almost over the sacrum and the tail stretches cranially over the head and neck.

Since most fossils discovered this way are found in sediments laid down in an aqueous environment, the authors decided to test the theory that submersion would inflate the elongate muscles that lie along the long axis which would shorten them thus creating the familiar contraction. Utilising some novel controlled experiments by submerging plucked chickens in water have provided the authors with startling results.

Astonishingly, once submerged, there is an almost instantaneous reaction by the head and neck muscles that pulls the head back – in some cases almost identically to the positions found in theropod dinosaurs. To make sure of their findings, controlled experiments with chicken carcasses in a dry environment were performed but with no noticeable distortion in over three months.

The team were both surprised and delighted by the results and suggest that movement was also helped by the fact that skull pneumaticity was a contributing factor due its relative lightness. Contraction continues after the initial submersion but only to a slight degree. For me, this is science at its best and I love the nature of these experiments and its simplicity and the team are to be highly commended.

Tyrannosaurs did not feature too much this year – indeed only there were only three technical sessions and one poster this year - of which three refer to T.rex, but the one of most interest, to me, is Thomas Carr’s continued work within Tyrannosauridae. This time Carr focussed on the sequence of development (heterochrony) that led to evolved features (synapomorphies and autapomorphies within tyrannosaurid phylogeny.

Because several species of tyrannosaurids are represented by almost complete ontogenetic life histories it was possible, by using cladistic analysis, to compare these stages and look for evidence of heterochrony. The author did indeed identify heterochrony, especially within tyrannosaurines, highlighting the maxillary fenestra as evidence and suggests that this kind of study is indeed ideal for identifying the morphological processes arrived at via heterochrony.

References

Bykowski, R. 2011. Biting Off More Than They Can Chew: A Geometric Morphometric Approach to Theropod Feeding Ecology. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp81.

Carr, T. 2011. A Comparative Study of Ontogeny Between Derived Tyrannosauroids: Evidence for Heterochrony. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp84.

Claessens, L., Loewen, M. and Lavender, Z. 2011. A Reevaluation of the Genus Ornithomimus Based on New Preparation of the Holotype of O.velox and New Fossil Discoveries. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp90.

Cutler, A., Britt, B., Scheetz, R. and Cotton, J. 2011. The Opisthotonic Death Pose as a Function of Muscle Tone and Aqueous Immersion. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp95.

Ibrahim, N and Sereno, P. 2011.New Data on Spinosaurids (Dinosauria: Theropoda) from Africa. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp130.

Main, D., Noto, C. and Scotese, C. 2011. New Theropod Material from the Cretaceous (Cenomanian) Woodbine Formation of North Central Texas: Paleobiogeographic and Paleoecological Implications. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp150.

Melstrom, K. and D’emic, M. 2011. Acrocanthosaurus atokensis (Dinosauria: Theropoda) from the Cloverly Formation of Wyoming: Implications for Early Cretaceous North American Ecosystems. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp157.

SVP 2011 - Lungs, Legs & Rapid Growth

2011-11-13T17:02:00.000Z

Contributions on dinosaur physiology were well represented at SVP and here are a few that I found interesting. How dinosaurs managed to regulate their body temperature has been debated ad infinitum and this will no doubt continue to be so and, regardless of whether they were endothermic or not, the problem of overheating and how they managed to avoid it has proven difficult to explain.

William Porter and Larry Witmer of Ohio University hypothesised that dinosaurs must have used a form of vascular physiology as a method for heat control. Using a combination of CT scanning and the Extant Phylogenetic Bracket whilst studying dinosaur fossils, and then running the data in a 3D environment, has provided some interesting preliminary results. By comparing these results with similar studies of extant animals, such as birds and reptiles, a vascular anatomical profile of three dinosaurs (Majungasaurus, Edmontosaurus and Diplodocus) was established.

In simple terms, similar osteological correlates were identified in these dinosaurs that are present in the extant taxa examined. This study is at an early stage but further investigatitive techniques, new methodologies and expanding the results by utilising more dinosaurian taxa may provide a more robust and demonstrable dataset.

Today’s birds and crocodiles are in possession of lungs that allow unidirectional airflow but what are the origins of this physiological adaption in archosaurs and is there evidence for it in Triassic and Jurassic archosaurs? Physical evidence of postcranial skeletal pneumaticity (PSP) does not fossilize but traces remain and can suggest the extent of any air sacs that were present which, in turn, may indicate an avian-like respiratory system. Paul Barrett et al used micro-CT scanning on multiple archosaur specimens from the Triassic and Jurassic to search for evidence of PSP - and the results were encouraging.

It seems likely that non-avian saurischians and pterosaurs did indeed possess advanced respiratory systems but the results are less conclusive for ornithischians and other archosaurs. In these specimens there are other features, however, that may be indicative of a somewhat less advanced form of respiratory system and the authors suggest this may also be indicative of an earlier origin for the system, not only in dinosaurs, but throughout the entire archosaurian lineage. Interestingly, it seems, like so many other evolutionary convergences, that different groups of archosaur evolved their own form of respiratory systems and these, in turn, were probably variations on a theme that developed unidirectional airflow, as well as specialised air sacs.

A quick mention now about Heinrich Mallison’s contribution that looks again at how dinosaur speed is calculated and discusses how our original perception of speed that was calculated by using Alexander’s froude number, is outdated and is compromised by far too many inconsistencies. Instead, Mallison uses modern digital models combining SIMM and computer aided design to reach some interesting conclusions. Already discussed at national level at Nature, Mallison is currently explaining his work at his own blog, dinosaurpaleo, and I strongly advise you to visit – great stuff.

Of course, one of the pre-requisites in working out speed and locomotion in dinosaurs is being sure that your limb posture is correct in the first place but things are seldom that easy in vertebrate palaeontology. Forelimb posture in quadrapedal dinosaurs continues to stimulate debate with ceratopsians often at the forefront of discussion but the problems are much broader than that. Where and how do you start to sort this problem out?

Well you need radii, lots of them, 380 in fact and then you have to perform a painstaking morphological study and quantify them before comparisons can be made – and this is what Collin Vanburen and Matt Bonnan of Western Illinois University have done. The sample included radii from mammals and sauropsids, as well as dinosaurs, and this provided the ability to test the theory that, if dinosaurs had an erect limb posture similar to mammals, then it should follow that the shape of the radius would be similar as well.

However, the results suggest that dinosaurs and mammals are not alike at all – in fact they are actually more similar to non-erect sauropsids. And ceratopsians were hugely different from mammals, which substantially challenges the suggestion that they were able to run and charge like extant rhinos. The radii of sauropodomorphs, typically of the group, resemble neither radii from both mammals and sauropsids and have their own distinct morphology which suggests that they may have held their forelimbs erect but in a very specialised manner.

The authors conclude by stating that it seems likely that the majority of quadrapedal dinosaurs held their forelimbs in a non-erect posture and that it is best not use the mammal analogy as a basis for further study, whether assessing dinosaurian speed, gait or posture.

The study of bone histology was at the very forefront of the dinosaur revolution back in the seventies and continues to yield yet more data in support of active, high metabolic dinosaurs. Some of the latest information is provided by Koen Stein and Martin Sander of the Steinmann Institut fr Geologie in Bonn, Germany and concerns different cellular density in fibrolamellar bone.

Cellular density is measured by studying something known as osteocytes and these exhibit distinct patterns and morphologies that allow them to be quantified. By comparing the osteocytes of mammals and saurischians dinosaurs, including both sauropods and large theropods, it was possible to compare the two and then expand the analysis by also including extant poikilotherm ectotherms.

Saurischian dinosaurs have a much higher osteocyte density than mammals of comparable size and, likewise, mammals have a much greater density than ectotherms. Since mammals are high metabolic endotherms then the study suggests that dinosaurs had different ways of building fibrolamellar bone. High osteocyte density that is so much greater than ectotherms also provides powerful evidence for sustained active, high metabolic saurischians dinosaurs.

I have merely skimmed the detail of the top of this fascinating work and it provides the foundation for further studies of osteocyte density within the greater framework that is bone histology and physiology. And, of course, yet more evidence that supports the already huge amount of data that tells us that dinosaur were fast growing, high metabolic animals.

References

Barrett, A., Butler, R., Gower, D. And Abel, R. 2011. Postcranial Skeletal Pneumaticity and the Evolution of Archosaur Respiratory Systems. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp66.

Mallison, H. 2011. Fast Moving Dinosaurs: Why Our Basic Tenet is Wrong. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp150.

Porter, W. and Witmer, L. 2011. Vascular Anatomy and it Physiological Implications in Extant and Extinct Dinosaurs and Other Diapsids. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp176.

Stein, K. And Sander, P.M. 2011. Osteocyte Lacuna Density in Saurischian Dinosaurs and the Convergence of Fibrolamellar Bone in Mammals and Dinosaurs: Different Strategies to Grow Fast. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp199.

Vanburen, C. and Bonnan, M. 2011. Quantifying the Posture of Quadrapedal Dinosaurs: A Morphometric Approach. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp208.

SVP 2011 - Sauropods

2011-11-10T18:11:00.000Z

Sauropods continue to generate enormous interest and at this SVP meeting it was no different – and rightly so. They are the giants of the dinosaurian world but it is not always the biggest that is at the forefront of sauropod study and an ontogenetic series of the dwarf sauropod, Europasaurus holgeri, has provided new data on how dwarfism in dinosaurs evolved due to island isolation.

Oliver Wings of the Museum fr Naturkunde Berlin also revealed that the Langenberg Quarry in Northern Germany has provided an extensive vertebrate fauna that includes not only Europasaurus, but pterosaurs, crocodiles, turtles and fish. The focus of the study is to take into account the stratigraphy, taphonomy and palaeoecological considerations in combination with the taxanomic and palaeobiogeographic evidence to be able to identify what determined island dwarfing in dinosaurs.

Moving on to a “proper” sauropod and Kelli Trujillo et al reported on a specimen of Camarasaurus that may not be all that it seems. The specimen was recovered from a bonebed in the Upper Jurassic Morrison Formation of Albany County, Wyoming and took the team by surprise since, although the animal was quite large, it displayed characteristics that suggested it was actually a juvenile.

The specimen is made up of mainly caudal vertebrae, a few dorsals and the sacrum and since camarasaurid growth stages are recognised due to the degree of neurocentral suture fusion, this specimen can be recognised as a juvenile because a large proportion of the vertebrae are unfused. But the size of the bones are of an animal approaching 90% of a regulation sized adult Camarasaurus – and therein lays the dichotomy.

Another anomaly is the fact that this camarasaurid is perhaps one of the oldest known specimens of the genus. Perhaps the animal is one of those strange aberrant individuals that cause so much phylogenetic and taxanomic distortion when they are found. The authors will continue their research into the specimen and they also suggest that this animal may indeed be a new larger species of Camarasaurus, which would be really interesting.

Already mentioned in the blogosphere is the discovery of a partial titanosaur caudal vertebra that can be regarded as the first definitive record of sauropods from Antarctica. Ignacio Cerda et al reveal that the specimen was recovered from the Late Cretaceous (Campanian) of James Ross Island and extends the range of South American titanosaurs beyond the continent and represents the southernmost example of a sauropod ever found.

Back to the Morrison Formation and just how the vegetation that grew during the Late Jurassic managed to sustain such a vast population of giant sauropods, as well as other mega-herbivores, remains unclear. Until recently, it has remained a matter of uncertainty as to even what plants dominated the Morrison landscape but now Carole Gee, from the University of Bonn, may have provided a few of the answers.

Traditionally, the Morrison flora has been depicted as either fern dominated or something akin to the savannahs of Africa today, with a limited distribution of trees that were somewhat restricted and isolated in number. The fact that fossil wood and logs are commonplace in the formation seems to have been disregarded. But now a combination of the discovery of many new species of conifer cones, in tandem with pollen samples recovered throughout the Morrison, has shed new light on the true nature of the Late Jurassic flora.

The results suggest a landscape dominated by conifer forests that were interspersed with plants such as moisture loving ferns and these would have been able to provide a much greater quantity of fodder for the mega-herbivores as opposed to, for example, a savannah-like environment.

Nutritional analysis of similar extant analogies of the fossil plants suggests that they were also much more nutritious than previously thought and were well suited to the dietary needs of sauropods. When you consider the amount of fodder an adult sauropod would require on a daily basis, estimated to be in the region of between 1000 to 2000Kg, then this was just as well. It also supports the suggestion that sauropods were r-strategist breeders enabling juveniles to reach large sizes very quickly due to this extensive, and very nutritious, vegetation.

I mentioned during my post about Alamosaurus that there was more data in the pipeline regarding this enigmatic sauropod and Jeffrey Wilson and Michael D’emic of the University of Michigan provide it. They confirm that the holotype scapula is indeed diagnostic and that this enables several more specimens, that are much more complete, to be referred to Alamosaurus. This, in turn, expands the overall diagnosis for the taxon and new phylogenetic analysis recovers Alamosaurus as a derived titanosaur with either Asian or South American affinities. This appears to confirm that Alamosaurus was indeed an immigrant as opposed to being a member of Early Cretaceous North American sauropods that appear after surviving the so called 30 million year long sauropod hiatus.

References

Cerda, I., Paulina Carabajal, A., Salgado, L.,Coria, R. and Moly, J. 2011. The First Record of Sauropod Dinosaurs from Antarctica. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp86.

Gee, C. 2011. Sauropod Herbivory During Late Jurassic Times: New Evidence for Conifer-Dominated Vegetation in the Morrison Formation in the Western Interior of North America. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp115.

Trujillo, K., Demar, D., Foster, J. and Bilbey, S.A. 2011. An Exceptionally Large Juvenile Camarasaurus from the Morrison Formation (Upper Jurassic) of Albany County, WY, USA. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp205.

Wilson, J and D’emic, M. 2011. The Validity and Paleobiogeographic History of the Titanosaur Sauropod Alamosaurus sanjuanensis from the Latest Cretaceous of North America. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp215.

Wings, O. 2011. Beyond Europasaurus: The Late Jurassic Vertebrate Assemblage of the Langenberg Quarry in Oker/Germany. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011, pp215.

SVP 2011 - Some Highlights

2011-11-06T16:46:00.002Z

So SVP is over for another year and, embargoes now lifted, we can report on, and discuss, some of the excellent content that was presented in Las Vegas. Here I report on some of the highlights that, from a purely personal point of view, are amongst the most fascinating.

One of the most famous dinosaurs in recent years is a specimen of Thescelosaurus neglectus known as Willo who made worldwide headlines as possibly being the first dinosaur found with a fossilised four chambered heart. Naturally this has led to some controversial discussion as to whether the structure located within the thoracic cavity is actually what it appears to be.

But now, following on from his previous work (2011), Timothy Cleland of North Carolina State University has performed an extensive morphological examination of the specimen and has demonstrated that the “heart” of this dinosaur is almost certainly a geological artefact. However, there is also evidence of structures that are not conducive with being of geological origin and are actually similar to both plant and animal cells. Further examination using scanning electron microscopy suggest a biological origin for these structures which is somewhat intriguing although the overall evidence from this intense study overwhelmingly supports a geological origin for the structure.

Direct evidence of predator-prey relationships in the fossil record is always fascinating and brings the prehistoric world to life. Evidence of predation on fossil bone is more common than people realise and to see the serration and gouge marks, sometimes so clear on the surface of bone, is always a thrill. But now a specimen of Microraptor, from the Early Cretaceous of China, has taken this interaction to another level.

O’Connor, Zhou and Xu of the Institute of Vertebrate Palaeontology & Palaeoanthropology (IVPP) in Beijing reveal that the specimen appears to have the remains of an enantiornithine bird in its stomach. The authors suggest that Microraptor did indeed hunt in the tree canopy since the birds were obviously arboreal. And, the authors also suggest, that this may be further evidence for a “tree down” origin for avian flight. Looking forward to the paper being published for this one.

The Morrison Formation is one of the most heavily sampled vertebrate bearing strata in the world and is rightly famous for providing a multitude of Late Jurassic dinosaurs. But there is also a varied mammalian community that is not so well known but is equally as fascinating and now Anthony Martin et al have revealed a wonderful discovery that captures one of those unique moments in time.

A quarry near Bluff in Utah has revealed an extensive network of burrows that have been dug by fossorial mammals probably weighing as much as 500gm – quite large for the time and represents an as yet unknown taxon. It is a typical burrowing system with main tunnels, side offshoots and various chambers and, amazingly, some of the smaller tunnels wind through and around the skeleton of a camarasaurid sauropod skeleton.

Palaeoenvironmental studies reveal that the sauropod had died millennia before in a waterhole environment and was buried in sediment and detritus. Eventually, the site was covered in newly formed soil as a result of pedogenesis. It was this soil that was tunnelled through by the mystery mammals who gradually penetrated through to the sauropod skeleton. The burrows within the skeleton actually change direction to get around the bones demonstrating how the mammals were affected by the obstruction. A wonderful and rare discovery capturing, indirectly, mammalian and dinosaurian interaction during the Jurassic.

Back in August, Robin O’Keefe and Luis Chiappe announced in Science that a specimen of Polycotylus latippinus, recovered from the Pierre Shale in Logan County, Kansas, was found in association with, what they describe as, embryonic remains of a juvenile. At SVP there was yet more detail displayed describing the specimen and shows that the bones of the juvenile are poorly ossified and are at an early ontogenetic stage.

The fact that the bones of the juvenile were found within the body cavity of the larger specimen and that they show no sign of being digested or chewed leads to the conclusion that this specimen of Polycotylus was a gravid female that died prior to giving birth. It is apparent that the embryo still had a period of significant development to undergo before coming to term and it appears likely that Polycotylus gave birth to single, very large new borns.

Strangely, you would think that there would have been other specimens of pregnant plesiosaurs found by now, especially when you consider how many plesiosaurs have been collected over the years. Perhaps the most interesting part of this discovery is the hypothesis, because a single birth by implication suggests as much, that plesiosaurs may have demonstrated parental care for their young which in turn leads to suggestions that they also engaged in a form of social structure and interaction. This leads to all sorts of new conjecture and may redefine how we interpret reproductive and behavioural patterns in other marine reptiles.

Finally, here’s one for you palaeoartists out there and is amazing in its own right. A hadrosaur, tentatively referred to Gryposaurus, recovered from the Upper Cretaceous Kaiparowits Formation of southern Utah has revealed some unique and illuminating skin impressions displaying previously unknown morphologies.

Katherine Clayton et al have demonstrated that there is a single line of large scutes that sit proud along the dorsal ridge of the tail - totally unknown before now. On the flank of the tail, it is apparent that the skin tubercles are bigger dorsally at the proximal end whilst distally the largest tubercles are situated ventrally. The tubercles themselves are polygonal and irregular in size and display various lines of ridges that terminate in a scalloped edge that are non-uniform. This find is comparable to other skin impressions found in this and other similar formations but is quite distinct from other hadrosaurs such as Edmontosaurus.

References

Clayton, K., Irmis, R., Getty, M., Lund, E. and Nicholls, W. 2011. An Exceptionally Preserved Hadrosaurid Dinosaur Skeleton with Integument Impressions From The Upper Cretaceous Kaiparowits Formation of Utah. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011,pp90.

Cleland, T., Stoskopf, M.K. and Schweitzer, M.H. 2011. Histological, Chemical, and Morphological Reexamination of the “Heart” of a Small Late Cretaceous Thescelosaurus. Naturwissenschaften 98: 203-211.

Cleland, T. 2011. Chemical and Morphological Reinvestigation of the Dinosaur Heart. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011 pp90.

Martin, A., Noto, C. and Chiappe, L. 2011. A Burrow Runs Through It: Unusual Co-occurrence of a Large Mammal Burrow System and Dinosaur Skeleton in the Morrison Formation of Utah. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011 pp152.

