Wednesday, 21 August 2013

Duelling Dinosaurs? Don't Believe The Hype

The so-called “Duelling Dinosaurs of Montana” have been in the news again but for all the wrong reasons. The specimens are being offered up for auction at Bonhams on November 19th with an estimated sale price of between 7 to 9 million dollars. The fossils which were found in 2006 on privately owned land are purported to represent two taxa – one the somewhat notorious Nanotyrannus lancensis (the so-called “pygmy tyrant”) and the other an as yet unnamed chasmosaurine ceratopsid.
Regardless of anyone’s feelings about the selling off of what is obviously an exceptional fossil pair we have to accept that this is an entirely legal and above board transaction unlike the very well publicised and highly illegal smuggling and auctioning off of a very fine specimen of Tyrannosaurus bataar last yearwhich ultimately ended up with the arrest and conviction of the main protagonist involved and the specimen being returned to Mongolia.
Now we do not have to like it or accept it but until there is a change in the law then these very high profile auctions with unique fossils will continue to occur – indeed there is yet another Triceratops skull up for auction at Christies in London in September. In this case, however, I do object to the apparent perception that the tyrannosaur is indeed a specimen of Nanotyrannus and the ceratopsid is a new chasmosaurine. Just take a look at the raft of news reports pertaining to these fossils and they all, virtually to a man, accept as gospel that the two specimens are Nanotyrannus and a new chasmosaurine. No doubt as a result of a finely tuned publicity machine designed to maximise the profit – very sad.
The truth, however is probably somewhat different. The Hell Creek Formation (HCF) is one of the most heavily sampled formations on the globe. Every year the exposure host many field expeditions, both academic and commercial, and every year there is a vast amount of research dedicated to the dinosaurs and other inhabitants of this exceptional treasure trove of fossils. Chief amongst these is the Museum of the Rockies and they have amassed one of the finest collections of Hell Creek dinosaur fossils in the world.
This collection has enabled Jack Horner, his fellow researchers and students an unparalled data resource that has been amassed over the years and the Hell Creek Project (1999 – 2010), which was a collaborative project with other institutions, produced the most comprehensive survey of the HCF ever made and included all disciplines including geography, taphonomy, stratigraphy, phylogeny, and ontogeny and this allowed the researchers to determine how abundant dinosaur skeletons were throughout the whole of the HCF.
And this is the important part – the whole of the HCF. In other words the lower, middle and upper Hell Creek Formation and not just a particular bed or section. Of course there is nothing wrong when assessing a section of the HCF but when you do not take the entire formation into account then your dataset can be misleading and errors occur.
Now regardless of whether you agree with a lot of the research and theory that has been published over the last few years is somewhat mute at this point. The controversial Triceratops/Torosaurus synonymy debate is a case in point and has featured here on this blog many times but the important point remains – that is this hypothesis was formulated because the researchers had a huge amount of data at their disposal simply because they had a vast quantity of fossils to examine which represents the largest Triceratops ontogenetic sequence ever accumulated.
So if you bear that in mind that all of these fossils have been gathered over the 12 year period of the Hell Creek Project, carrying on to the present day and then include the incredible amount of fieldwork that has been done throughout the twentieth century you have to ask yourself a question. Where are all the Nanotyrannus fossils and, apart from Triceratops, where are the other chasmosaurines in the formation?
I understand the possibility that certain dinosaurs may inhabited specific habitats. Some may have lived at higher levels away from the coastal plains and thus fossilisation would be greatly reduced. This has been suggested to explain the dearth of Nanotyrannus fossils but, when you think about it, that does not really work in any other dinosaur bearing formation in the world – especially with theropods. Large sympatric theropods are the norm now and there is lots to discuss on this issue in the near future (lots of cool research too).
So for Nanotyrannus we have the Cleveland skull (CMNH 7541) and nothing else. If you subscribe to Thomas Carr’s work, as the majority of tyrannosaurid workers do, then his 1999 paper looking at tyrannosaurid craniofacial ontogeny demonstrates that the Cleveland skull is a juvenile Tyrannosaurus, thus Jane (BMRP 2002.4.1) is a juvenile Tyrannosaurus and, ergo, this duelling tyrannosaurid is certainly another juvenile specimen of Tyrannosaurus – which would still be a very important specimen.
There is a really interesting way that the possible identity of the duelling tyrannosaur could be ascertained. Jack Horner and his team have made vast inroads into the world of bone histology at the Museum of the Rockies and, as you will have seen in the many publicity shots of the specimen, there are long bones present, so why not section one of them, check out the histology and if the results show this specimen is an adult then it would confirm the existence of Nanotyrannus and we can finally put this debacle to bed. 
But that won’t happen because a) it would affect the dollar value of the specimen and b) it would show up as a juvenile tyrannosaurid anyway. As always with Nanotyrannus I would be very happy to be proven wrong but the onus is very much on those who maintain its validity. At school my teachers would not accept that I could perform a sum in my head ( although I could) and were always saying “Show me how you worked that out” and that is what the challenge is to proponents of Nanotyrannus – show us your working out!
Just because it is a small tyrannosaurid does not make it a new taxon – goodness that is something the Hell Creek Project has clearly shown. However, I fear that the myth is far too valuable to protect and, despite the amount of evidence to the contrary, will continue to be perpetuated.
In the case of the “new” chasmosaurine the situation is even worse. How many specimens of Triceratops have been pulled from the HCF? Must be in the hundreds now (nobody actually knows). How many other chasmosaurines? None. In fact the only ceratopsid throughout the Hell Creek is Triceratops – period. So that narrows down the identity of the duelling specimen somewhat.
The supposed hypothesis leading to the basis for suggesting that this specimen represents a new taxon is based on a selection of ontogenetic and morphological disparities that are not conducive with known Triceratops fossils. Really? You do surprise me…..
With ceratopsians in particular it is extraordinarily dangerous, especially with what we know now, to base your assumptions on parts of the skull, including the parietal and horn cores, which are subject to enormous variation because of ontogeny and individual variation. You just cannot do it and, just as with the tyrannosaurid, small does not necessarily mean new. More histology required here methinks…..
So, although the specimens are both important, they are almost certainly not what they are being made out to be. And, on top of that, they are almost certainly not “duelling dinosaurs”. No the truth is probably much more mundane and they were simply two carcasses that got washed up together prior to being fossilised. Sometimes the truth is actually much simpler than people want to believe.
Carr, T. D.  1999.  Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Theropoda). Journal of Vertebrate Paleontology 19:497-520.