Wednesday, April 29, 2009

New tyrannosaur described

I can't find a good image online (yet) but a new tyrannosaur, Xiongguanlong baimoensis has just recently been described, coming from the Albian/Aptian time frame (border between Early and Late Cretaceous---or, although there's no technical epoch named this for some reason, it's right in the middle of the Cretaceous at roughly 100-125 million years ago) from China.

According to most commonly accepted cladograms today (I think the Thomas Holtz 2004 cladogram of the tyrranosaurs seems to be the one I see touted most frequently) the tyrannosaurids proper are nested within the tyrannosauroids. Xiongguanlong would be a very late tyrannosauroid leading up to becoming a tyrannosaurid; it's growing in size and scope to be less like the small and gracile early forms and becoming more of a large apex killer. It's been compared to both Alioramus and Appalachiosaurus, the former being a late appearing atypical form that's poorly known (from only a single, incomplete and possibly juvenile specimen) and the latter being an early, long-snouted form that's seen as leading up to the rest of the Late Cretaceous tyrannosaur clan, prior to the tyrannosaurine and albertosaurine split.

I don't know yet that this is an exciting find as far as dinosaur specimens go, or one that changes our understanding of anything, like little Tianyulong that I talked about a few weeks ago, but hey, it's a tyrannosaur, and everyone loves a tyrannosaur, right?

I'm actually a bit atypical there. I mean, I like tyrannosaurs well enough, and what red-blooded dinosaur guy doesn't, but my real love amongst the dinosauria belongs to the carnosaurs. There's something about the big guys, following after and chasing down what seems like it should be impossible prey in the form of the sauropods, that really appeals to me. It's the most classic and iconic dinosaur image I can think of (actually, that'd probably be some sauropod rushing off into the water with a carnosaur standing there impotently bellowing its rage at them from the shore---nobody believes that scenario anymore, though) and therefore a staple of why I love dinosaurs so much in the first place.

It used to be that any big, meat-eating dinosaur was called a carnosaur, but it was probably obvious (even to anyone working at the time) that that couldn't possibly be a natural group. When someone says carnosaur today, they really mean Allosaurus and his cousins, the biggest and most advanced of which are the carcharodontosaurs coming out of South America and West African quarries from the middle of the Cretaceous like Carcharodontosaurus, Giganotosaurus, Mapusaurus and Tyrannotitan. North American Acrocanthosaurus may or may not have been a carcharodontosaur (it may also have been a derived allosaur), and is probably also responsible for the famous Paluxy trackway, where it supposedly attacked a sauropod (probably a Pleurocoelus or possibly a Sauroposeidon.)

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