O’Connor, J., Zhou, Z. and Xu, X. 2011. Small Theropod with Bird in Stomach Indicates Both Lived in Trees. Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011 pp168.

O’Keefe, F.R. and Chiappe, L. 2011. Viviparity and K-Selected Life History in a Mesozoic Marine Plesiosaur (Reptilia: Sauroppterygia). Science 333, 870-873.

O’Keefe, F.R. and Chiappe, L. 2011 Viviparity and Cetacean-Like Life History in a Mesozoic Marine Plesiosaur (Reptilia: Sauropterygia). Journal of Vertebrate Paleontology, SVP Program and Abstracts Book, 2011 pp 168.

How Big a Bite is Big?

2011-11-03T13:06:00.000Z

So Planet Dinosaur has now finished its six episode run and I think it fair to say that the series has been generally well received by both the general public and the palaeoworld as a whole. It was my intention to review the series but I think Marc Vincent has done an excellent job of that over at Love in the Time of Chasmosaurs and presents a reasonable and balanced view. Head over there and take a look if you haven’t already done so.

In one episode, New Giants, there is a sequence depicting a group of Mapusaurus attacking a group of Argentinosaurus and at a one point we witness one of the theropods removing great slices of flesh from the flanks of a distressed, what appears to be, sub-adult sauropod. The theropods withdraw leaving the unfortunate beast with great wounds that bleed profusely and it is intimated in the narration that the sauropod is slowly being reduced to a moving feast as the attackers return again and again to take yet more flesh from the slowly dying animal. But how possible or realistic is this?

Carcharodontosaurid teeth are flat, blade-like and heavily serrated making them ideal cutting tools and are well suited, it would appear, of removing significant amounts of flesh from prey animals. Mapusaurus was a big theropod, comparable with Tyrannosaurus, with a massive skull and powered with significant jaw muscles and it is likely that Mapusaurus was very capable of taking huge bites out of sauropods. Or was it?

From Coria & Currie 2006

Just how thick the skin of sauropods was must remain a matter of conjecture but it is safe to state that it was considerable. The hide of an elephant maybe up to 100 to 125mm thick in some places so it seems reasonable to assume that a sauropods’ skin would have been thicker by an undetermined amount but, for the sake of argument, lets imagine it to be in the region of 150 to 200mm thick which does not appear to me to be unreasonable.

We have some skin impressions of sauropods which display a conventional scale covered surface and, in the case of some titanosauriformes, is supplemented by raised and not insignificant osteoderms (e.g. Bonaparte 1999). Just how durable all this makes the skin is conjecture but this appears to me to represent one hell of a tough mouthful for an attacking Mapusaurus to contend with. The skin alone is probably thicker than the teeth are long and you have to remember that carcharodontosaurid teeth are essentially flat and narrow, even if the crowns are approaching 125mm in length, and do not have the power or durability of, for example, tyrannosaurid teeth. Although theropod teeth were constantly being replaced throughout their lifetime, it seems likely that any theropod would prefer not to lose too many at any one time.

Even if there were no osteoderms, obtaining a mouthful of flesh for the theropod is problematic. The sauropod is certainly not standing around allowing the carnivores to attack at will and will be a moving target, albeit a slow one, and has the added bonus of a significant mass and tonnage which the attacker would do well to avoid.

Looking at other possibilities, maybe there were more vulnerable areas to attack such as the neck but this would be a constantly moving target and it would also be capable of generating significant force that may inflict substantial damage on any attacker. However, as already stated, the teeth of carcharodontosaurids are excellent cutting tools and maybe they were used simply to cut the skin, perhaps supplemented by claws from both the manus and pes, to get the sauropod bleeding as much as possible. Constant hit and run attacks in this way would be an efficient and safer option for any attacking theropod as opposed to trying to tear out great chunks of flesh - slash-and-dash as it is often referred to.

The other tool in the theropods tool box is the fact that they were much faster and agile than any sauropod could possibly be and should be capable of side stepping any flailing neck or tail (remember that we are discussing titanosaurs – not diplodocoids). Having said that, if sauropods moved in herds then it seems possible that they may have defended themselves as a collective group and then the problem is amplified for the attacker and they would need every ounce of agility to avoid injury.

Image from Planet Dinosaur © BBC

All of this assumes that large theropods such as Mapusaurus actively targeted sub-adult and adult animals but this was almost certainly not the case unless one such animal was sick or injured. In such cases as these, the hunters could probably take their time with their assault since the unfortunate beast was almost certainly on its way out anyway. It appears obvious to me that even the largest of theropods would take the easier options of softer targets such as the weak, the sick, the young and, of course, any carrion that they came across.

One thing this particular episode of Planet Dinosaur probably got right were the high mortality rates of young sauropods at the nesting grounds. Using the famous titanosaur nesting ground of Auca Mahuevo as the setting, the episode showed pterosaurs and the abelisaurid Skorpiovenator plundering the nests of the young hatchlings and it seems obvious that the annual? sauropod nesting season would have attracted every predator for miles to join in on the feast and I would include the giant carcharodontosaurs in on this.

Nesting sites such as Auca Mahuevo suggest that sauropods were almost certainly what are known as r-strategists (Chiappe 2003). That is that they laid vast quantities of eggs producing young sauropods that, although tiny in comparison to the adults, were able to survive on their own – if they lived long enough to do so. Mortality rates would have been enormous but those that survived would have grown rapidly and got relatively big very quickly although it would still have taken several years to become a giant. This would have meant that there would have been many different generations of sauropod in circulation at any one time and these animals were likely to be those favoured by theropods – including the giants such as Mapusaurus.

Of course, all of this still has to be considered speculation and it seems likely that very few sauropods would attain their full adult size due to predation but if sauropods were herding animals that grouped together for protection then there may have been an element of sanctuary within the herd for some juveniles at least.

References

Bonaparte, J. F., 1999. An armoured sauropod dinosaur from the Aptian of northern Patagonia, Argentina, pp. 1–12 in Tomida, Y., Rich, T.H., and Vickers-Rich, P. (eds.), Proceedings of the Second Gondwana Dinosaur Symposium.

Coria R. A. & Currie P. J. 2006. — A new carcharodontosaurid (Dinosauria, Theropoda) from the Upper Cretaceous of Argentina. Geodiversitas 28 (1) : 71-118.

Chiappe, L.M., Coria, R.A., Jackson, F. & Dingus, L. 2003. The Late Cretaceous Nesting Site of Auca Mahuevo (Patagonia, Argentina): Eggs, Nests & Embryos of Titanosaurian Sauropods. Palaeovertebrata, Montpellier, 32 (2-4): 97-108.

SVP 2011 is Here!

2011-10-30T20:16:00.000Z

It’s that time of year again and all roads lead to Las Vegas for this year’s 71^st SVP meeting - and what an event it promises to be. The meeting is quite possibly the biggest one of its kind and I cannot remember seeing so many talks and posters at the one conference – especially the posters and Heinrich Mallison alludes to this over at dinosaurpalaeo.

There is so much of interest this year and so much to discuss but, of course, any discussion about content of the meeting is embargoed until the posters and talks actually begin. That’s fair enough and we should all be use to that by now but I will be highlighting some of those talks and posters that are really interesting over the next few weeks and, I promise you, these will only scrape the surface of the amount of data being presented at this year’s SVP.

I’m quite sure that many of you are already en route and that many will be leaving imminently. To all my friends and colleagues attending this year’s meeting – I hope that the event lives up to your expectations and hope you all have a great time!

Humerus Preparation Finished

2011-10-27T12:23:00.001+01:00

Sticking with all things Oxford Clay and I’m pleased to reveal the fully prepared humerus of our mystery plesiosaur – and what a fine example it is. Although the bone was in pretty good condition when it was recovered, it was in two pieces and slightly scraped at both the dorsoproximal and distal ends. This was a clean fresh break that was almost certainly caused by an excavator as it passed overhead and this was almost certainly the same machine that uncovered the specimen in the first place – a double edged sword so to speak.

To be able to look at the finer detail of the bone it was obviously necessary to remove the matrix that was adhering to the specimen. It was also a requirement that the two pieces be stuck together and, since the specimen was densely mineralised and heavy, the join would have to be of considerable strength.

Because of the nature of the matrix and its “stickability”, a variety of different tools were used on the preparation and the form of the matrix dictated what tool was to be used. The amount of matrix removed mechanically was very small and primarily revolved around the proximal end and distal flange whilst the bulk matrix on the shaft and flange were removed with various hand held tools. This was necessary because some sediment tends to blend in with the bone and the external patina is easily damaged if you are not extremely careful.

One problem that I’ve not encountered with material from the clay is knowing where matrix ends and bone begins - unlike some other material I’ve been preparing. It is easy to differentiate unless you make the mistake of going too deep in the first place – then you can have a problem but, if you are careful, then mistakes should be rare. Some Triassic skull material I’ve been working with, on the other hand, is almost identical to the surrounding matrix and is slow going.

Although the bone was tough, it still needed support throughout the preparation process and I used small sand bags in combination with mutil-layered bubble wrap to provide it. The humerus has needed very little in the way of consolidation although it has been given a gentle protective coat of Paraloid B-72 and this has also been used to glue the two parts of the bone back together at a 50/50 solvent to consolidant ratio. This has made for an extremely tough bond and appears very robust.

The shaft of the humerus was stood in a container of sand which effectively held it in place and upright and, once the glue had been applied, the flange was very quickly joined on and held in place by various bits of ethafoam, which not only held the bone in place but also allowed for adjustment. The join was so perfect that I used the weight of the flange to create the pressure required and then left it for 48 hours to really harden.

The join appears to be excellent and is likely to be strong enough but if it is found to be wanting then I can always redo it and will probably add glass beads which would form an even stronger bond but I really don’t think it will be necessary in this case.

Next up is the ulna (below) and then the radius, which shouldn’t take too long to prepare and then we will be into the proximal carpals – the ulnare, intermedium? and radiale and, after that, the distal carpals.

The Other Oxford Clay Fauna

2011-10-20T13:01:00.000+01:00

The Oxford Clay Formation in England has yielded a diverse community of marine reptiles and fish for well over 150 years now and has featured in this blog many times, as regular readers will know. What does not get mentioned so often is the fact that there is also a significant invertebrate fauna, trace fossils and, as I have mentioned previously, plant fossils.

The bed that we study most intensely is known as Bed 10 which is Middle Callovian in the Lower Oxford Clay – more familiarly known as the Jason Zone. Bed 10 is at the very base of the clay quarries that have been dug out over recent years and is as far as excavations take place. This is primarily due to the fact that the bed is full of concretions that would easily damage very valuable machinery and interrupt the brick making process.

The other issue would be the fact that further penetration would break into the underlying Kellaways Formation that has no commercial value although this formation has produced some excellent vertebrate fossils where it has been exposed on occasion. The only other excavations into Bed 10 are to dig drainage ditches which help control the water level in the quarries although these are not as common as they once were. This is unfortunate since many excellent finds have been made in and around these ditches over the years.

The most abundant fossils in the clay, that are readily apparent to the naked eye, are the ammonites and these are dominated by the Kosmoceratidae – specifically Kosmoceras jason, from which the zone epithet is derived, but there are others represented such as K. medea and other species such as Sigaloceras. Preservation of ammonites, in these quarries, is often spectacular to look at in the clays and shales but are impossible to collect since they are nearly always crushed flat and are wafer thin. They can occasionally be found in three dimensions in nodules but, again, are almost impossible to extract.

Belemnites are also abundant and, on occasion, are spectacularly preserved. These, in contrast to the ammonites, are easily collected since the rostra fossilise well. Belemnite rostra, like the nodules, also cause problems for the brick makers and will often explode in the curing process so they are always removed where possible.

The most common species are Cylindroteuthis puzosiana and if you are fortunate to visit a quarry after fresh clay extraction, then you can find many undamaged rostra in superb condition. Some are giants, approaching 25cm long, but are more likely to be 15 – 20cm long although you can find some that are as small as 25mm as well. Fragments suggest even bigger specimens exist but these are very elusive and it is apparent that their size and length make them vulnerable to extreme damage.

Cylindroteuthis (left) & Belemnopsis (right).

Phragmacones are fairly common and, every now and then, you can observe the badly preserved outline of the soft parts at the head of the animal, including the tentacles, in the clay. Hooklets are occasionally found but I personally have yet to see one. The other locally common species, Belemnopsis bessina, is much smaller with the rostra probably reaching a maximum of 75 to 80mm and these are sometimes mistaken for fish bone.

Crustaceans are present in the shales and are meant to be locally abundant, especially at the top of the Jason zone, but I have never seen one until this year when a specimen of Mecocheirus pearcei was recovered. However, just because I have not seen them does not mean they are not there since I am looking for vertebrate remains more often than not.

In my eyes, some of the most remarkable and delicate fossils are those of Genicularia vertebralis, an annelid worm of the class Polychaetia. The “fossils” are actually the casts of the burrows these worms created and are represented by calcified shells. Some are wonderfully preserved, albeit somewhat fragile and the preservation of the ornamentation never fails to delight.

Genicularia

Bivalves are well represented in the quarries and are dominated by Gryphaea dilobotes and these, although generally abundant throughout, can often be found in large dense encrustations. Some can get really big, with some recovered pieces suggesting shells over 100mm long but they are exceptional and most are around half that size with every other size and morphology in between. They are quite fragile as well and need gentle handling when a good specimen is found.

Gryphaea

Other bivalves include Pinna mitis which are often only found as imprints in newly uncovered clay. These are often mistaken for the imprints of fish fins or tails by those who are unfamiliar with them and it is easy to see why. Pinna are elongate fan-like bivalves with multiple, densely packed ribbing and, when crushed, really do look like fish fins. Another bivalve I’ve seen is Trigonia Sp. But this is likely to have been derived from the Middle Oxford Clay.

Plant fossils are not so well known from the clay and yet there is evidence for them throughout the quarries. They are all land plants that have drifted out to sea, most likely carried by rivers in flood that have eventually sunk to the sea floor. Large chunks of wood that have become carbonised can be found all over the place although once exposed to air they quickly crumble and often turn to dust. Some of us have attempted to save a few of the better preserved pieces but it takes vast amounts of consolidant to stabilise them and they need constant review otherwise they are prone to deterioration at a rapid rate.

Whole logs are sometimes uncovered but they are seldom removed, as you may remember from an earlier post. But every now and then, an odd branch or frond may fossilise well and these are extremely rare. My very first visit to Quarry 4, some years ago, revealed a freshly exposed piece of tree bark - the only example I have ever seen. It has taken a lot of maintenance to keep it intact but it is a wonderful piece and displays superb ripple-like marks in the bark.

Tree Bark

There is one other fossil worth a mention and that is that there is an abundance of fish coprolites in the clay. These are often ignored by some who do not recognise them as such and there are those who ignore them anyway but they are missing out in my opinion. The vast majority are small, only 5 to 10mm on average, pretty nondescript and are a dirty white in colour. They tend to be like this because they are largely composed of phosphate derived from digested fish bone.

However, some have quite distinct forms and the bigger ones are much more interesting since closer inspection reveals the remnants of what had been digested and passed through the gut such as small fish bones and remains of crustaceans. Rarest of all are coprolites of the marine reptiles but, every now and then, one is found and the inclusions in these are much larger and, although almost impossible to identify, are suggestive of bone and ammonite pieces, and are quite intriguing.

Coprolites displaying inclusions

Alamosaurus and the Naashoibito

2011-10-13T13:15:00.002+01:00

In the latest edition of the Journal of Vertebrate Paleontology, there was an interesting paper by Michael D’emic et al describing a titanosaurid pes from the Naashoibito member of the Kirtland Formation in New Mexico. The specimen (NMMNH P-49967) displays synapomorphies referable to a titanosauriform neosauropod and is almost certainly referable to Alamosaurus sanjuanensis, although additional remains would be needed to confirm validity.

The specimen, however, is from a very large sauropod indeed and, when limb proportions are compared and scaled up, is comparable to both Brachiosaurus altithorax and Paralititan stromeri. Alamosaurus is the only recognised Late Cretaceous titanosaur from North America but its taxanomic status has always been subject to review (eg Sullivan & Lucas 2000) but this paper reaffirms its belief that the Alamosaurus holotype is diagnostic and should be considered a valid genus.

The interesting thing for me in the paper is the referral, yet again, to the geological position of the Naashoibito Member and whether it belongs to the Ojo Alamo Formation or not. There is a consensus these days, however, regarding the age of the Naashoibito and it is now generally accepted to be Maastrichtian. The type specimen of Alamosaurus was recovered from the Ojo Alamo Sandstone which, during 1980, had been considered part of the Naashoibito Member of the Kirtland Shale (Kues et al 1980).

However, the Ojo Alamo is amongst the stratigraphically highest horizons for dinosaur remains, so high in fact that there has been occasion to suspect that a few dinosaurs survived into the Palaeocene but this has been hotly contested (Fasset et al 2002, Lucas & Sullivan 2000) and is generally not considered these days but, as these things do, rumours persist. Today, the Ojo Alamo appears to be distinct from the Naashoibito and is a particularly interesting formation in its own right because it does indeed straddle the Maastrichtian/Danian contact.

From Williamson & Weil 2008

The general consensus (it appears to me) is that the Naashoibito is part of the underlying Kirtland Formation demonstrating a Lancian fauna or, as is generally known, the "Alamosaurus fauna". It has been recognised for some time now that there have been distinct Maastrichtian faunas and this provincialism is perhaps better recognised from earlier Campanian times but it is a fact that faunal provincialism continued right through to the end of the Cretaceous.

The paleoenvironment of the Alamosaurus fauna was characterised by valleys that were situated between mountain ranges and were frequented, not only by titanosaurs, but by hadrosaurs, ceratopsians and theropods. The Hell Creek Formation, by contrast, represents a coastal plain environment that was warm, humid and wet and was dominated by ceratopsians, hadrosaurs and tyrannosaurids – but no sauropods. The Scollard and Willow Creek formations demonstrate a third environment described as a semiarid, alluvial plain and contains remains of ceratopsians, hadrosaurs, ankylosaurs and tyrannosaurs but, again, no sauropods.

It is this provincialism that has kept apart Alamosaurus and Tyrannosaurus, thus preventing a possible (and very popular) clash of these titanic animals – but maybe not for much longer. Tyrannosaurus appears to have been able to exist in a range of paleoenvironments and a specimen recovered from the North Horn Formation of Utah (Sampson 2005) was the first example of the giant carnivore apparently co-existing with Alamosaurus.

Just when Alamosaurus appeared in the Late Cretaceous is still subject to debate but it seems that titanosaurs appeared during the Campanian around 73 million years ago although their exact point of origin remains undetermined. Suggestions include a possible migration from South America to the north due to the appearance of a land bridge between the continents. This may have been due to climate change since the Western Interior Seaway was also receding at this time and this may have created the ideal conditions for the migration and establishment of a relatively localised population of sauropods. Another possible titanosauriform doorway into North America may have been via Asia but this appears to lack any substantial fossil evidence at this moment in time.

It is obvious that there are vast gaps in our knowledge regarding this fascinating stage in dinosaurian history including unanswered questions that include, amongst others, sauropod phylogeny, paleoecological implications and, of course, the geology and stratigraphy of the San Juan Basin as a whole. It is apparent that the best is still to be revealed by both the Ojo Alamo and Naashoibito and one can’t help but be intrigued by these fascinating formations

Footnote

There will be yet more detail revealed regarding the taxanomic status and paleobiogeography of Alamosaurus at this years SVP conference in November and I will report on this after the conference has finished and embargo lifted.

From Russel 1992

The above image is a poor quality scan but demonstrates the San Juan Basin quite well. This is Ojo Alamo Spring revealing the yellowish sandstonesof the Naashoibito. The Ojo Alamo Formation is exposed on the horizon in this shot.

