Empire of the Shark Teeth

Today saw the publication online of a paper finally re-describing Chilantaisaurus maortuensis, a theropod from mid-Cretaceous China. This species was assigned to the genus Chilantaisaurus in 1964 by Hu, and has been all over the map since then. Authors have variously considered it a tyrannosaur, an allosaur (linking allosaurs and tyrannosaurs, actually), and even a maniraptoran coelurosaur. While the exact identity of Chilantaisaurus proper remains a bit uncertain (latest word is that it may be a spinosaur), the new paper is pretty sure of its conclusion: C. maortuensis isn't Chilantaisaurus at all, but the first known Asian carcharodontosaur!

As the story goes (and as Steve Brusatte reported in a guest post at Archosaur Musings), during some down time in Beijing, and while working on his PhD thesis on tyrannosaurs, he got wind of this possibly tyrannosaurian specimen at a Beijing museum. It was immediately apparent to his eye that this was not a tyrannosaur, but a carch, which he and his colleagues finally renamed as Shaochilong maortuensis.

Not only is this the first Asian carch, but it fills a glaring hole in the Asian fossil record. Basal tetanurans dominated the large carnivore roles of Asia in the Jurassic, and tyrannosaurs like Tarbosaurus and Alioramus dominated in the Late Cretaceous. But what was going on in the mean time? Apparently, carcharodontosaurs, which were previously only known from the Americas, Europe, and Africa. This means that tyrannosaurs didn't arrive on the scene until the very end of the Cretaceous, much later than previously thought. Part of this has to do with the dating of the Ulansuhai Formation where Shaochilong was found. Previously thought to be Aptian-Albian in age, dating of underlying rocks shows that it must be at least Turonian (92 Ma), pushing the arrival of tyrannosaurs well into the Late Cretaceous.

So, did tyrannosaurs arise in Asia, migrate to North America, then migrate back to dominate Asia in the LK? We'll need more fossils to know the whole story. Given the Cretaceous age of Shaochilong, we can't be sure whether carcharodontosaurs originated in Asia or migrated there from Europe, Africa, or North America, all of which have earlier carch species. But, as a special bonus as Steve points out on the blog linked above, this presents the first evidence that carcharodontosaurs could have battled ceratopsoids (in the form of Turanoceratops), horning in (haha, get it?) even further on traditional tyrannosaur territory.

Speaking of Asian tyrannosaurs, have you heard about that gorgeous complete Alioramus skull recently auctioned off to a private collector and thus lost to science for probably ever? Well don't cry too much over it. More to come...

[Image: Chilantaisaurus from here.]