Thursday, 29 September 2011

Watchet & Kilve


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


Thursday, 22 September 2011

Tyrannosaurid Forelimbs - Why, What or Something Else?

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, 21 September 2011

Wednesday Night is Dino Night!

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!

Thursday, 15 September 2011

Fossil Teeth Reveal So Much Data


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.

Sunday, 11 September 2011

Planet Dinosaur Arrives

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?

Wednesday, 7 September 2011

Hadrosaurs - Underrated Yet Spectacular (Part 2)

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.


Image courtesy of Tommy Bradley ©


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.

Image courtesy of Tommy Bradley ©

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.