References

D’emic, M.D., Jeffrey A. Wilson & Thomas E. Williamson (2011): A sauropod dinosaur pes from the latest Cretaceous of North America and the validity of Alamosaurus sanjuanensis (Sauropoda, Titanosauria), Journal of Vertebrate Paleontology, 31:5, 1072-1079

Fassett, J. E., R. A. Zielinski, and J. R. Budahn. 2002. Dinosaurs that did not die: evidence for Palaeocene dinosaurs in the Ojo Alamo Sandstone, San Juan Basin, New Mexico; pp. 307–336 in C. Koeberl and K. G. MacLeod (eds), Catastrophic Events and Mass Extinctions. Geological Society of America Special Paper 356.

Kues, B. S., T. Lehman, and J. K. Rigby Jr. 1980. The teeth of Alamosaurus sanjuanensis, a Late Cretaceous sauropod. Journal of Paleontology 54:864–868.

Lucas, S. G., and R. M. Sullivan. 2000. The sauropod dinosaur Alamosaurus from the Upper Cretaceous of the San Juan Basin, New Mexico. New Mexico Museum of Natural History and Science Bulletin 17:147–156.

Russel, D.A. 1992. The “Modern” Cretaceous in An Odyssey in Time: The Dinosaurs of North America. University of Toronto Press in association with the National Museum of Natural Sciences. ISBN 0-08020-7718-8.

Sampson, S. D., and M. A. Loewen. 2005. Tyrannosaurus rex from the Upper Cretaceous (Maastrichtian) North Horn Formation of Utah: biogeographic and paleoecologic implications. Journal of Vertebrate Paleontology 25:469–472.

Sullivan, R. M., and S. G. Lucas. 2000. Alamosaurus (Dinosauria: Sauropoda) from the late Campanian of New Mexico and its significance. Journal of Vertebrate Paleontology 20:400–403.

Amazingly Preserved New Theropod Announced

2011-10-12T22:05:00.001+01:00

Meet the new guy on the block. This has broken out all over the paleoworld tonight and is causing quite a stir – and rightly so. Oliver Rauhut and his fellow workers from the Bavarian State Museum for Palaeontology and Geology made the announcement earlier today.

Found in Upper Jurassic sediments, around 150 million years old, the skeleton is incredibly 98% complete representing a juvenile theropod and is 72cm long. This small animal represents the most complete theropod ever found in Europe and one of the most complete in the world. The animal will be officially announced on October 27^th in Munich and as yet has no official name or description but as you can see from this image, it is a spectacular specimen.

Fellow blogger Andrea Cau has initially described it as possibly a “compsognathid-grade tetanuran” (with a proviso!) and very Juravenator-like whilst Tom Holtz has already mentioned that the animal has “.....some pretty big implications.” Expect the wires to be ablaze for days to come regarding this little guy!

Pterosaur Sneak Preview

2011-10-06T15:23:00.002+01:00

Just a brief post this week because of work commitments and features a sneak preview of one of the most wonderfully preserved pterosaur fossils I’ve ever seen. I’ll be featuring more of this spectacular specimen in the near future - it really does have to be seen to be believed. I will be back to normal posting next week.

Watchet & Kilve

2011-09-29T12:28:00.000+01:00

I couldn’t make SVPCA in Lyme Regis this year as I was already committed to a family holiday at the same time. It never fails to amaze me how often conferences and holidays clash but that’s life and I was determined to enjoy myself anyway. As it turned out I too was in the south west, in Somerset, and while I was there I decided to check out some of the well known fossil localities in the area.

The most famous amongst these is probably Watchet and this will be a very familiar locality to marine reptile fossil hunters in the UK. This section of the coast is also of great interest to geologists and there are excellent examples of faulting and unconformities. The cliffs in some parts of this coastline are also under constant attack from the sea and erode readily but at different rates. For example, the Lias cliffs erode quite rapidly and this is naturally of concern to those living here and some preventative measures have been taken to protect, for example, the railway line that runs parallel to the shore.

The red Keuper marl beds of the Triassic can be observed here and these are faulted against the green marls. But it is the mudstone rocks of the Lower Lias (Hettangian) that is of most interest and these contain ammonites and numerous crinoid fragments. As always though, it is the various remains of ichthyosaurs and plesiosaurs that have the most appeal and, just like the other coastal exposures, they have been heavily plundered and the venue continues to be scoured by collectors.

Under normal conditions, there is very little to be found these days until there is a storm and/or new cliff falls and then collecting can be productive. The strata dips seaward and where the sea platforms slope up and face the inland side, they are very efficient at collecting nodules, cobbles and shingle and when these are scoured in the spring or autumn tides, they can also reveal reptile bones.

Watchet is a lovely place to visit and the town itself is quiet and the small esplanade is attractive. Take time to have a look at the Geological Wall on the station platform and pay a visit to the tiny museum as well. The museum has a small collection of local fossils and indeed has a small, virtually complete ichthyosaur although it appears, to me, to be a poor example. Never the less it is still a nice little museum and the local history of Watchet is equally fascinating.

As you head eastwards from Watchet, and not too far away, is Kilve and this is another classic locality. The rocks here are very similar to Watchet and are of similar age with both the cliffs and foreshore demonstrating excellent exposures of the Lower Jurassic Blue Lias and these include sequences of black shales, marls and limestone.

Ammonites are relatively common in the shales, represented by Psiloceras planorbis, and there are also trace fossils to be seen but these are almost impossible to extract and are best left alone. But ammonites can be recovered and these are best preserved when they are found in nodules but the trick these days is to find one!

The strata at Kilve also dips seaward and there are a multitude of sloping ramparts on the shore that gathers up debris and nodules just like Watchet. It was said of Kilve that ichthyosaur vertebrae were extremely common, so common in fact that you could almost guarantee finding a couple but this is sadly not the case today. Bones of both ichthyosaurs and plesiosaurs can be found, sometimes matrix free, but usually in nodules, just like the ammonites. Again, fresh cliff falls, storms and scouring tides are needed to expose any new material.

While I was at Kilve, there were many people turning up with hammers and kit and they were all fossil hunting. As some left, others arrived and the same areas were continually being scoured. Again this highlights the pressure that the coastal venues are under and it is no surprise that so little is found these days and I think it is rather sad that these classic localities are having their cupboards continually stripped bare.

Having said that, Kilve is a beautiful place to visit and the geology is equally fascinating and, if you are in the area, make sure you take the time to have a look. There is parking available (pay and display), toilet facilities and a nice area for a picnic. Recommended.

The end of a storm over Watchet

Tyrannosaurid Forelimbs - Why, What or Something Else?

2011-09-22T20:59:00.000+01:00

The small arms of Tyrannosaurus rex have provoked discussion and reaction since the animal was first discovered in 1902 (not including the 1900 specimen BMNH R7994 “Dynamosaurus imperiosus”). It is a fact, however, that very few examples of the forelimb were recovered until MOR 555 was found south of Fort Peck Lake in 1988 where a nearly complete left arm and manus were excavated. And because of the increase in specimens found since the 1990’s, there has been more material made available which has enabled further study.

The original theory, proposed by Henry Fairfield Osborn in 1906, was that they were an adaption to assist in the act of copulation although he only proposed this after accepting that the relatively small humerus found with the specimen actually belonged to the animal. Other theories have suggested that the arms were used to help brace the animal and push it up as it rose to stand up (Newman 1970) or that, indeed, these limbs were actually of no consequence whatsoever and were degenerate and were actually in the process of being lost.

For me, one of the real issues with trying to demonstrate theories about the forelimbs of Tyrannosaurus is that we don’t think laterally enough. First of all, reduced forelimb size is almost universal throughout Theropoda. Since dinosaurs first evolved in the Triassic, theropods were bipedal, largely carnivorous and the forelimbs were less than two thirds the length of the hindlimb (Holtz & Osmolska 2004). There were general reductions in the length of some digits and metacarpals and the manus generally ended with sharp recurved claws.

Bipedality obviously demanded a reduction in the size of the forelimb – for me that is a given. However, tyrannosaurids have taken this reduction to an extreme and here is another point to bear in mind. If we look at the clade Tyrannosauridae as a whole, then we can see that all tyrannosaurids have greatly reduced forelimbs so we are not looking to determine the use of these forelimbs only in Tyrannosaurus – and that’s important.

With odd exceptions then (Deinocheirus being the most obvious), theropods all have short forelimbs to various degrees. Early coelophysoids had fairly useful forelimbs as did both basal and derived tetanurans whilst ornithomimosaurs had extremely beneficial elongate forelimbs. At the other extreme are the abelisaurids and Carnotaurus displays the smallest forelimbs possible for an animal approaching 25 feet in length – and seemingly useless (but see Ruiz et al 2011). They make tyrannosaur forelimbs appear positively huge. Also of significance is that no theropod could reach its mouth with its manus.

Did theropod forelimbs help with balancing, turning and agility? Possibly. Smaller and lighter forelimbs would certainly help the animal turn and it has also been suggested that theropods held their arms backward and against their bodies in situations where speed and agility was required (Carrier et al 2001). One thing seems certain and that is that reduced sized arms would certainly not help any theropod if it tripped whilst walking or running and this was one of the principle objections against large theropods being able to run fast. And yet there are multiple examples of theropods with healed fractures on bones such as the ribs that are indicative of this very scenario.

So with this overall view of theropod arms, it can be seen that tyrannosaur arms do follow a general pattern but they are different in other ways. Significantly, there appeared to be no further reduction in limb size once it had been established in Tyrannosauridae since the ratio between forelimb and hindlimb was fairly constant from the Campanian to the end of the Maastrichtian.

The forelimbs of tyrannosaurids were strong, agile and capable of coping with powerful stress forces but they had a limited range of motion. The two claws faced in opposing directions and were ideally designed to act like barbed fishing hooks and would not have easily been dislodged from the flesh of a prey animal. The biceps were extremely large and were the driving force behind the forelimbs ability to bear weight – in the case of Tyrannosaurus, that is estimated to exceed 400 pounds.

As if to provide evidence that the forelimbs were subjected to substantial forces, the bones in tyrannosaur arms are often found with pathologies – that is they have been fractured or broken and have healed up accordingly. This demonstrates that tyrannosaurs could cope without the use of an arm or two for a period of time – certainly long enough for the bones to heal. Some think that this is actual evidence that the arms were not up to the job and that they were poorly adapted but then why would they be subjected to such pressures?

Perhaps the forelimbs were much more useful to juveniles and allometric studies of limb proportions in tyrannosaurs suggests that the forelimbs were relatively longer in juveniles and thus of more functional consequence, especially if their dietary requirements were different when juvenile. Recent study of the well publicised Tarbosaurus juvenile (Tsuihiji et al 2011) seems to complement this observation by uncovering other allometric implications for different feeding strategies in the skull.

So where does this all this lead? What conclusions can be made about the use of these forelimbs in tyrannosaurids? Well actually very little. For me, the belief that they were vestigial organs and gradually being lost does not quite ring true since, if that was the case, then why were they still so powerful? Nature tends not to bestow natural power for nothing and certainly not more power than the animal needs.

Other suggestions include nest or bed scraping (unlikely and surely they would use the foot?) and egg rotation (just unlikely). Getting back to the more popular and realistic theories, the powerfully constructed forelimb has recently been determined to be a not insignificant aid in predation and would have helped the tyrannosaur keep hold of its prey (Lipkin & Carpenter 2008). They may have also helped the animal manoeuvre the carcass as the animal fed.

Strangely, and going back to the very first theory put forward by Osborn, procreation has also been suggested in as much that the forelimbs helped the male cling onto the female during copulation, and perhaps there is something in this. This idea has some merit since tyrannosaurs obviously displayed at least some intraspecific interaction as demonstrated by the well documented face biting injuries (Tanke & Currie 1998).

For me, it also seems a possibility that perhaps the forelimbs may have actually been used for courtship purposes. Because it is a behavioural implication, it is completely untestable, but perhaps they were subtle signalling devices demonstrating a male’s intention to mate and the females signal that she was receptive. If courtship was a body rubbing issue, perhaps the forelimbs were also used to “stroke” and groom each other in all the right places.

This appears to be a reasonable suggestion since you would imagine that animals as powerful and as dangerous as tyrannosaurs would need some form of mating ritual so that they avoided hurting each other unnecessarily during the mating season. In the end, this continual speculation about the purpose of tyrannosaur forelimbs will go on but you always hope that the next fossil found may provide the answer to this fascinating and enduring question.

References

Carrier, D.R., Rebecca M. Walter and David V. Lee (2001). Influence of rotational inertia on turning performance of theropod dinosaurs: clues from humans with increased rotational inertia. Journal of Experimental Biology (Company of Biologists) 204 (22): 3917–3926. PMID 11807109.

Holtz, T.R., Jr. & H. Osmólska. 2004. Saurischia. Pp. 21-46, in D.B. Weishampel, P. Dodson and H. Osmólska (eds.), The Dinosauria. Second Edition. University of California Press.

Lipkin, C., and Carpenter, Kenneth (2008). Looking again at the forelimb of Tyrannosaurus rex. In Carpenter, Kenneth; and Larson, Peter E. (editors). Tyrannosaurus rex, the Tyrant King (Life of the Past). Bloomington: Indiana University Press. pp. 167–190. ISBN 0-253-35087-5

Newman, BH (1970). Stance and gait in the flesh-eating Tyrannosaurus. Biological Journal of the Linnean Society 2: 119–123.

Osborn, H.F., Brown, Barnum (1906). Tyrannosaurus, Upper Cretaceous carnivorous dinosaur. Bulletin of the AMNH (New York City: American Museum of Natural History) 22 (16): 281–296.

Ruiz, J., Angélica Torices, Humberto Serrano and Valle López (2011) The hand structure of Carnotaurus sastrei (Theropoda, Abelisauridae): implications for hand diversity and evolution in abelisaurids. Palaeontology 54 (5) Article first published online: 19 Sep 2011 DOI: 10.1111/j.1475-4983.2011.01091.

Tanke, D.H., and Currie, Philip J. (1998). Head-biting behavior in theropod dinosaurs: paleopathological evidence. Gaia (15): 167–184. ISSN 0871-5424.

Tsuihiji, T., M. Watabe, K. Tsogtbaatar, T. Tsubamoto, R. Barsbold, S. Suzuki, A. H. Lee, R. C. Ridgely, Y. Kawahara, and L. M. Witmer 2011. Cranial osteology of a juvenile specimen of Tarbosaurus bataar from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia. Journal of Vertebrate Paleontology. 31(3).

Wednesday Night is Dino Night!

2011-09-21T18:13:00.000+01:00

As Stu Pond has already pointed out over at Paleo Illustrata, the programme How to Build a Dinosaur debuts at 9 o'clock GMT on BBC4 tonight and features amongst others Darren Naish and, I seem to recall, that John Hutchinson makes an appearance as well. The programme looks at how a dinosaur skeleton is put back together and investigates how details such as muscle, posture and skin colour are determined.

Straight after that at, 10 o'clock on the same channel, comes Extinct: A Horizon Guide to Dinosaurs and looks at how our scientific knowledge of dinosaurs has evolved since the 1970's. I didn't even know this one was coming up so have don't have any details as such but, as the Horizon team is involved, I hope that the programme will prove interesting.

And before both these programmes air, we have the second part of Planet Dinosaur on BBC1 at 8.30, this time focusing on feathered dinosaurs. It will be interesting to compare the Gigantoraptor restoration with the same animal in Dinosaur Revolution. Enjoy!

Fossil Teeth Reveal So Much Data

2011-09-15T13:23:00.000+01:00

I’ve blogged about fossil teeth before and, more recently, referred to Eagle et als paper (2011) which demonstrated how dinosaur body temperature could be determined by analysis of tooth enamel. Teeth are able to provide an amazing amount of data and some of it is often surprising.

The best thing about teeth is that they fossilise quite readily. They are tough and reliably tolerant of distortion and they can be found in such pristine condition that it looks like they may have been shed only yesterday. And they are relatively commonplace in many localities, even when skeletal remains are rare. Chief amongst the providers of teeth are vertebrate microsites and these provide a valuable window into the make up of a vertebrate palaeocommunity with not only dinosaurs but also fish, amphibians, other reptiles, mammals and birds sometimes all represented.

Identifying dinosaur species at family, generic and species level has represented an ongoing challenge for several authors over the years. Teeth, even those that are stunningly preserved, can often only be diagnosed to family level since, beyond this point, it is common for taxon specific teeth to be almost identical, thus harder to diagnose. Those teeth that are naturally worn, broken and weathered are even harder to assign.

So there is always an element of error in identifying scattered isolated teeth unless they are associated with skeletal material and it is very likely that some isolated teeth probably represent new taxa yet to be discovered. And yet today there is more and more detail being extrapolated from fossil teeth than ever before.

The aforementioned tooth enamel is now also being used as a tool to aid identification. Hwang (2010) has been examining the microstructure of tooth enamel using scanning electron microscopy and the details revealed have proven illuminating. Of particular interest is the fact that teeth, despite looking morphologically similar, can be differentiated because of the make up of the enamel. This is really useful with groups such as hadrosaurs, ankylosaurs and tyrannosaurs.

However, although this technique enables teeth to be identified more readily, it still is not always possible to provide diagnosis at the generic or species level. But even here, there has been a modicum of success and a few specimens have indeed been identified to the genus level. This research is yet another tool helping to identify isolated teeth and will be especially useful in identifying those that are too damaged or worn and unidentifiable.

Theropod teeth are always impressive to look at and as such are intensely researched and the chief interest around their morphology usually focuses on their serrations. The most obvious analogy that everybody is familiar with, especially in the popular media, is that serrations on teeth made them akin to a steak knife of today and aided the animal in cutting through flesh and slicing and dicing meat. But things are seldom as simple as this.

Serrations, or denticles to give them their correct term, have been described as helping the tooth penetrate flesh and bone but with less force than would be required with a tooth that had none (Abler 1992). Generally speaking, theropod teeth are more densely serrated distally than they are mesially, troodontid teeth not withstanding. But teeth need to work in conjunction with a number of other factors to make them truly efficient.

D’Amore (2009) conducted experiments that demonstrated that the curvature of teeth increased distally in the dentary which made for a very efficient jaw mechanism. Its simple mechanics when you think about it in as much as the tooth that is closest to the hinge will pass through the greatest amount of rotation, thus needing to be more recurved so that it penetrates the substrate efficiently whilst those at the front of the dentary tend to be straighter because they do not go through such an acute angle (see below).

From D'Amore 2009

Tooth serrations are remarkably efficient since so many taxa have developed them, both extinct and extant. Experiments using finite element analysis (FEA) have also been utilised to determine their functionality and how they may have evolved, not only in dinosaurs, but also in sharks and mosasaurs. Various elements have to be taken into consideration when utilising FEA in this form of study such as variation in denticle composition, the overall gross morphology of the teeth and how the distribution of pressure and different stress levels affects these different morphologies.

Miriam Reichel of the University of Alberta has been performing this research over the last few years as part of her PhD project and has found that tooth function dictates how teeth are serrated and affects their physical properties. To emphasise the efficiency of serrations, all teeth subjected to the pressure of estimated bite forces performed admirably with very little stress displayed.

So it can be seen that teeth, even today, are still yielding a wealth of information and will, no doubt continue to do so. The fact that there are so many teeth to work with is obviously a contributing factor. Theropods replaced their teeth continuously throughout their lives and, asides from the previously mentioned microsites, are found in association with skeletal remains, often scattered throughout the carcass and the immediate surroundings.

Strangely though, when theropod skulls and jaws are recovered, they seldom have vacant tooth sockets displayed and, when this is compared with the amount of shed teeth that are found, suggests that tooth replacement in theropods was indeed rapid. And, luckily for us, this provides a wealth of fossil teeth that will continue to satisfy our continual thirst for knowledge in the foreseeable future.

References

Abler, W. L. 1992 The serrated teeth of tyrannosaurid dinosaurs, and biting structures in other animals. Paleobiology 18, 161–183.

D'Amore DC. 2009. A functional explanation for denticulation in theropod dinosaur teeth. Anatomical Record 292: 1297–1314.

Eagle, R.A., Thomas Tütken, Taylor S. Martin, Aradhna K. Tripati, Henry C. Fricke, Melissa Connely, Richard L. Cifelli, John M. Eiler. Dinosaur Body Temperatures Determined from Isotopic (13C-18O) Ordering in Fossil Biominerals. Science, 2011; DOI: 10.1126/science.1206196

Hwang, S.H., (2010) The evolution of dinosaur tooth enamel microstructure. Biological Reviews Volume 86, Issue 1, pages 183–216, February 2011 Online publication date: 1-May-2010.

Planet Dinosaur Arrives

2011-09-11T19:36:00.000+01:00

A Cau-inspired Spinosaurus head.

It cannot have escaped your attention that the two biggest dinosaur documentary series of the year are both airing in September. The first two parts of Dinosaur Revolution have aired in the US to the usual mixed reaction but my general feeling (at the moment) is that the positive reviews are edging it over the negative side.

I have seen the first two episodes of Dinosaur Revolution and will save the review for a later post when the series is complete. Suffice to say that I too have mixed feelings so far. I wasn’t too impressed with the first part but did enjoy the second part despite the usual technicalities and obvious poetic licence.

And now comes Planet Dinosaur from the BBC, airing in the UK for the first time this Wednesday at 8.30 on BBC1. This is now ten years after the original Walking with Dinosaurs (WWD) hit our screens and is seen as the natural successor to that series since so much has happened in the world of dinosaur palaeontology during that time that the BBC deemed it was time for a new series and are hoping that it will be as successful as its predecessor.

This time the narrator is John Hurt and the series is in six 30 minute instalments and there are other differences as well. WWD placed CGI dinosaurs in locations that were filmed all over the world, and very effective it was too, but this series recreates, in its entirety, both the prehistoric landscapes and animals that lived in them. The primary thinking behind this was that it gave the film makers much more freedom and the camera could be placed anywhere they wanted and this, they hope, will make it seem much more real to the watching audience.

Because CGI has improved so much over the last decade, the producers were keen to exploit the plethora of new discoveries for the series but the older established animals are also well represented. For example, the first episode entitled Lost World, features both Spinosaurus and Carcharodontosaurus but, alas, there is also a big battle scene between the two with more than a hint of Jurassic Fight Club.

The producers deny this and say that despite the inevitable dinosaurian battles, there will be plenty of cutting edge science including how forensic science of fossils is providing lots of new data and how computer analysis of fossils is doing the same.

To be fair, we will have to wait and reserve judgement until we see how the series pans out but, worryingly, one of the producers, Andrew Cohen, has stated (and I quote) “Planet Dinosaur is more like an action film than a natural history film”. We can only hope that this a little tongue-in-cheek and hope that there is, indeed, some science in there. That isn’t too much to ask is it?

Hadrosaurs - Underrated Yet Spectacular (Part 2)

2011-09-07T14:53:00.001+01:00

Back to hadrosaurs then and a closer look at some more interesting points of note about them – especially the lambeosaurines. As mentioned previously, hadrosaurs are split into two sub-families – the Hadrosaurinae and Lambeosaurinae. Hadrosaurines are usually diagnosed by a laterally broad edged premaxillary process that defines the classic “duck bill”; the nasal arches are not indented and some of the more derived taxa have crests that are solid.

Lambeosaurines are diagnosed by vertebrae that have longer neural processes than hadrosaurines; the ischium terminates distally with a flared process and the large nasal cavity often forms crests that are both spectacular and hollow. It is these crests that were once associated with the theory that hadrosaurs were semi-aquatic.

Semi-aquatic dinosaurs have been back in the news again recently (Ford 2010) and hadrosaurids were once considered amphibious, a theory first considered by Leidy way back in 1858 and supported by Cope in 1883. Indeed, growing up with dinosaurs, I was very familiar with hadrosaurs portrayed as aquatic animals and there was hardly any picture of them that didn’t show them as swimming and wading in the Late Cretaceous swamps or fleeing into the water to escape the jaws of an approaching tyrannosaur.

To be fair, at the time, the interpretation of the evidence seemed reasonable. The beak of hadrosaurs was thought to be weak and only suitable for cropping soft vegetation such as that which is found growing in or next to water. The tail, because it was wide, scull-like and obviously strong was imagined to be a powerful propeller which enabled the hadrosaurs to swim very effectively and then, when the famous “Trachodon” mummy was found in 1908, not only were significant amounts of skin preserved, but skin found preserved on the manus appeared to represent webbing situated between the digits, thus appearing to form a kind of flipper. This interpretation of hadrosaurs as semi-aquatic dinosaurs remained intact for many a year.

Since those early theories, we now know that hadrosaurs were highly developed terrestrial bipeds able to alternate between both quadrapedal and bipedal locomotion, depending on what the situation dictated at the time. The tail, as described in the previous post, was consolidated along the dorsal and caudal vertebrae by ossified tendons which stiffened the tail considerably and, despite still being immensely powerful, was not suitable for aquatic propulsion.

It also turns out that that horny beak of hadrosaurs was anything but weak and was a highly efficient cropping tool that comfortably cut through plant material ready for transferral to the dental batteries. A reassessment of the manus also reveals unguals that were obviously performing the same function as hooves, seen in a multitude of extant animals today – an exclusively terrestrial adaption.

Finally, the webbing on the dinosaur mummy that seemed to so support a semi-aquatic lifestyle proved to be a bit of a red herring since closer study revealed the webbing to be highly constricted between the digits and they could not be spread far apart enough to form a sculling paddle anyway. Other taphonomic processes had also distorted the preservation process causing interpretation of some skin remnants to be incorrect.

Despite this, there are still some voices suggesting that perhaps we should not totally discount the possibility of semi-aquatic hadrosaurs. It seems likely that they may indeed have been partial to the odd paddle especially since they seem to have spent so much of their time in both freshwater and coastal habitats.

Interestingly, it was thought that the crests of hadrosaurs, and lambeosaurines in particular, were also part of the adaption to an aquatic life. Because many of the crests were hollow, it was deemed that they could be used like a snorkel or, at the very least, act as an oxygen tank to enable the animal to dive under water. However, the nostrils of hadrosaurs are located anteriorly on the skull and positioned low and are certainly of no use to a snorkelling animal. And as for acting as an oxygen reservoir, well the amount of air that could be retained in the crests was so small as of to be no help to an animal weighing perhaps three and a half tons with big lungs. No, there are better explanations to describe the functionality of crests in hadrosaurs.

One theory is that they were a cooling mechanism to help dispel excess heat around the brain. Respiratory turbinates in dinosaurs have been considered intensely over the last few years and whether they were, indeed, part of dinosaur physiology. It is possible that the crests created more surface area within the nasal network, thus being able to dispel a greater amount of heat because the amount of blood that was being cooled by air during breathing would be greater.

The problem with this theory is that it is awfully hard to find physical evidence for respiratory turbinates on fossil bone although a recent specimen seems to suggest that there may have been (but for the life of me I cannot find the reference). Hadrosaurines may also have been able to utilise the same utility since they also have large nasal cavities.

Another suggestion was that the crests enhanced the sense of smell, again due to the greater surface area of the crest that was infused with olfactory epithelium. However, further research and comparisons with the nasal chambers of extant reptiles suggest this was most unlikely and that the crests played no part in olfactory sensory ability (Evans 2006).

So it seems likely that the crests had other functions and now appears likely that they were an essential part of the complex social behaviour in hadrosaurs. The variation in size and shape suggests that some crests are probably sexually dimorphic and specimens of Lambeosaurus, Corythosaurus and others have been identified as probably being male or female (Evans 2006). It is also likely that the crests were highly coloured which may have helped to identify sexually mature animals and also to ward off potential rivals when competing for mates or territory.

Of course, low frequency sound, when amplified by a suitable resonating chamber, has the ability to travel long distances and the hollow crests of hadrosaurs were well suited to the task. Some very impressive experiments with the skull of Parasaurolophus have produced some startling, almost imperceptive sounds that would have undoubtedly aided intraspecific communication (Diegert 1998).

Image courtesy of Aquaimages

Although hadrosaurines generally lacked raised cranial ornamentation, they, never the less, may have possessed a resonating sac that was located in the deep depression that surrounded the external nares. This could also have been brightly coloured and the combination of sound and inflated air sac would have made for an impressive display – something similar to the frigatebird of today.

So it can be seen that hadrosaurs provide the best overall window into the complex social structure and interaction of any group of dinosaurs. Nesting sites, the amazing array of crests, the production of sounds and the probable use of colour all demonstrate that these amazing animals were complex animals with a surprisingly intricate infrastructure culminating in the remarkable nursery care of the young hatchlings. Cows of the Cretaceous? Don’t believe a word of it – hadrosaurs are uber-cool.

References

Cope, E.D. 1883. On the characters of the skull in the Hadrosauridae. Proceedings of the Academy of Natural Sciences of Philadelphia 35:97–107.

Diegert, Carl F.; and Williamson, Thomas E. (1998). A digital acoustic model of the lambeosaurine hadrosaur Parasaurolophus tubicen. Journal of Vertebrate Paleontology 18 (3, Suppl.): 38A.

Evans, David C. (2006). Nasal cavity homologies and cranial crest function in lambeosaurine dinosaurs. Paleobiology 32 (1): 109–125.

Ford, Tracy L.; and Martin, Larry D. (2010). A semi-aquatic life habit for Psittacosaurus. In Ryan, Michael J.; Chinnery-Allgeier, Brenda J.; and Eberth, David A. (editors.). New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. Bloomington and Indianapolis: Indiana University Press. pp. 328–339. ISBN 978-0-253-35358-0.

Leidy, J. 1858. Hadrosaurus foulkii, a new saurian from the Cretaceous of New Jersey, related to Iguanodon. Proceedings of the Academy of Natural Sciences of Philadelphia 10: 213–218.

Wren's Nest Under Threat

2011-08-31T13:40:00.000+01:00

You will forgive me if I deviate from the usual bill of fare for this blog but, every now and then, something crops up that you have to make people aware of and do your bit – and now is one of those occasions.

The Wren’s Nest National Nature Reserve is a renowned geological site of international importance. For those of you unfamiliar with locality, the Wren’s Nest is located in Dudley, near Birmingham in the UK and has significant historical value to the disciplines of both geology and palaeontology.

The Wren’s Nest exposes rocks of Silurian age – about 420 million years old and represents coral reefs within a tropical sea with a diverse marine community that includes crinoids, brachiopods, trilobites and many other animals. Their fossils are found in the limestone exposures and are often well preserved.

Image courtesy of Ashley Dace

The importance of the site cannot be denied. More than 700 different types of fossil have been recovered, of which 186 were first found and described here and, even today, there are 86 taxa which are totally unique to the Wren’s Nest.

One of the pioneers of geology, Sir Roderick Murchison, was a frequent visitor during the 1830’s and his landmark work, The Silurian System, was published in 1839 and featured extensive descriptions and illustrations of the fossils recovered from the site.

The Wren’s Nest became the UK’s first geologic National Nature Reserve back in 1956 because of its unique geological and palaeontological features. Further protection arrived in the form of the venue being declared a Scheduled Ancient Monument in 2004 and the future of the site seemed assured.

But, as incredible as it sounds, there are now plans to build a new housing estate actually in the reserve. There are to be eighty houses in total and will be built on the exposures of the Coalbrookdale Formation which, even today, is comparatively little known or researched and underlies the limestone strata.

I do not intend to go into the politics and drama of the issue but suffice to say that money is the root cause of the problem and the fact that these plans have been put into motion for more than twelve months now without anybody being made aware is significant. Only recently have plans been put into action to mount a serious campaign of opposition.

Amazingly, this housing project has been instigated with seemingly blind ignorance of further plans to develop the Wren’s Nest as part of the Strata Project – a geotourist scheme that has gained both local and national support. The project links other geological features such as the Steps Cavern, the limestone mines and the canal tunnel that links the Nest with Dudley Castle.

A modern research centre with laboratories, a visitor centre, restaurant and even a small hotel are included in the plans that would accommodate some of the 50,000 forecasted visitors per year. It has been suggested that perhaps those planning the housing estate were unaware of the Strata Project but does anybody seriously believe that?

Only recently, top geologists from the International Subcommittee on Silurian Stratigraphy visited the Wren’s Nest and confirmed the international significance of the venue and simply described it as “…the best.”

You can help in trying to overturn this ludicrous decision by voicing your opposition to the housing scheme by doing one of the following:

Send your written objection to;

The Directorate of the Urban Environment,
Planning Services,
3, St. James’s Road
Dudley,
West Midlands
DY1 1HZ

Alternatively you can email your objection to:
development.control@dudley.gov.uk

Please quote Re: Planning Application Number: P11/0652 in all correspondence

The supporters of the Wren’s Nest will be grateful for your help and a special word of thanks to geologist Chris Darmon for bringing this to our attention.

Prep News 2

2011-08-24T14:47:00.000+01:00

Some of you may be familiar with the fact that we have some new plesiosaur material that we are currently preparing and looking at. The material was found in association in the Oxford Clay representing what appears to be a juvenile animal from an as yet unspecified taxon.

The animal is represented by multiple elements including one virtually complete forelimb, both femora and ribs. There are cervical, dorsal and caudal vertebrae represented but not many with processes and other large unidentified elements which are probably attributable to the pelvic or shoulder girdle. Some disassociated digits and other elements complete the recovered bones.

Unfortunately no skull material was recovered and we could not find a single tooth, which was disappointing. Cryptoclidus eurymerus is the most common plesiosaur recovered from this formation but there are subtle morphological differences in some bones which suggest this animal is something else. It is similar, however, to C. richardsoni and this is a very rare taxa indeed which may make this specimen quite important.

It s almost certainly not Muraenosaurus since that appears to be a much more robust animal. So the animal remains indeterminate at the moment and although I am erring on the side that it is possibly C. richardsoni, there is an outside chance that it may be a new taxon and that would be really exciting. We hope to get back to the site at some point and see if we can possibly locate any skull material and anything else that may help to identify the animal. The fact that the humerus is considerably larger than the femora is diagnostic of cryptoclidid plesiosaurs.

The material appears well preserved and heavily mineralised but it all has a proportion of matrix adhering to the surface in varying degrees of thickness. Some of it is merely compacted clay that is easily removed but other matrix is encrusted by calcite with remnants of both shell and belemnite embedded within and this has compacted and solidified to form a crust that is almost flint-like and is much tougher to remove.

Removal of this material is exacerbated by the fact that it almost blends into the bone and it is extremely difficult to take it away cleanly without damaging the fossil. The bulk of this material is removed mechanically but the remainder has to be removed very delicately, almost grain by grain to prevent damage and this is very much a time consuming process. The last specks are gradually eased out with needles but even at this stage they are extremely hard to remove and patience is paramount.

However, having said all that, some of the bone preservation is outstanding and this humerus is as good an example as any I’ve ever seen. This form of preservation is thought to be attributable to the fact that the Oxford clay sea was shallow and the organic material that the animals were buried in was exceptionally rich and fissile and virtually sealed in the fossils, thus enhancing preservation.

Unfortunately, many vertebrate remains are contained within calcite concretions and these are often well preserved but they are almost impossible to remove from the concretion without damaging the specimens. The plesiosaur discussed here also had a concretion in situ which had split and revealed a series of vertebrae running through it. Despite our best efforts, the concretion was so heavy that we were unable to extract it without mechanical help.

However, before extraction could be arranged, the site was covered over with spoil and the nodule seems to have disappeared but we are hopeful that it will eventually be relocated and we are optimistic the site will “reappear” after more spoil movement and, of course, more natural weathering and erosion.

After the humerus is finished being prepared, the radius and ulna are next up for preparation and these will clean up much quicker since they are much smaller elements to work on and do not appear to be too heavily encrusted with matrix. I’ll publish updates as we go along eventually unveiling the forelimb in its entirety once all the associated paddle elements are finished and, of course, any other news on the identity of the animal as we get it.

Footnote

We have recently been informed that the quarry has undergone extensive remodelling recently and that the layout has changed considerably which unfortunately lessens the chance of finding any more remains of this animal. This is regrettable but, until we are able to visit the site again, it is impossible to predict if we will be able to find any more of our plesiosaur.

Told You So.........

2011-08-21T21:14:00.001+01:00

I recently blogged about the possibility of setting up some form of judicial framework for the UK’s dwindling fossil resources, something similar to the Paleontological Resources Preservation Act in the USA. The post met with mixed reaction, both here on the blog and also via personal communication. It has been very much a positive episode for me and appears to have at least made some people think and discuss the issue.

However, at the risk of saying “I told you so”, I recently received some correspondence which again bears out my belief that something will need to be done. Fossil hunter extraordinaire and all round top man Cliff Nicklin ( a Quarry 4 & 5 colleague) recently took a family vacation on the south coast near Lyme Regis and Charmouth and, of course, not only did he spend some quality time relaxing, but also did a little fossil hunting – well you would wouldn’t you? But here is an excerpt from his recent correspondence:

“It is becoming difficult to find anything, speaking to collectors, one has not been out for three months and another six months, and they are now waiting for the usual autumn/winter storms and, of course, land slides. Collecting has become an issue, as I lay on the beach (wife was with me), I noticed everyone walking past had a hammer.

I spoke to several party leaders regarding fossil trips and business is good at £5 per go, so we know why pickings are down………..”

So despite the fact that the Jurassic Coast is a UNESCO world heritage site and despite the recently launched self-imposed code of practice and everything that it represents, I suggest that my protestation that legal protection for the UK’s fossil resources is needed at some point in the future is wrong. It is needed NOW!

Hadrosaurs - Underrated Yet Spectacular (Part 1)

2011-08-17T13:05:00.001+01:00

The International Hadrosaur Symposium takes place next month at the Royal Tyrrell Museum of Palaeontology in Alberta and is an eagerly anticipated event. It’s a busy time for the conference circus with the SVPCA in Lyme Regis running from the 12th to the 17th of September, the Hadrosaur Symposium on the 22nd to 23rd and, of course, the 71st SVP meeting is in LA from November 2nd to 5th.

There is going to be so much material and data floating around from these conferences that there will be no shortage of discussion, hotly contested debates and surprises for the palaeoworld to digest for the weeks and months that follow. The early word from SVPCA is that it will be an excellent event this year and SVP is always full of superb material but, I have to confess, that the Hadrosaur Symposium is the one I’m looking forward to more than most.

Hadrosaurs are fascinating dinosaurs. For me, they are some of the most interesting and underrated dinosaurs that have ever evolved. So they didn’t have sharp teeth, spikes or horns but, in the case of lambeosaurines, they have an amazing array of crests, grow extremely large and are extremely well represented in the fossil record with some species represented by a full ontogenetic life history from egg to adult.

Hadrosaurs can be defined by a number of unique traits and are split into two sub-families known as the Hadrosaurinae and Lambeosaurinae. For example, both groups have lost the first digit of the manus, the antitrochanter on the ilia is pronounced and robust for attachment of large muscle and the skulls display a suite of specialist characteristics.

Hadrosaurids have a worldwide distribution thus emphasising their spectacular success as a group. They are also recovered from various formations that demonstrate their adaptability to survive in different environments. These include, but are not restricted to, delta and flood plains and both lower and upper coastal plains.

In size, hadrosaurs varied enormously but the biggest such as Shantungosaurus were huge animals and were the size of the largest tyrannosaurids. Other recently recovered hadrosaurs from China are equally massive. Take a look here at Dave Hone’s recent images of Shantungosaurus – awesome animal, very impressive. Some recent work by Cooper (2008) again demonstrates that hadrosaurs grew extremely fast – at mammalian-like endothermic rates and attained adult size within 8 to 10 years.

But it is the superb dental arrangement that enabled the hadrosaurs to attain what was virtually global domination of the Late Cretaceous forests and flood plains. Vegetation was cropped by a highly efficient and rugose premaxilla that was covered by a horny sheath – or rhamphotheca to give it its proper name. This was then passed to the dental batteries for processing.

The dental battery of Edmontosaurus

Hadrosaurs employed a unique method of chewing that was a remarkably efficient mechanism, grinding vegetation to pulp. Jaw movement was multi directional made possible by a hinge that was located between its upper jaws and the rest of its skull. This enabled the maxillae to be pushed outwards and sideways, while the dentary teeth ground against the upper maxillary teeth. This grinding action of tooth against tooth ground and shredded the vegetable matter before being swallowed for digestion. This process of oral mastication appears totally unique to hadrosaurs

Interestingly, this process seems to confirm that hadrosaurs had cheeks because if the maxillae hinged outward during chewing, it would seem likely that food would have simply fallen out of the mouth without them! It appears they may have looked a little like they were chewing the cud when eating but, of course, not using the same chewing arrangement as mammals do today. Not for nothing are they known as the cows of the Cretaceous (a rather unflattering description in my opinion).

The tails of hadrosaurs are remarkable feats of structural engineering. A latticework of ossified tendons stretched from the thorax to the anterior tail section and these were held in place by sections of soft tendon which, in tandem with the muscles from the trunk, provided rigidity and stiffness.

This enabled hadrosaurs to be able to walk bipedally by being able to hold the tail horizontal, anchored almost directly from the extremely strong sacral region. The ossification of tendons was an extremely efficient mode of support and acted like a form of cantilever bridge because it was this inflexibility that supported both the tail and torso when the animal moved.

Next time I’ll look at hadrosaurid crests and also discuss the old belief that they were semi-aquatic and how this theory just might be making a bit of a comeback.

Reference

Cooper, LN., Lee, AH., Taper, ML. & Horner, JR. (2008) Relative growth rates of predator and prey dinosaurs reflect effect of predation. Proc R Soc Lond B Biol Sci 275:2609–2615.

Endothermania!

2011-08-10T13:43:00.001+01:00

This is very strange. No sooner have I published the previous post on warm blooded dinosaurs than none other than Greg Paul made a very interesting contribution on the DML. In it, he refers to a paper by Spicer and Herman (2010) that was looking at the Late Cretaceous environment of the Arctic by using plant fossils to determine the conditions at the time.

Migrating dinosaurs are something that has been alluded to in this blog on more than one occasion, usually to explain the occurrence of monotaxic bonebeds that may sometimes contain the remains of hundreds, perhaps thousands of animals. One of these migrations has been suggested to explain animals whose fossils have been recovered from the northern Alaskan slope, in as much that perhaps they spent the summer in northern latitudes during a time of plenty and then returned south before the Winter set in.

Paul points out that conditions in these latitudes were never that warm, with average July temperatures of 50° Fahrenheit (10°c), occasionally hitting 70°f (21°c). A blanket of cloud covered the land, only with occasional breaks, and this combination of average cool temperatures and very little sun were not exactly ideal conditions for ectothermic reptiles and Paul points out that there have been no remains found of crocodile, lizard or turtle on the Alaskan slope.

Winter at these latitudes was hard, at least three months without sun, perpetual darkness and prolonged sub-zero temperatures. Paul interprets these conditions as evidence that dinosaurs were well equipped to deal with such conditions, regardless of whether they were small or large animals, and cites bone histology that displays fast growth which is on a par with dinosaurs living in warmer climates.

And, as Paul points out, there would be no point for dinosaurs at lower latitudes to migrate north since it would be sunnier, warmer and there would be more food simply by remaining where they were. The dinosaurs of the north were resident all year round and maximised the summer season by consuming as much food as possible in preparation for the colder months ahead.

Paul interprets this as powerful evidence of endothermic dinosaurs with a high metabolism that were able to survive in many different environments and suggests that the Spicer paper is, more or less, the final nail in the coffin for those who persist with any notion of ectothermian dinosaurs.

Firstly, it has to be said that Greg Paul loves to throw a notion into the ring to provoke a reaction and this has certainly been the case with this one – just take a look at the follow up emails at the DML, still going strong. Secondly, even if you subscribe to the suggestion that there was no north to south migration, this does not mean that there was not any migration of some description. Surely the huge herds of both ceratopsians and hadrosaurs would have had to keep on the move to some extent otherwise local vegetation would have been quickly exhausted. This is one of those big mysteries that is one of the hot topics of the moment since there appears to be no obvious answer.

It is also worth pointing out that no matter how well sampled a formation may be, something will always turn up that surprises you and it is always a possibility that other reptilian remains have simply not yet been discovered, but this does seem unlikely. As I mentioned earlier, for a full gamut of argument and counter-argument, head over to the DML. Regardless of the evidence, Greg Paul, just like Bob Bakker, loves to get his ideas out there and really stoke up the palaeoworld, which in turn promotes healthy discussion, and I think that can only be a good thing.

Lastly, Paul’s summation echoes my own final words from the previous blog post:

“And the hypothesis of low metabolic rate dinosaurs is dead, dead, dead. Bakker was right.”

Amen.

Reference

Spicer, R. A. and Herman, A. B. (2010). The late Cretaceous environment of the Arctic: A quantitative reassessment based on plant fossils. Palaeogeography, Palaeoclimatology, Palaeoecology, 295(3-4), pp.423–442.

Return of the Warm Bloods

2011-08-03T14:36:00.000+01:00

A couple of recent studies have raised the always interesting question of whether dinosaurs were endothermic or not. Robert Eagle et al of the California Institute of Technology in Pasadena used a technique known as clumped isotope thermometry to discover if the fossilised teeth of sauropods, such as Giraffatitan, Diplodocus and Camarasaurus, could be indicative of body temperature.

What is clumped isotope thermometry (CIT)? In simple terms, CIT measures the reaction and bonding of carbon and oxygen. The technique was being used to determine the temperature of the earth during the prehistoric past when checking for carbon dioxide that was contained within minerals. The isotopes carbon₁₃ and oxygen₁₈ will clump together in low temperatures.

This technique was adapted to measure the mineral bioapatite, which makes up the enamel in teeth and, because bioapatite acts as a thermometer, it was possible to analyze at what temperature the teeth were formed. The results reveal body temperatures in large sauropods ranging from 36° to 38° - exactly the range found in mammals.

Of course, this does not mean that this is conclusive proof of endothermy in dinosaurs but it is further evidence ( if indeed any was needed) that large dinosaurs had a high body temperature and confirms the generally accepted theory that large animals quite naturally have elevated body temperatures anyway. No, the problem is how did animals the size of sauropods actually cool down bearing in mind the variables in sauropod physiology?

In an earlier post I commented that sauropods are engineering marvels and that when the secrets of the sauropods are solved, then we will have answered nearly every other question posed by the dinosaurs all at the same time. Elephants, rhino, hippo and whales suffer from overheating and even sunburn if they are not careful. Elephants cool down because they can pass blood through their greatly enlarged ears and back into the body as it cools. They also wallow in mud and dust which is cooling and gives an element of protection for the skin. And, of course, they are not averse to standing under the odd tree when they can find them.

But sauropods were so big that it is extremely unlikely that they could do any of the above. If they got down to wallow in mud it would seem unlikely that they could ever get up again. They couldn’t cover themselves with dust or mud although there have been the odd theories suggesting that sauropods may have bore a similar trunk to elephants but this seems unlikely and was recently disproved, as do having large ears since only mammals have external ears.

So it seems likely that sauropods had some other way of keeping cool – a technique that is unknown to us at this time. Eagle et al speculate that they may have discharged heat through their long necks and tails or via special air sacs situated below the skin. Worth noting that none of the above take into account the environmental temperature at the time or, something that I’ve been considering for some time, the make up of the atmosphere which was considerably different from today.

More experiments using CIT are to be used on both small and medium sized dinosaur teeth and this will prove very interesting indeed. If the results display enamel forming temperatures that are also at elevated temperatures similar to the sauropods then this would be pretty compelling evidence for endothermy in dinosaurs as a whole.

What do bones tell us?

Another recently announced paper has also added weight to the argument that dinosaurs were endothermic. Roger Seymour et al from the University of Adelaide have discovered that the size of nutrient foramina in human femora is relative to the amount of aerobic activity that can be achieved. The authors have now applied this same technique to determine the aerobic activity of dinosaurs and, unlike the previous work, a range of dinosaurs of different shapes and sizes have been examined.

Blood is supplied by the main artery in the bone through the nutrient foramina to keep the bones in ideal condition and also to effect any repairs that are required. The more active the animal, the more conditioning and repair for the bone is needed, thus the greater the blood supply needs to be. So if the foramina are large, it would appear to show that a much greater degree of metabolic activity was achieved.

Before anything could be determined about dinosaurs, the authors measured multiple femora of extant mammals and reptiles of all sizes, from the smallest to the largest and the results were unequivocal – the larger the foramina, the higher the metabolic rate. Not only that, but the foramina in mammals are about ten times the size of those found in reptiles. So how did the bones of dinosaurs measure up?

Well it turns out that the foramina in dinosaur femora are relatively bigger than even mammals. This has surprised the research team because it indicates that dinosaurs were even more active than the mammals and provides yet more indication that dinosaurs were extremely active creatures and, in all probability, endothermic animals.

The theory regarding hot blooded dinosaurs was part of the original dinosaur renaissance way back in the seventies. It’s been interesting to follow the whole dinosaurian physiological and metabolic argument since Bob Bakker’s original (and groundbreaking) suggestion (Bakker 1972). We have gone through so many different studies and discussions that it has almost become accepted that dinosaurs were something in between ectothermic and endothermic – such as Scott Sampson’s Goldilocks hypothesis (Sampson 2009).

I used to think of this as a cop-out because, despite all the evidence to the contrary ie limb posture, bone histology, fast growth and world wide distribution of dinosaurs, it has generally been hard to accept dinosaurs as fully endothermic. I too have erred on the side of caution and settled for mesothermy – the safe option.

But now, with another two lines of evidence pointing strongly yet again to dinosaurs being highly active, fully developed endothermic animals, how long will it be before we come to accept endothermic dinosaurs? Indeed, how long will it be before we go to Bob Bakker and say “You know – you were right all along!” I hope I’m around to see it.

References

Bakker, R.T., 1972. Anatomical and ecological evidence of endothermy in dinosaurs. Nature 238:81-85.

Eagle, Robert A., Thomas Tütken, Taylor S. Martin, Aradhna K. Tripati, Henry C. Fricke, Melissa Connely, Richard L. Cifelli, and John M. Eiler. Dinosaur Body Temperatures Determined from Isotopic (C₁₃-O₁₈) Ordering in Fossil Biominerals. Science 23 June 2011: 1206196 Published online 23 June 2011 [DOI:10.1126/science.1206196]

Sampson, S.D., 2009. The Goldilocks Hypothesis. In: Sampson, S.D., Dinosaur Odyssey. Fossil Threads in the Web of Life. University of California Press, pp. 175-191.

Seymour, R.S., S. L. Smith, C. R. White, D. M. Henderson, D. Schwarz-Wings. Blood flow to long bones indicates activity metabolism in mammals, reptiles and dinosaurs. Proceedings of the Royal Society B: Biological Sciences, 2011; DOI: 10.1098/rspb.2011.0968

Welcome to Jurassic Park 4?

2011-07-27T14:37:00.000+01:00

Unless you’ve been so far out in the field that you haven’t been able to receive the latest news via the blogosphere and media news pages, then you will know that Steven Spielberg has announced plans for Jurassic Park 4. Spielberg made the announcement during the San Diego Comic-Con and was quoted as saying:

“We have a story. We have a writer who is writing the treatment and hopefully we are going to make Jurassic Park 4 in all our foreseeable futures, hopefully in the next two or three years.”

The first thing to say here is that I wouldn’t hold your breath because JP4 has always been two or three years in the making since JP3 was released way back in 2001. The rumour mill has been rife throughout the following ten years with all sorts of possible story lines, directors and actors – all of which have turned out to be meaningless rumour. But assuming that Spielberg is true to his word, then we can expect another film in the franchise around 2014 which will almost certainly add to the significant global takings by the other three films of $1.9 billion and will no doubt be swelled yet again by the trilogy being released on Blu-ray for the first time later this year.

What has surprised me, however, is the amount of people demonstrating their opposition to the film being made at all, and that is without the criticism of the project that has been demonstrated on social networking sites, blogs and also by the paleocommunity at sites such as the DML. I understand people wanting to protect the legend of the original Jurassic Park but it was inevitable that sequels would be made and that the franchise would escalate. Incidentally, I don’t think the sequels were bad films anyway – they were good fun and entertained people, which brings me too the main point of this post.

The central focus for the anti-JP4 group seems to be the fact that the films were not and will not be scientifically accurate despite the fact that there have been some superb consultants involved from day one including palaeontologists such as Jack Horner. When the original Jurassic Park was released back in 1993, the standard of the effects, attention to detail and scientific accuracy was unmatched – at that time. Subsequently the film was methodically scrutinised and taken apart by both expert and amateur alike and it seemed that, all of a sudden, the film that broke the mould was considered flawed.

By the time JP2 was ready for release the critics were waiting with their sharpened knives in hand, ready to get stuck into it and, unfortunately, the film gave them plenty of ammunition. The biggest concerns at that point were that the raptors were still featherless since the first dinosaur fossils with feathers were already being recovered in China. There’s something about dromaeosaurids portrayed without feathers that really annoys some people – and I mean annoy!

When JP3 went into production it was already being ripped to bits as snippets of information regarding the script leaked out. The film makers were on a hiding to nothing as far as some people were concerned and, despite doing good box office business, the film left a little to be desired as far as some critics were concerned. Although the raptors in JP3 did sport some quills, this was by no means enough.

Now that JP4 has been announced (again) the knives are out once more and you have to ask the question – why? Some people seem to forget that the Jurassic Park movies are made to entertain the public at large – entertain, not to be as scientifically accurate as possible although we would all like to see the situation improve. Not that it would matter if it was accurate since our science is moving so rapidly these days the chances are that a scientifically perfect Jurassic Park would be obsolete within 24 months.

Now I would love these films to be as scientifically accurate as the next man but I accept that this is unlikely because these films are being made to entertain the public at large. Time is money and I suspect that scientific accuracy is somewhat down the priorities list when it comes to getting the film finished and on public release. Even then, these films are a quantum leap better than anything else made and you cannot help but be impressed by the sheer scale and the standard of special effects.

Do I have issues with the Jurassic Park series? Well of course I do and if I am to be pinned down to one inaccuracy it would have to be the Spinosaurus / T.rex conflict in JP3 – not good. That might have worked if the film makers had not depicted the T.rex holding the spinosaur by the neck in its jaws and letting go with absolutely no after affects. In reality the power of the tyrannosaurs jaws would almost have certainly mashed the neck to pulp, perhaps even decapitated it. There would have been no fight to be honest.

The other issue that needs to be raised is that I find it difficult that people see fit to criticise a movie for not being accurate when nearly every single “serious” documentary on television is so often inaccurate, sensationalistic, repetitive and downright misleading. I am always critical of documentary’ s that portray possibility and theory as fact since that is misleading the public in every sense of the word. Most people are not bothered when they are watching the Jurassic Park series since they are at the cinema for the ride – except for us palaeo-types of course!

Come on everyone, film entertainment is exactly that – entertainment. Let’s try and not take them too seriously and enjoy them for what they are. Perhaps when all the serious documentaries are correct then we may have an argument to concentrate on getting the movies right. Incidentally, the two new big television dinosaur documentaries are not too far from broadcasting now and both Planet Dinosaur and Dinosaur Revolution are looking the part. Let’s hope the science is equally as good as the CGI.

Why IS it so Hard to Believe in Gregarious Tyrannosaurids?

2011-07-20T13:44:00.000+01:00

The recent documentary Dino Gangs has met with the usual mixed reaction. The general opinion appears to be that the program (in the UK) was too long by at least an hour and suffered the usual mix of repetitiveness and also that the amount of CGI used was excessive. Still, any new programme on dinosaurs is always welcome and Phil Currie is very watchable.

When discussing the programme with Mark Graham, a colleague of mine, and the newly appointed preparator at the Natural History Museum in London, Mark made a comment which made me take a step back and do a little thinking. He said “How is it that pack hunting in dromaeosaurids seems to be generally accepted but whenever pack hunting is suggested for tyrannosaurids there is always a huge outcry declaring it unlikely?” Good point.

The focus in Dino Gangs is too concentrated on pack hunting tyrannosaurs – something akin to pack hunting in today’s extant mammal populations and yet it is wrong to compare. Don Henderson remarked that the dinosaurian brain was small and relatively underdeveloped when compared to mammals. His observation that "I doubt the thought would cross their tiny reptilian brains" when discussing the possibility of co-ordinated pack hunting tyrannosaurs is probably correct. And yet we should not be too dismissive about the possibility.

It was interesting, however, that throughout the programme, there was not one dissenting voice arguing against tyrannosaurs displaying ANY gregarious behaviour – not one. I accept that the onus was on pack hunting but never the less, perhaps we can take this that there has been a slow acceptance that tyrannosaurs (and other theropods) did gather together for an unspecified amount of time even if it was only briefly, to mate or perhaps to sort out territorial disputes.

Looking at the fossil evidence, there are now many examples of bone beds that contain the associated remains of multiple theropods. Multiple, it should be mentioned, may actually be only two animals but generally speaking when recovering predatory dinosaurs, two is indeed a bone bed. The most famous in recent years is the Albertosaurus bonebed in Alberta, which we now know contains the remains of at least 12 individuals although there are revised figures suggesting more than 20 individuals are represented . There are, however, other examples of tyrannosaurid bonebeds that include the taxa Tyrannosaurus, Tarbosaurus, and Daspletosaurus.

Other theropods found in bonebeds ranging throughout the Mesozoic include Coelophysis in the Triassic, Saurophaganax in the Jurassic and Mapusaurus in the Cretaceous (for an extensive list see Currie 2010). Other evidence for theropods perhaps living in groups includes what I consider to be some of the most compelling evidence and that is the fossilised trackways that are found worldwide. Some of these display tracks of multiple individuals moving together in a uniform direction and which, significantly, do not overlap thus indicating the likelihood that the animals were walking or running together. You also have to bear in mind that other related dinosaurs such as hadrosaurs and ceratopsians have also been found in mass bonebeds containing hundreds, even thousands of individuals. So there is significant fossil evidence that is suggestive that tyrannosaurs did cohabit for an unspecified amount of time.

Moving on to phylogenetic inferance using the extant phylogenetic bracket. Dinosaurs fall between crocodiles and birds and, by inferance alone, can suggest something about the behaviour in theropods, indeed dinosaurs as a whole.

Crocodiles often live together in large numbers but this is not strictly a communal group and is more often than not just an area where they happen to be together usually due to environmental conditions. But at certain times of the year they do gather together in vast numbers to intercept migrating herds of wildebeest and zebra. However they do not pack hunt and prey animals are taken by individuals but the dismembering is very much a joint effort. The seething mass of animals that bite, hold and twist the carcass apart looks as primitive as it gets and yet it is a very efficient way for a number of animals to share the spoils around a large number of animals.

Crocodiles also display amazing courtship, parental care and even a deftness of touch that can be almost regarded as genteel. Courtship is surprisingly complex and includes bubble blowing, slapping the water and vocalising before coupling takes place. The nest of eggs, once laid, is protected by the female and when the hatchlings appear the young are actually carried to nursery pools in the jaws of the female and they benefit from the protection of the mother for a further period of time.

Crocodiles are often imagined to be slow moving, dim witted, cold blooded animals that are throwbacks to the time of the dinosaurs. Well, they outlived the dinosaurs and continue to thrive, often in extreme conditions and are actually a very successful and complex animal. This brings us to the birds.

Birds (which are, of course, surviving avian theropods) also live and breed together in sometimes enormous numbers. In fact the birds often play the numbers game with great success since the more of your fellow birds you breed with, live with or fly with the greater your chances of survival for you and your young are. Birds also display high degrees of courtship and parental care and include some of the most amazing displays of ritual, nest building and care on the planet.

Birds are also known to hunt in groups and, again, complex behaviour is often displayed. Harris hawks hunt in small groups of two to six birds to maximise their chances of a successful hunt in desert terrain. Boobies and gannets also display both visual and oral communication combined with superb diving techniques in often large numbers, again to maximise their efficiency in catching fish. Vultures are very adept in spotting carcasses on the ground and also use their excellent eyesight to spot when one of their number has found such a carcass and join in on the feast almost immediately.

So what about dinosaurs other than theropods? I’ve already highlighted that many species of dinosaur have been found together in large numbers in vast bonebeds. Although these too are studied intensively, there is more acceptance that animals such as ceratopsians and hadrosaurs moved around in large numbers and herds. The numbers of animals in some sites defies belief and that in itself is a huge pointer to gregarious animals moving together.

Of course just why they were moving together cannot be wholly explained because extinct animals and their behaviour cannot be observed as you would observe in extant animals today. It’s easy to imagine migration, breeding and safety in numbers as possibilities for these dinosaurs moving together but it has to remain a point of conjecture that remains impossible to prove.

Parental care in dinosaurs has long been established – to a certain degree. Large nesting sites are known all over the world and in such numbers that almost certainly points to large numbers of animals nesting communally. The Maiasaurs of Egg Mountain are amongst the most famous and fossils here suggest complex parental care. Additionally, and more relevant in this case, are the egg brooding oviraptorids found in the Jiangxi Province of China , which are not that distantly related from tyrannosaurs.

So using the available evidence in combination with phylogenetic inference, it appears to me that the chances of tyrannosaurs living gregariously are very high, indeed maybe should even be expected. For how long a period of time they may of have been together is a matter of conjecture and is impossible to say without direct observation and, until a time machine is invented, that is how it will remain. Quite possibly it was only for short periods such as a mating and breeding season but, on the other hand, there may have been permanent groups of animals living together throughout the year – there is just no way of knowing.

Personally, I do see some tyrannosaurs living in groups for an indeterminate amount of time – but not all. I would also expect a degree of parental care, maybe not as advanced as some birds but nest protection seems likely and maybe feeding and protecting the young as well to some degree.

But what about pack hunting? Impossible to prove and it would appear to be a level of behaviour and coordination above what could be expected of dinosaurs. As things are right now, I see the possibility of communal hunting and feeding which is quite different – more akin to the crocodiles of today. Maybe one tyrannosaur would attack a prey animal and others would join in or, if the prey was injured or cornered, then more tyrannosaurs may have joined the attack and help despatch the unfortunate beast. And again, just like crocodiles, multiple tyrannosaurs ripping in to a carcass would make short work of it and a lot of meat and bone would get shared out real quick. Perhaps the face biting pathologies found in tyrannosaur skulls are actually indicative of this (Tanke 200), as intraspecific squabbling broke out during feeding.

So for me, it’s time to accept that tyrannosaurs and other theropods probably lived in groups for at least part of the time and all the available evidence, albeit circumstantial, suggests there may have been a degree of group hunting but I find it hard to accept that they could hunt in a coordinated, complex manner similar to a pride of lions although, of course, even that cannot be ruled out. Perhaps its time to turn the argument on its head and ask what evidence is there that tyrannosaurs were solitary hunters?

References

Currie, P.J. & David A. Eberth. On gregarious behaviour in Albertosaurus. Canadian Journal of Earth Sciences, 2010, 47:1277-1289, 10.1139/E10-072

Tanke, D.H. & Philip J. Currie. Head-biting behaviour in theropod dinosaurs: paleopathological evidence. Gaia 15: 167-184

Is it time for a Palaeontological Resources Preservation Act in the UK?

2011-07-13T12:23:00.000+01:00

When the global recession hit the UK back in 2008 there was to be a dreadful side effect that has had significant implications for vertebrate palaeontology throughout the country. Many working quarry localities have been closed and with them any more chance of vertebrate material being recovered from these exposures has now gone forever.

And because of these closures, the search for fossils has increased the focus on the already heavily pressured coastal venues. The Jurassic Coast, the Isle of Wight, the cliffs around Whitby and other similar sites have been under the most intense scrutiny in recent years and the pressure is unabating now as more and more collectors descend on the unprotected cliffs and beds.

It is a fact that during the winter, and especially during storms and scouring tides, the competition is at its fiercest and most intense. Indeed, the Isle of Wight has been described to me as “unbelievable” during stormy conditions as an army of lamps and torches turn the cliffs into something akin to a Christmas tree covered by fairy lights – and at 2 o’clock in the morning as well!

How much material of scientific importance has been lost forever? Of course, there are many ethical collectors out there, both professional and amateur and they have made significant contributions to our science. They are not the problem – it is those without any moral obligations that are plundering the sites, collecting for themselves or, as is more and more common these days, collecting to order for clients who are willing to pay a small fortune for a complete ichthyosaur or a partial iguanodontid.

So what is to be done? Can anything actually be done? Well perhaps we can learn a lesson from the United States and use their experience and ideas over here. Early in 2009, the Palaeontological Resources Preservation Act (PRPA) was passed by the House of Representatives and signed by Barack Obama to become law. The PRPA actually consolidated existing practices within the USA by simply making them legally binding, thus enabling the courts to prosecute and sentence those who broke these laws.

It is worth describing the main features of the PRPA before we look at the possibility of utilising some or all of it here in the UK. The main features are:

1) That fossils are a unique and non-renewable resource that provides clues to the Earth’s history and ultimately its future. Very important point this – “non-renewable” – so many people forget this. When they are gone, they are gone forever.

2) Fossils can still be collected from public land but these can only be invertebrate and plant fossils. A reasonable quantity can be taken but they cannot be traded, bartered or sold to anyone else.

3) However, it is forbidden for ANY vertebrate fossils to be removed from public land regardless of whether they are for personal use or to be sold. A permit must be obtained before vertebrate fossils can be collected and these are nearly always issued to professional palaeontologists and they, in turn, must deposit their finds into a professional repository such as a museum or university.

There are other things on the bill but those items listed are the fundamental principles. Interestingly, fossils collected from private lands are not affected, provided you have permission from the landowner – so the commercials and some private traders appear unaffected. And, it must be repeated, that the public can still collect some fossils from public land, provided that it is done sensibly and does not involve the physical alteration of the surrounding rocks to remove the fossils. Surface collecting is the norm.

There have been objections to the bill but these appear to be unjustified and now that the PRPA has settled down, it appears to be working well (I am happy to be corrected here if you know different). The USA has vast palaeontological reserves and these include some of the richest dinosaur hunting grounds in the world and it makes sense to protect them. The UK, on the other hand, is a very small country by comparison and has extremely limited exposures available for research and the collection of vertebrate fossils.

So can the UK implement its own PRPA? Firstly, there are already some initiatives in place but these have only met with limited success. Without the force of the law behind them, people ignore these initiatives and collect. Sites of Special Scientific Interest (SSSI’s) offer some protection and have some legal powers but these appear to be seldom enforced and despite the fact that UNESCO declared the Jurassic Coast a world heritage site, it remains constantly scoured for its treasures.

The south west side of the Isle of Wight - still free to plunder.

Should an almost identical PRPA be adopted in the UK then? Personally, I don’t think it is that necessary whereby all vertebrate fossils are declared “off limits” to the public. I would not want to see the day where a child may pick up that first water rolled ichthyosaur vertebra and be told that they must leave it where it is. Odd elements, teeth, fish spines and scales – I see no problem with these individual fossils being picked up by anybody. It goes without saying that invertebrate and plant fossils could be taken as well.

No, the protection is needed for the more exceptional specimens such as partial and complete skeletons, complete skulls, other associated elements, track ways and other similar fossils. For me it needs to be illegal to remove these specimens without a permit and the proper permission but perhaps, unlike the American system it could be allowed that some non-professional collectors could be licensed because some of them have made fantastic contributions to science over the years. However I would quantify this by agreeing with the PRPA and would insist that all specimens must be deposited into a professional repository.

There will always be the problem of how would we would know when a significant specimen had been removed? Well apart from the physical clues one would hope the public would notify the authorities if they saw something suspicious. And the local collectors aren’t daft – they would know when something is amiss. Someone will always tell someone what they found and excavated – they always do and this will get back to others in the paleoworld. That is why we know that there are so many important specimens in private hands, not just here but all over the world.

I appreciate that a law of this nature can affect a lot of decent avocational palaeontologists out there, people who do have extensive collections and will actually leave their collections to museums, universities and the nation for the benefit of science. It is unfortunate that it could come to this and I would include myself in your number but what is the alternative?

The United States has considerable palaeontological resources – some relatively untouched. They are bigger and so much richer with the amounts of remains in some bone beds defying imagination. The Americans have done something about it and moved to protect them. The UK has little in comparison but is equally as important – and done nothing.

Footnote

Please accept this post for what it is - to promote healthy discussion. It is not intended to offend any well meaning amateur collector or palaeontologist. I simply believe that perhaps it is time for some form of legislation to protect out dwindling fossil resources – before it’s too late.

Remembering Richard Owen

2011-07-06T21:06:00.001+01:00

Richard Owen is a man that needs no introduction in the world of vertebrate palaeontology. Indeed it was Owen who, in 1842, coined the name Dinosauria to represent the order of extinct reptiles that were represented at that time by Iguanodon, Megalosaurus and Hylaeosaurus.

However, Owen is mostly seen as a man who was ruthless, who would stop at nothing to get what he wanted and had no qualms about using close friends and allies to achieve his ultimate goals. Those who dared to take him on were often cast aside and left ruined by a man who knew no limits, took no prisoners. Yes, Owen is often portrayed as the bad guy, the man we love to hate.

Despite this image, we must never forget what a truly amazing man he was and must never underestimate his achievements. Not only did he name the dinosaurs but his work in anatomy, zoology, palaeontology and evolutionary biology is remarkable. Owen introduced us to homology which, in biological terms, means that structures that have the same origin may be used for different purposes or may be morphologically different due to evolution, although Owen, of course, did not recognise evolution as the agent of change. One of the most common examples is that of a bat’s wing and the arm of a man and these are described as homologous structures.

Owen also produced gargantuan efforts as a taxonomist, naming and describing an astonishing amount of taxa through the years. Although he was very lucky in so much of his patronage, Owen also made his own luck as well and because he was made prosector of London Zoo, he was able to expand his knowledge of extant animals simply by being able to access every dead animal that died in the confines of the zoo. Being able to dissect these unfortunate beasts gave him unparalleled knowledge in comparative anatomy and was instrumental in his ability to identify so many new taxa.

To many, his biggest legacy is the Natural History Museum in London, a project that Owen vociferously campaigned for from 1856, through its construction from 1873 to its grand opening in 1881. Although it was initially a wing of the British Museum, the NHM finally achieved independent status in 1963 and is truly a magnificent building, worthy of housing the national collections.

My favourite stories regarding Owen stem back to his youth and the display, even then, of his single mindedness and compulsion to learn more. As a sixteen year old, Owen became apprentice to a surgeon who was charged to treat prisoners in the local jail as part of his rounds. It was here that he had his first encounter with the anatomy of the dead, as those prisoners who had died in captivity were subject to post mortem examination.

Owen was deeply affected by the experience and doubted whether mortal man had the right to defile the dead. He found himself “over-awed by the power of the human corpse” and actually wondered if a career in anatomy was for him. As if to compound his misgivings and fear, Owen, that same evening, experienced yet more terror as he revisited that same jail to treat prisoners with the fever.

Owen found himself in the same building where the earlier post mortems had been carried out – only this time it was dark and his lamp he was carrying had been blown out by the wind. As he fumbled about in the dark, Owen suffered visions that only ones imagination can bring forth and despite coming to realise the reality of his situation, he determined never to desecrate the bodies of the dead again.

Fortunately, this only lasted for about six weeks before his urge to learn more about the human body took control yet again – his burning desire pushing him on. This next story is almost hard to believe except for the fact that it is a perfect example of what Richard Owen was all about.

Owen attended the post mortem of a black patient in the jail hospital and was fascinated. His recent reading of an article describing variety in the human species compelled him to return to the jail on a cold snowy night to remove the head for dissection. He carefully placed the head in a brown paper bag and casually walked out of the jail, passed the guards and out into the night with the bag hidden beneath his cloak!

But as he quickly moved away down the hill, he lost his footing and the head tumbled from the bag and rolled down the hill! The head crashed in to the door of a small cottage and actually pushed the door open. As Owen arrived, the air was filled with the screaming of the lady of the house and, as she ran out, Owen quickly picked up the severed head and ran off.

News of a demonic phantom spread throughout the neighbourhood the following day. Ghost of a pirate captain’s cabin boy was one rumour – the Devil himself others thought. Only Owen knew the truth and he kept the secret to himself for many a year. These early escapades were the blue print for a man who was destined for great things.

In 2009, on the 150th anniversary of Charles Darwin’s publication of Origin of Species, the statue of Richard Owen was removed from its prominent position overlooking the Great Hall in the NHM, and replaced with that of Charles Darwin. I was extremely pleased about this – the proponent of the theory of evolution usurping the man who had done so much to deny it.

And yet I for one do not forget the amazing contribution to science of this most amazing of men and contend that Richard Owen should not be castigated for who he was but rather should be celebrated for what he achieved.

Whither Raptorex?

2011-06-30T12:23:00.000+01:00

In my recent review of Tsuihiji et al's (2011) excellent recent paper on a juvenile Tarbosaurus, I made a reference to the taxanomic status of Raptorex kriegsteini and ended it with the phrase "watch this space" - and here's why:

Fowler DW, Woodward HN, Freedman EA, Larson PL, Horner JR (2011) Reanalysis of ‘‘Raptorex kriegsteini’’: A Juvenile Tyrannosaurid Dinosaur from Mongolia. PLoS ONE 6(6): e21376. doi:10.1371/journal.pone.0021376

Abstract

The carnivorous Tyrannosauridae are among the most iconic dinosaurs: typified by large body size, tiny forelimbs, and massive robust skulls with laterally thickened teeth. The recently described small-bodied tyrannosaurid Raptorex kreigsteini is exceptional as its discovery proposes that many of the distinctive anatomical traits of derived tyrannosaurids were acquired in the Early Cretaceous, before the evolution of large body size. This inference depends on two core interpretations: that the holotype (LH PV18) derives from the Lower Cretaceous of China, and that despite its small size, it is a subadult or young adult. Here we show that the published data is equivocal regarding stratigraphic position and that ontogenetic reanalysis shows there is no reason to conclude that LH PV18 has reached this level of maturity. The probable juvenile status of LH PV18 makes its use as a holotype unreliable, since diagnostic features of Raptorex may be symptomatic of its immature status, rather than its actual phylogenetic position. These findings are consistent with the original sale description of LH PV18 as a juvenile Tarbosaurus from the Upper Cretaceous of Mongolia. Consequently, we suggest that there is currently no evidence to support the conclusion that tyrannosaurid skeletal design first evolved in the Early Cretaceous at small body size.

Another paper of immense interest and freely available at PLoS One here. No doubt there will be further debate and response in the near future which we all look forward to. Now then - was it "Raptotyrannus" or "Nano rex"............?

Reference

Tsuihiji, Takanobu , Watabe, Mahito , Tsogtbaatar, Khishigjav , Tsubamoto, Takehisa , Barsbold, Rinchen , Suzuki, Shigeru , Lee, Andrew H. , Ridgely, Ryan C. , Kawahara, Yasuhiro and Witmer, Lawrence M.(2011) 'Cranial osteology of a juvenile specimen of Tarbosaurus bataar (Theropoda, Tyrannosauridae) from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia', Journal of Vertebrate Paleontology, 31: 3, 497 — 517 DOI: 10.1080/02724634.2011.557116

Prep News

2011-06-29T12:50:00.001+01:00

I finally managed to finish off the prep work on the pliosaur vertebra that I blogged about here. At that point I had more or less finished working on the centrum and had begun work on the neural arch and the remnants of the processes. I was aware just how rare this vertebra was since dorsal vertebrae of pliosaurs are hardly ever found uncrushed in the Oxford Clay and to have one in three dimensions with intact neural canal and processes is unheard of.

Preparation was, however, remarkably similar to working on the centrum. A painstakingly slow process removing matrix piece by piece, almost particle by particle, was followed. Only occasionally did I have the luxury of being able to mechanically remove one or two stubborn spots of matrix with no fear of damage to the specimen.

Although the bone was well mineralised and robust, the surface of the bone could be easily chipped in places if you were not careful. This was especially apparent when cleaning out all the nooks and crannies that were formed during fossilisation as extreme pressures distorted the bone and the cracks that resulted filled with matrix and slowly widened. Every pore of the bone had clay or other matrix in situ and this was prised out speck by speck. These areas were consolidated with Butvar B76 as I went along.

The neural canal itself was the longest job of all. The vertebra had been distorted so that the neural canal was not only compressed mediolaterally but also angled between 5° and 10° rostrocaudally, and this made cleaning out the canal particularly awkward. Removing the bulk matrix from the canal did not pose any particular problems but the finer preparation did, as I struggled to work in a tight enclosed canal with both magnification and light impaired.

Eventually, though, the canal was virtually clear of matrix and I was surprised at how big it was and how deep it ended up, as it plummeted ventrally into the centrum. The rest of the processes were more or less straightforward with only one or two areas of stubborn resistance. Once the prep had been finished, the specimen was gently cleaned and a final coating of consolidant finished the job.

To be honest, there are bound to be a few specks of matrix in situ, especially in the neural canal and I’m sure that I could probably keep on prepping the bone but I am happy that the vast majority of it is fully prepared and that the specimen is complete.

There are many projects still in the pipeline just now and I am particularly keen to start work on an impressive hadrosaur dentary but, the immediate plan is to start work on some associated plesiosaur material that I’ve already alluded to in earlier posts beginning with the stunning humerus pictured below.

As can be seen, this particular bone is virtually complete and is broken in two pieces but the join is excellent suggesting that the fracture has only occurred recently. Preparation would appear to be straightforward although both the proximal and distal ends are somewhat encrusted with shell debris and detritus.

The bone, again, is heavily mineralised and dense and the join will need to be exceptionally strong. To support the bone will require a small purpose built cradle which will needed to be constructed for the task and this will also serve the dual purpose of providing the permanent storage case for the specimen when it is finished.

After the humerus there will be a lot of the other bones from the same forelimb to work on including the radius, ulna, and a host of other associated bones. These too are all well preserved and there appear to be no obvious complications. I will detail these bones as I go along and post periodic updates.

The pliosaur vertebra - as found

More Tyrannosauridae

2011-06-22T13:24:00.004+01:00

From Tsuihiji et al 2011

It cannot have escaped anybody’s attention that there have been a few new tyrannosaur papers this year, two of which I’ll discuss here. The first of these is Tsuihiji et als’ paper regarding a magnificent juvenile specimen of Tarbosaurus bataar from the Nemegt Formation in Mongolia.

I have to say that I really enjoyed this paper and I liked the way it was laid out. Firstly, the identification of the specimen as a juvenile Tarbosaurus had to be established and this was done by comparing it with two other skulls of Tarbosaurus that were adult animals. This direct observation was supplemented by state-of-the-art CT imaging that was overseen by the Witmer Lab.

It was obvious, from day one, that this was a tyrannosaurid and the specimen (Cat. No. MPC-D 107/7) clearly demonstrates numerous synapomorphies that support this affinity. But which tyrannosaur was it? The Nemegt appears to have three confirmed taxa – Tarbosaurus bataar (Maleev, 1955a), Alioramus remotus (Kurzanov, 1976) and A. altai (Brusatte et al, 2009). However, this specimen is from the Bugin Tsav locality and only Tarbosaurus is recovered from here.

Other features such as alveoli count in the juvenile are different from Alioramus and features, that are diagnostic of Tarbosaurus, such as a caudal surangular foramen that is smaller in relation to other tyrannosaurids, are present in the specimen. Combined with the fact that there are several autapomorphies found in Alioramus that are not found in MPC-D 107/7 more or less assures that the animal is indeed a juvenile Tarbosaurus. Estimation of age at death appears to be in the region of two to three years old.

A detailed description of the skull follows and, from a personal point of view, I found it to be one of the better descriptions I’ve read. The spotlight is on ontogenetic differences between MPC-D 107/7 and adult animals and comparisons made using previously described detail including Carr’s craniofacial ontogeny of Tyrannosauridae (1999).

This demonstrated immediately that Tarbosaurus and tyrannosaurids from North America shared a plethora of cranial morphologies during ontogeny. The only significant difference appears to be in the aspect of the antorbital fenestra which does not change greatly in shape in Tarbosaurus but does in their North American counterparts.

Interestingly, the skull lacks specific tyrannosaurid adaptations that allow for the bearing of great stress and torsional forces that are encountered during feeding. In addition, the teeth are much thinner labiolingually and are not as strong and this leads to the conclusion that dietary requirements for this juvenile were different from adults and that they progressively changed throughout ontogeny – not the first time this has been suggested and not just for tyrannosaurids either.

Taxanomic issues raised by the specimen again bring to the fore the status of Nanotyrannus lancensis – the feature this time being maxillary tooth counts and variability within taxa therein. Nanotyrannus has 14 or 15 maxillary teeth whilst Tyrannosaurus has 11 or 12 and here there is a clear difference of opinion as to whether tooth counts vary throughout ontogeny, which suggests Nanotyrannus is a juvenile T.rex (Carr 1999), or whether there is no clear pattern in tyrannosaurids, suggesting that Nanotyrannus is a valid taxon (Currie 2003a, 2003b).

Interestingly, I find both arguments neither correct nor incorrect since they both have merit but, for me, because of the likelihood that individual ontogenetic differences within taxa are highly likely, then maxillary tooth counts cannot be considered as taxonomically diagnostic within Tyrannosauridae – not yet anyway.

Other implications from this study imply more variation in ontogenetic change in tyrannosaurines than previously thought suggesting that tyrannosaurids, as a whole, did not go through a “typical” morphological change as they grew. Also, similarities between Shanshanosaurus huoyanshanensis and MPC-D 107/7 reveal that the former is almost certainly another Tarbosaurus bataar. The status of Raptorex kriegsteini is also considered and after running a phylogenetic analysis, which included MPC-D 107/7, the authors are non-committal although it seems likely that R.kriegsteini is not a juvenile Tarbosaurus. Watch this space.

As I said earlier, I really enjoyed this paper and look forward to the description of the postcrania of this wonderful specimen at some time in the future.

From Tsuihiji et al 2011

Perhaps not as spectacular, but just as fascinating, is the new tyrannosaurine Zhuchengtyrannus magnus, described by Dave Hone et al in Cretaceous Research. The material described is an associated right maxilla and left dentary from Campanian deposits exposed in the Zhucheng quarries of Shandong Province, China and represents a large theropod on a par with Tarbosaurus – perhaps even bigger.

The maxilla displays a maxillary fenestra that is diagnostic of tyrannosaurines but demonstrates sufficient morphological differences from other tyrannosaurines to warrant the raising of a new taxon and includes some unique characteristics.

Although the available material is of limited value to perform a phylogenetic analysis, the specimens, never the less, enable a few assumptions to be made. Firstly, this animal appears to be an adult based on the lack of juvenile characteristics and, of course, there is the size of the bones which are comparable to both Tyrannosaurus and Tarbosaurus. However, Zhuchengtyrannus can be clearly distinguished from Tarbosaurus due to several different characteristics.

As noted in the paper, perhaps the most interesting detail is the fact that there have been remains of a second tyrannosaurid recovered from the same quarry. When you add Tarbosaurus into the mix, then this demonstrates the presence of three large tyrannosaurid theropods living contemporaneously throughout the Campanian.

This is yet another example of an ancient ecosystem with multiple large predators coexisting and the authors highlight other formations that yield such animals such as the Morrison, Two Medicine, Dinosaur Park and Kem Kem Formations. This is what makes the latest Maastrichtian of North America so interesting if, indeed, Tyrannosaurus is the only large bodied theropod in residence.

The implications of this are continually fascinating. How did so many large theropods coexist at the same times? Niche partitioning maybe? Perhaps – and what are the physiological implications for all this, especially if you believe in endothermic dinosaurs? Bob Bakker (1972) postulated that predator-prey ratios were indicative of whether a specific ecosystem was endothermic or ectothermic ie low ratio of predatory animals to prey animals was typically an endothermic community whilst a high ratio of predators to prey animals was indicative of an ectothermic fauna.

Although predator-prey ratios have come under considerable scrutiny over the years and, in some circumstances, considered a flawed analytical tool, it would be interesting to see more research using them, taking into account the faunal increase and turnover in some formations, although sampling bias is often one of the biggest objections to predator-prey analysis. Perhaps it may support theories, such as Scott Sampson’s (2010), that dinosaurs may have been something in between cold blooded and warm blooded – mesothermic he described them.

Whatever the outcome, specimens such as the tyrannosaurids described above can, not only add to our understanding about these animals, but also may help in expanding our knowledge regarding Dinosauria as whole.

Footnote

Make a point of tuning into the Discovery Channel at 9 o’clock GMT on Sunday night for Phil Currie’s latest theories about gregarious tyrannosaurs in Dino Gangs. For a sneak preview, take a look here.

References

Bakker, R.T., 1972. Anatomical and ecological evidence of endothermy in dinosaurs. Nature 238:81-85.

Brusatte, S.L., Carr, T.D., Erickson, B.R., Bever, G.S., Norell, M.A., 2009. A longsnouted, multihorned tyrannosaurid from the late Cretaceous of Mongolia. 1Proceedings of the National Academy of Sciences 106, 17261:17266.

Carr, T.D., 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria: Theropoda). Journal of Vertebrae Paleontology 19, 497:520.

Currie, P. J. 2003a. Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontologica Polonica 48:191–226.

Currie, P. J. 2003b. Allometric growth in tyrannosaurids (Dinosauria: Theropoda) from the Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences 40:651–665.

Hone, D.W.E., et al., A new, large tyrannosaurine theropod from the Upper Cretaceous of China, Cretaceous Research (2011), doi:10.1016/j.cretres.2011.03.005

Kurzanov, S.M., 1976. A new late Cretaceous carnosaur from Nogon-Tsav Mongolia. Sovmestnaâ Sovetsko-Mongolskaâ Paleontologiceskaâ Ekspeditciâ. Trudy 3, 93e104 (in Russian).

Maleev, E. A. 1955a. [A gigantic carnivorous dinosaur of Mongolia]. Doklady Akademii Nauk SSSR 104:634–637. [Russian]

Sampson, S.D., 2009. The Goldilocks Hypothesis. In: Sampson, S.D., Dinosaur Odyssey. Fossil Threads in the Web of Life. University of California Press, pp. 175-191.

Tsuihiji, Takanobu , Watabe, Mahito , Tsogtbaatar, Khishigjav , Tsubamoto, Takehisa , Barsbold, Rinchen , Suzuki, Shigeru , Lee, Andrew H. , Ridgely, Ryan C. , Kawahara, Yasuhiro and Witmer, Lawrence M.(2011) 'Cranial osteology of a juvenile specimen of Tarbosaurus bataar (Theropoda, Tyrannosauridae) from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia', Journal of Vertebrate Paleontology, 31: 3, 497 — 517 DOI: 10.1080/02724634.2011.557116

Plesiosaur Sp. - The Most Common Taxon of All

2011-06-15T12:37:00.000+01:00

Plesiosaur limb morphology is a subject that I have been getting to grips with of late, and what an eye opener that has turned out to be. This has come about because of some recently recovered associated plesiosaur material that a few of us have been looking at and its identification is proving to be troublesome.

Plesiosaurs were a derived group of sauropterygians that used their flippers to, what is known today as, fly underwater. These limbs were used as their principal source of propulsion although it seems likely that there was also an additional tail fin in some cryptocleidoids to provide additional thrust and agility as required (Wilhelm 2010). The limbs were a wonderful design being rigid, paddle-like and elongate.

Unfortunately, this is about as simple as it gets since, as plesiosaurs evolved into more efficient swimmers, modifications to the limb structure, especially to the bones, has made identification of genera problematic. This is amplified when you realise the amount of bone remodelling that occurs throughout plesiosauromorph ontogeny.

Basal plesiosaurs from the Lower Jurassic, such as Plesiosaurus hawkinsi, reveal that the femur and humerus were approximately of similar size. The radius and ulna, in the case of the forelimb, and the tibia and fibula, in the rear limb, were much reduced in size. Postaxially, both the ulna and fibula were remodelled from the basal sauropterygian bone shape and became concave.

These basal plesiosaurs also increased the amount of phalanges throughout their limbs - this is known as hyperphalangy - and they retained this condition throughout their long existence.

More derived plesiosaurs, such as our recent example, display a number of characteristics. The humerus and femur are always less than half the length of the entire limb. Both the front and rear limbs are extremely long due to hyperphalangy as previously mentioned and also, as in basal plesiosaurs, the radius, ulna, tibia and fibula are also significantly reduced in size. Carpal and tarsal identification is somewhat problematic because of remodelling in their morphology.

Collectively, the mesopodials of both the rear limbs and forelimbs are well ossified and are firmly concentrated together. Likewise, the carpals and tarsals are also tightly compacted together. This made for a limb that was rigid and particularly strong and made for very effective swimming throughout the warm Mesozoic seas.

In cryptocleidoid plesiosaurs the fore limbs appear to have provided the majority of thrust since they are bigger than the rear limbs – the humerus is notably bigger than the femur. In pliosaurs it is the reverse and the rear limb appears to have been the main provider of forward thrust.

Although ontogenetic limb ossification is the primary driver of morphological change of bone within the limbs of plesiosaurs, the difference between juvenile and adult plesiosaur limb bones is never the less astounding. Cryptoclidus is the best known of the Oxford Clay plesiosaurs and is represented by multiple skeletons and yet, as with all vertebrate remains, juveniles are scarce. The lack of a decent ontogenetic series of complete specimens causes so many issues when it comes to identification. But the specimens that are available for study do demonstrate the problems faced by palaeontologists.

The Cryptoclidus growth series below from Caldwell (1997) gives an idea of the variability within species throughout ontogeny.

The differences from juvenile to adult are quite extreme. There are enough morphological changes in the humerus and femur alone to cause doubt when trying to establish taxanomic identification – especially when dealing with isolated elements. The other elements such as the mesopodials and metapodials also demonstrate extreme remodelling.

So this particular foray into the world of plesiosaur ontogeny and limb morphology has passed its first phase and we move on forward. Next up is preparation and comparative study of the new material and, if all goes well, the identity of this particular specimen will become apparent.

References

Caldwell, Michael W.(1997) 'Limb osteology and ossification patterns in Cryptoclidus (Reptilia: Plesiosauroidea) with a review of sauropterygian limbs', Journal of Vertebrate Paleontology, 17: 2, 295 - 307.

Wilhelm, B.C. 2010. Novel anatomy of cryptoclidid plesiosaurs with comments on axial locomotion. Ph.D thesis, Marshall University, Huntington, WV. USA

Uncertain Times Ahead

2011-06-08T12:12:00.000+01:00

I’ve mentioned in the past how so many quarries have been lost over the last few years due to the continuous state of our fragile building economy. With so many projects shelved since the Government’s punitive austerity measures it should, perhaps, not be a surprise.

And yet when the current situation improves and we pull out of recession, will the investment and, just as important, the will be there to reopen some of these quarries or will it be seen to be prudent to import material from abroad, whether in its raw material form or, as seems likely, as a processed and finished product?

So many quarries have now shut that some of the most significant inland venues for vertebrate material have already been lost forever. This tragedy is magnified when coupled with the important geological exposures and successions that have also been lost. Simply put, within a very short period of time, the only vertebrate fossil localities that aren’t coastal may very well be a few survivors that are increasingly less inclined to permit access to both geologists and palaeontologists.

And now comes news that one of the last two brick works still operating in the Oxford Clay is to close with the loss of 56 jobs. In reality, the site is officially being mothballed but I fear that this particular works will not reopen. From our point of view, this is worrying since the clay for this works originally came from Quarry 4 and now from Quarry 5.

There have been brick works in the area since the 1800’s and this particular works was still making the famous Fletton brick which has seen a decline in demand for some years now. From a peak of 3,000 million in 1942, demand last year was less than half that figure and has continued to drop by 3% a year.

The Fletton brick is mainly used for repair and maintenance of existing buildings and not for new projects. Something called a flat set brick is now the building brick of choice and the last remaining brick works in the entire area is now due to have significant investment to set up flat set brick production. Quite where this leaves the mothballed site is uncertain at this time.

The fact that investment is being ploughed back into the remaining works is a positive since this should secure the jobs of the bulk of the 269 remaining employees although with proposed shift changes and other “adjustments”, there may yet be further job losses.

So what does this mean for Quarry 5 and the future Quarry 6? Obviously clay is still required for the one remaining brick works, so Quarry 5 will continue to be worked albeit, you would imagine, at a reduced capacity. The next few years are pivotal to the business and would dictate if and when Quarry 6 would need to be opened. If the mothballed works were to be reopened in the future then, all being well, demand for clay would almost certainly increase to levels previously required. At the moment, everything is up in the air so to speak.

From our point of view then, access is being curtailed with immediate effect and the future, instead of being filled with optimism, is now once more filled with not knowing. Indeed, our main champion and supporter of all things palaeontological is one of the casualties of the closure and we are bitterly saddened for him. One thing is certain, however, and that is gaining access to the quarries has just been made a hundred times more difficult than it ever was and I have to admit that denial of entry seems to be the most likely outcome. We will have to wait and see what happens in the short term before planning our next steps.

Learning Curves

2011-06-01T13:05:00.000+01:00

Image from Wikipedia

Victoria Arbour, over at Pseudoplocephalus, recently highlighted a visit to the Smithsonian Museum of Natural History and reflected upon the fact that many people quite often visit a museum to, well, visit a museum, entertain the kids, take a few photos and generally have a good time.

There is nothing wrong with that, of course, but Victoria was questioning the role of museums and suggested that without stopping throughout a visit to take things in, to want to learn and ask questions, to explain things to children, then what does the museum experience actually provide?

Those of us who frequent museums on a regular basis know exactly what Victoria is referring to and I bet that all of us have similar experiences to hers. Firstly, I suggest that this is simply how museums are visited today. A lot of the time, they are simply a place to tick off the list and say “been there, done that”. And this is the same for all museums and not just those that house our beloved dinosaur skeletons.

For instance, we recently visited the RAF museum at Hendon and came across the same apathetic attitude to the exhibits there. The planes on display are, indeed, wonderful and exciting and the exhibits excellent, but there was seldom any discourse between parents and their children. Most of the time, the parents were walking around, taking photos while the kids ran around – no discussion about anything, no parents explaining anything. Of course, not everyone is the same and I delight in listening to parents taking the time and patience to explain things to their children and of course, more often than not, the children respond in kind.

School visits have always been a decent learning tool in my opinion and I have fond memories of my own museum trips. However, the problem today is that, quite often, the amount of children involved on a trip is considerable and they are often only managed by a couple of teachers. Sometimes there may be a couple of volunteers who help with the overall control of the group but controlled education and interaction in such situations is difficult and some children can sometimes feel left out of things , since teachers are so concerned with health and safety issues these days that education suffers as a result. And I am not blaming the teachers for this – the situation simply exists.

And yet throughout all of this, the willingness of both adults and children to learn often shines through. I’ve been approached a couple of times to do a couple of talks on dinosaurs and vertebrate palaeontology for a couple of local societies. This is small potatoes compared to my more esteemed colleagues but I still prepared thoroughly, providing samples and casts of fossils, as well as images and diagrams and, of course, notes for me to refer to throughout.

I was nervous at first but, after the initial early stages had passed, everything became a lot easier and the meetings passed off really well. On both occasions, the question and answer sessions were most entertaining and I was really pleased and, I have to say, pleasantly surprised with the depth of knowledge displayed by some in the audience – and over a broad range of subjects as well.

I hope I’m not sounding too condescending here, it’s just that I wasn’t expecting to be discussing the physiology and metabolism of dinosaurs in such detail and I certainly did not expect to face questions regarding the biomechanics of dromaeosaurid claws. Not my strongest subject so, after some pretty intense discussion, I referred them to Manning (2009) and got out of it that way!

Children have been a delight to work with on the odd occasion that I have done so. Once a year, the local county has an open day that publicises the virtues of different clubs and societies and there are many different exhibits and demonstrations that are all designed to get people involved.

I’ve represented a local geological society a couple of times with a group of colleagues who engage the public to get them interested in geology and palaeontology and to join the society. With stands displaying images of field trips and various meetings backed up with specimens of both minerals and fossils on show, the day always proves to be stimulating and rewarding.

The kids are always great though. We provided a sand pit and hid various fossils in the sand so that they could “excavate” their own fossil. These were all fossils provided by members of the society and were mainly scrappy non-diagnostic bits and pieces that we all picked up over the years, along with the odd sharks tooth.

But the children loved them! They were fascinated by the fossils and quite often asked about what they had found, what part of the animal it was and how old it was. You could see that they were absolutely delighted with their bit of ammonite or belemnite and we genuinely felt that they really had got something out of the experience.

Some older children engaged in questioning us about the fossils and minerals on display and it was again encouraging that they displayed a terrific understanding of the prehistoric past and were thirsty for more. A couple of them were with us for a couple of hours and you could tell that they had reached, without doubt, their happy place. Future geologists and palaeontologists perhaps? I would like to think so.

In the end I suppose we should be grateful that there are both adults and children alike who do indeed want to quench their thirst for knowledge. And if that quick trip to a museum, or maybe that visit to an open day such as I’ve described above, does indeed inspire one person to perhaps become a scientist of the future, then that can only be a good thing.

Reference

Biomechanics of Dromaeosaurid Dinosaur Claws: Application of X-Ray Microtomography, Nanoindentation, and Finite Element Analysis Phillip L. Manning, Lee Margetts, Mark R. Johnson, Philip J. Withers, William I. Sellers, Peter L. Falkingham, Paul M. Mummery, Paul M. Barrett and David R. Raymont Anatomical Record Hoboken NJ 2007 (2009) Volume: 292, Issue: 9, Pages: 1397-405 DOI: 10.1002/ar.20986

The Great Unknowns

2011-05-25T12:30:00.000+01:00

When walking through the great dinosaur halls of the big museums throughout the world, we are often treated to the sight of huge animals that are represented by complete skeletons. And we marvel – not only because of their size but also because we try to imagine these creatures as living, breathing animals.

There are often models, diagrams and paintings showing what these animals were like and information describing what they ate, how they may have reproduced, how they fought, how they moved and even how they may have migrated. To reach these conclusions has been the results of decades of field work, preparation and research and it is fair to say that today we have a pretty sound basis in our understanding of these long vanished animals with a high degree of confidence.

From the early days of vertebrate palaeontological research right through to the present day, the basis for most research has been to compare the fossilised remains of extinct animals with those of extant animals and perform comparative analyses supported by direct behavioural observation of the modern animal. This is known as comparative functional morphology.

When faced with reconstructing an extinct animal, possibly with no extant analogue, it’s normal to start with the basics and try to figure out its habits. Did it live on the land, in the air or in the sea? If a land animal, we should be able to determine whether it was quadrapedal or bipedal, whether it was fleet footed or slow and whether the limbs possessed any other adaptations that may be indicators to its lifestyle.

An aquatic animal may be a permanent inhabitant of the water or may show adaptations that indicate it came onto land on occasion. Wings, of course, are indicative of an inhabitant of the sky but was it a glider or could it sustain a powerful flapping flight?

What did the animal eat? Teeth are the clearest indicator of dietary preference and we can normally specify right away whether the animal is herbivorous or carnivorous. Further study determines what the diet may consist of such as meat, fish, coarse or soft vegetation. Teeth can reveal a lot, even specialist diets can be surmised such as insectivory or omnivory. And, of course, there are the toothless species to take into account.

These are fairly basic assumptions that we can make just by looking at the bones. But pretty soon we start approaching the great unknowns. How would you know if animals lived in herds or were whether they were loners? Did they lay eggs or give live birth? If eggs were laid, were they abandoned or brooded? Were they endothermic or ectothermic?

Fortunately, over the years, there has been more and more evidence to help clear up these matters although there is still much controversy regarding some and, despite the physical evidence, the arguments are not always persuasive. We have many bone beds of several taxa now that are indicative of herding. There are literally thousands of fossilised eggs, some in huge breeding sites that suggest social interaction, brooding and parental care. Significant research into bone histology reveals that dinosaurs were obviously more than ectothermic but whether they were full endotherms is still under the most intense of scrutiny.

Flesh and muscle can be put onto our fossil bones and, fortunately, the scars, lumps and depressions that show where the muscle attachments were fossilise well. Then we come to another great unknown. What was the texture of the skin or hide like? Was it furry, reptilian or were there feathers? Yet again we have been fortunate in some cases. Mummified skin and scale impressions have been found with some dinosaur remains, there are pterosaur specimens with outlines of fur, feather impressions have been revealed in the lithographic limestone from Solenhofen and most recently, and probably most spectacularly, the remains of small theropod dinosaurs from China revealing a wonderful outline of “fuzz” or proto-feathers.

But what about colour? This is virtually impossible to speculate about and remains a great unknown but it is likely that dinosaurs were indeed coloured to some degree since their closest living descendants, the birds, are often brightly coloured. But even here, research moves ever forward (Vinther 2008, 2010 and Zhang 2010) and perhaps we are moving ever closer to the truth.

Ultimately, there will always be an element of uncertainty and great unknowns will remain. For example, if it wasn’t for the exquisitely preserved ichthyosaur specimens from Holzmaden, then it is quite possible that these great marine reptiles would still be displayed in restorations without their dorsal fins and, indeed, the upper tail fluke since only the lower fluke has bone running through it.

For me, great unknowns are best summed up by an example that I recall seeing as a kid and which stuck with me all my life. If our extant elephants were already extinct and we had nothing to compare their bones with, then how on earth would we know that the animal had a long prehensile trunk? The nasal openings are high on the front of the skull and situated between the eyes and there is nothing to suggest the existence of such a trunk. And, when you think about it, the outer ears also leave no physical evidence although I do understand that this is singularly a mammalian trait. Can you imagine our restorations of elephants today if we did not have the modern analogy to compare with?

Yes, I know there are frozen mammoths that have been preserved displaying trunks and ears but the point is essentially correct. It’s an amazing thought that animals such as the dinosaurs, in some cases, may have been even weirder and more spectacular than they already are.

References

• Vinther, J., Briggs, D. E. G., Prum, R. O. & Saranathan, V. 2008. The colour of fossil feathers. Biology Letters 4, 522-525.

• Vinther, J., Briggs, D. E. G., Clarke, J., Mayr, G. & Prum, R. O. 2010. Structural coloration in a fossil feather. Biology Letters 6, 128-131.

• Zhang, F., Kearns, S.L, Orr, P.J., Benton, M.J., Zhou, Z., Johnson, D., Xu, X., and Wang, X. 2010. Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds. Nature 463, 1075-1078 .

Papers and Preparators

2011-05-18T12:53:00.000+01:00

I recently blogged about the importance of keeping good records and documentation for all fossil specimens. Recently this has never been more highlighted since my involvement in the recent excavation of some significant vertebrate material which demonstrated that recording data from the first moment a specimen is found is absolutely essential.

Back in March there was a short but extremely interesting exchange on the Vertpaleo mail listings which came about because of a suggestion that perhaps it was time that scientific publications and papers actually acknowledged the preparator with a line of credit, perhaps attached to an image of the specimen. Although this has improved over the years, with preparators being acknowledged in papers and some also being named as co-author, there is also room for improvement.

And then Steve Jabo, researcher and vertebrate preparator at the Smithsonian Institution, came up with an excellent idea. He suggested that it was time that papers describing new specimens would benefit from an additional section that would include the preparation history of the specimen. This would include techniques, materials and which consolidants and adhesives were used, and the section could be used to aid further research or preparation in the future.

Steve suggested that the preparator could probably put the section together for the paper and that it would therefore always be associated with that particular specimen. This is so simple but the benefits are obvious. For example, if a specimen has had specific chemical treatment or handling, then this information may prevent an alternative form of investigation or conserving technique that may prove damaging.

Even short communications could have these details attached but they would be much more likely to have to be added into the supplementary detail that is normally available on line.

Steve also suggested that perhaps the Society of Vertebrate Palaeontology (SVP) could introduce a new standard to their “Best Practices......” guidelines, providing a basis for standardising such a practice as described. And, not only for new specimens, but also for those previously prepped and researched specimens that may require further conserving or preparation.

In many walks of life there are often sets of rules that we have to follow. Sometimes they are a pain in the backside but, in most cases, they are often sensible and, followed correctly, productive. These are standard operating procedures and they provide a formal set of guidelines for the worker to follow that formalise the same procedures again and again. Consistency being the key word.

It reminds me, in so many ways, of providing a full service history for a used car. Given the choice of a vehicle with such a history, or one with none, you would always go for the vehicle with history. We want to know that it’s been looked after, what repairs it has had and that it has been maintained alright. And this, for me, is the premise of formalising this excellent idea of attaching all the preparation data to the papers concerned.

During this discussion, no less a group including Scott Hartman, Tom Holtz, Andrew Heckert and Jean-Pierre Cavigelli all commented enthusiastically about Steve’s idea and I hope that the movement to introduce this process formally takes shape in the not too distant future.

CJES Vol.47 - Albertosaurus Special Edition - a review.

2011-05-11T13:16:00.000+01:00

Back in September of last year, the Canadian Journal of Earth Sciences produced a special volume devoted to Albertosaurus sarcophagus, specifically to celebrate the 100 year anniversary of the discovery, by Barnum Brown, of the now very famous Albertosaurus bone bed that he found near the Red Deer River in August 1910. Brown excavated the remains of at least nine individual tyrannosaurs and then, for one reason or another, the site got lost in the annals of time until it was famously rediscovered by Phil Currie in 1997.

This volume contains a number of papers that are exclusively devoted to the continual research and findings from this unique theropod bone bed. The volume has been specially edited by Currie and Eva Koppelhus with associate editing by Hans-Dieter Sues and they have amassed an impressive array of researchers to contribute to the volume.

The stratigraphy, sedimentology and taphonomy is looked at in considerable detail by Eberth and Currie and by combining the evidence from all three disciplines, they deduce that these tyrannosaurs were killed by a major storm event that was capable of uprooting trees and flooded much of the landscape, thus drowning these animals. Papers from Koppelhus and Braman and Larson et al also make significant contributions that enable us to successfully visualise in detail the palaeo-environment that these tyrannosaurs were part of.

These albertosaurs lived in a cool, dry climate that was becoming progressively warmer and wetter. Interestingly, Larson et al suggest that since the differences in fauna between the late Campanian and early Maastrichtian are so slight, that it is likely that environmental conditions were responsible for those that did occur as opposed to faunal turnover.

Tanke and Currie’s history of Albertosaurus discoveries is thorough, as you would imagine, and I particularly liked this paper since I do enjoy the history of dinosaurian discoveries. Indeed Darren’s work is always worthy of special mention and I am a huge admirer of his dedication and work ethic. I’ve blogged recently about Thomas Carr and am a confirmed follower and his contribution to the volume is his reassessment of the taxanomic affinities of Albertosaurus sarcophagus. Carr identifies the palatine and maxilla as diagnostic of the species and not only confirmed that the tyrannosaurids of the bone bed are indeed Albertosaurus sarcophagus but is also able to confirm that both the type (CMN 5600) and paratype (CMN 5601) are definitely referable to the taxon. Lots of detail including stratigraphic distribution and ontogeneric change make this paper a must read.

Some highly detailed work by Buckley et al look at tyrannosaurid tooth morphology using the multitude of specimens recovered from the bone bed that represent both adults and juveniles and conclude that variation in morphology occurs throughout ontogeny. Indeed, some of the tooth morphology is so extreme that specimens could be mistaken for either aberrant tooth morphologies or maybe even a new species. Only because the bone bed represents so many different individuals of different ages could these conclusions be made. Miriam Reichel also looks at teeth but this time looking at tyrannosaurid heterodonty using digital 3-D models. By comparing albertosaurine (A. sarcophagus) and tyrannosaurine (T.rex) teeth, Reichel confirms heterodonty and that tooth morphology and purpose is sensitive to the proportion of the jaw.

Phil Bell looks at a few of the bone bed elements that display paleopathologies and, whilst always fascinating, there are not enough elements to draw any satisfactory conclusions except, of course, that maybe this group of tyrannosaurs may have been in good health. Always hard to call, this sort of observation. Erickson et al look at the life expectancy curve of Albertosaurus sarcophagus since the number of recognised individuals in the quarry has now increased since 1997 and compared these details with results from earlier studies. These reveal that young albertosaurs had a (surprisingly) low mortality rate (3.47%) from ages two to thirteen but an increase in mortality rates to almost 20% from mid-life to death, which is postulated to be around 28 years of age. This may be due to animals becoming sexually mature and enduring all the rigours and challenges that reproduction represents. Also of interest is that if juveniles survived their first couple of years then they would invariably get to about 15 years of age and this appears to be the average life expectancy and it is expected that very few albertosaurs would make the maximum expected age of 28.

Finally, Currie and Eberth look at the possibility of gregarious behaviour in Albertosaurus and conclude that these tyrannosaurs were indeed gregarious to some degree. As we all know, and I continue to point out, any behavioural implication can only be inferred but I have to say that I do agree with the authors. A combination of osteology, ontogeny and sexual variation in skeletons, as well as evidence of intraspecific combat such as face biting, all suggest social interaction of some sort. The authors, however, maintain that the biggest pointer to gregariousness is the fact that the prey animals moved in herds and that it made good sense to hunt in numbers. How sophisticated this gathering may have been is impossible to quantify but there is sufficient implication from extant animals, such as birds and crocodiles that give some idea how this may have occurred.

In conclusion then, I have only scratched the wealth of information that is enclosed in this unique volume and, if like me, you are a follower of tyrannosaur research, then I can heartily recommend the volume. The amount of data provided is astonishing and it is only when you read a unique publication, such as this one, that you can appreciate the amount of work, research, time and effort that goes into the study of a bone bed such as this. All this and an awesome Michael Skrepnick cover as well. Recommended.

References

Phil R. Bell. Palaeopathological changes in a population of Albertosaurus sarcophagus from the Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. Canadian Journal of Earth Sciences, 2010, 47:1263-1268, 10.1139/E10-030

Lisa G. Buckley, Derek W. Larson, Miriam Reichel, Tanya Samman. Quantifying tooth variation within a single population of Albertosaurus sarcophagus (Theropoda: Tyrannosauridae) and implications for identifying isolated teeth of tyrannosaurids. Canadian Journal of Earth Sciences, 2010, 47:1227-1251, 10.1139/E10-029

Thomas D. Carr. A taxonomic assessment of the type series of Albertosaurus sarcophagus and the identity of Tyrannosauridae (Dinosauria, Coelurosauria) in the Albertosaurus bonebed from the Horseshoe Canyon Formation (Campanian–Maastrichtian, Late Cretaceous. Canadian Journal of Earth Sciences, 2010, 47:1213-1226, 10.1139/E10-035

Philip J. Currie, David A. Eberth. On gregarious behavior in Albertosaurus. Canadian Journal of Earth Sciences, 2010, 47:1277-1289, 10.1139/E10-072

David A. Eberth, Philip J. Currie. Stratigraphy, sedimentology, and taphonomy of the Albertosaurus bonebed (upper Horseshoe Canyon Formation; Maastrichtian), southern Alberta, Canada. Canadian Journal of Earth Sciences, 2010, 47:1119-1143, 10.1139/E10-045

Gregory M. Erickson, Philip J. Currie, Brian D. Inouye, Alice A. Winn. A revised life table and survivorship curve for Albertosaurus sarcophagus based on the Dry Island mass death assemblage. Canadian Journal of Earth Sciences, 2010, 47:1269-1275, 10.1139/E10-051

E. B. Koppelhus, D. R. Braman. Upper Cretaceous palynostratigraphy of the Dry Island area. Canadian Journal of Earth Sciences, 2010, 47:1145-1158, 10.1139/E10-068

Derek W. Larson, Donald B. Brinkman, Phil R. Bell. Faunal assemblages from the upper Horseshoe Canyon Formation, an early Maastrichtian cool-climate assemblage from Alberta, with special reference to the Albertosaurus sarcophagus bonebed . Canadian Journal of Earth Sciences, 2010, 47:1159-1181, 10.1139/E10-005

Miriam Reichel. The heterodonty of Albertosaurus sarcophagus and Tyrannosaurus rex: biomechanical implications inferred through 3-D models. Canadian Journal of Earth Sciences, 2010, 47:1253-1261, 10.1139/E10-063

Darren H. Tanke, Philip J. Currie. A history of Albertosaurus discoveries in Alberta, Canada. Canadian Journal of Earth Sciences, 2010, 47:1197-1211, 10.1139/E10-057

A Stunning Juvenile Tyrannosaurid

2011-05-10T09:38:00.000+01:00

This was the talk of the palaeoworld and blogosphere late last night. Published on line last night in the latest Journal of Vertebrate Paleontology is the long awaited paper by Tsuihiji et al describing a wonderful example of a juvenile Tarbosaurus bataar from the Nemegt Formation in Mongolia. Expect copious amounts of coverage over the next few days and weeks and no doubt expect me to comment in the not too distant future.

Awesome material backed up by stunning digital rendering by the Witmer Lab. Here’s the abstract:

Abstract

A juvenile skull of the tyrannosaurid Tarbosaurus bataar found in the Bugin Tsav locality in the Mongolian Gobi Desert is described. With a total length of 290 mm, the present specimen represents one of the smallest skulls known for this species. Not surprisingly, it shows various characteristics common to juvenile tyrannosaurids, such as the rostral margin of the maxillary fenestra not reaching that of the external antorbital fenestra and the postorbital lacking the cornual process. The nasal bears a small lacrimal process, which disappears in adults. Lacking some of the morphological characteristics that are adapted for bearing great feeding forces in adult individuals, this juvenile specimen suggests that T. bataar would have changed its dietary niches during ontogeny. The numbers of alveoli in the maxilla (13) and dentary (14 and 15) are the same as those in adults, suggesting that they do not change ontogenetically in T. bataar and thus are not consistent with the hypothesis that the numbers of alveoli decreases ontogenetically in tyrannosaurids.

Reference

Tsuihiji, Takanobu , Watabe, Mahito , Tsogtbaatar, Khishigjav , Tsubamoto, Takehisa , Barsbold, Rinchen , Suzuki, Shigeru , Lee, Andrew H. , Ridgely, Ryan C. , Kawahara, Yasuhiro and Witmer, Lawrence M.(2011) 'Cranial osteology of a juvenile specimen of Tarbosaurus bataar (Theropoda, Tyrannosauridae) from the Nemegt Formation (Upper Cretaceous) of Bugin Tsav, Mongolia', Journal of Vertebrate Paleontology, 31: 3, 497 — 517 DOI: 10.1080/02724634.2011.557116

Harley Garbani - A Few Thoughts

2011-05-04T12:21:00.000+01:00

I was saddened to hear about the death of Harley Garbani a couple of weeks ago. He was 88 and died from natural causes. It was good to see that his passing was marked by a number of publications and that the palaeo-world was universal in its appreciation of his amazing talents.

Harley was a man who inspired others and is another example of someone who applied himself after graduating from high school and did what so many of us aspire to, namely to become a self-taught palaeontologist. Harley’s discoveries over the years are legion and many of his discoveries are on display in such repositories such as the Museum of the Rockies, the University Of California Museum Of Palaeontology and, the institution he was mostly associated with, the Natural History Museum of Los Angeles County.

I first became aware of Harley during yet more tyrannosaur research. I was particularly looking at a specimen of Tyrannosaurus rex (LACM 23844) which was of considerable interest since the quarry had also produced a second tyrannosaur and theropod bone beds are exceptionally rare. Although I didn’t know at the time, this was actually Harley’s most memorable find.

During 1966, Harley set out to specifically locate a T.rex specimen, if it were possible, and decided very wisely, not only to go blindly prospecting in the Missouri Breaks of eastern Montana, but also to cultivate the knowledge of the local ranchers and the people of Jordan. He became a temporary “Jordanian” and got to know the locals, enjoying both a drink and their company, all the while listening out for any clues that would help in his quest.

Harley met rancher Lester Engdahl and it was this meeting that was to lead to his fist T.rex. Engdahl’s ranch was around 20 miles northwest of Jordan and Engdahl had commented that he had seen some strange bones on his land. Harley knew that this could be the break he was looking for and was soon scouring the area. On July 27th he spotted what appeared to be a massive toe bone eroding out of some mudstone. In his journal Harley recorded:

“About 3 p.m. over north of the dam, I ran into what I believe is limb and tarsal and two toes of the hard to find rex”

The remains did indeed turn out to be T.rex - only the third specimen recovered from the Hell Creek Formation and was an important specimen. The remains were excavated over several field seasons and amount to about 25% of a skeleton although the skull was fairly complete and there are casts of the skull in museums all over the world.

Although LACM 23844 is Harley’s most famous find he has been instrumental in locating many other significant and important discoveries. A skull of Edmontosaurus annectens (LACM 23502) is unique because it preserves evidence of the horny sheath that covered the beak. Thescelosaurus garbanii was named after Harley and became the second named species of this dinosaur although this animals taxanomic affinities have often been subject to intense scrutiny. The specimen (LACM 33542) represents an animal some 15 feet long which is somewhat large for a hypsolophodontid.

In 1997 he discovered the disassociated remains of what appeared to be a pachycephalosaurid but when pieced together they proved to be from the smallest Triceratops skull ever discovered, about a foot long and only missing the nose and beak. A further two Tyrannosaurus specimens can be added to his impressive tally and this includes LACM 2841 which is estimated to represent an individual of only two years of age. All of these specimens and more are testimony to Harley Garbani’s astonishing ability at finding unique and important fossils.

Harley was also an accomplished preparator and was renowned for his eye to detail and his astonishing technique. He also collected mammals and other fossils as diverse as clams, snails and plants. He was a recognised expert in Native American archaeology and amassed a significant collection of artefacts.

Harley had several specimens named after him such as the aforementioned Thescelosaurus garbanii and others such as Geomys garbanii (a type of gopher) and Elomeryx garbanii – a kind of hippopotamus. In all, there are seven species that bear his name. Never was tribute more deserved. But he will always be remembered for his dinosaur discoveries and the world of palaeontology is worse off for his passing.

Footnote

LACM 23845 was also discovered by Harley Garbani from the same quarry as the previously mentioned LACM 23844 and was actually discovered in the overburden that was covering the original specimen. This was the holotype of Albertosaurus megagracilis but is generally accepted to be a juvenile Tyrannosaurus rex.