This week's Nature announces Guanlong wucaii - the oldest member of the tyrannosaurid family. Here is the abstract and a news release (Nature iniitally embargoes electronic copies), and the takes from New Scientist and FoxNews - with an artist's rendering.
Tyrannosaurus rex was the largest and one of the last tyrannosaurids, living in the late Cretaceous period right up until the extinction of the dinosaurs 65 million years ago. (Yes, the Jurassic Park book and movie series took a little license).
This find pushes back the lineage of the tyrannosaurids from the early Cretaceous (130 million years ago) to the mid-Jurassic (160 million years ago). It also points to an Asian rather than a North American origin.
What is probably most interesting is that this find confirms the recent shift of tyrannosaurids from the carnosaur to the coelurosaur lineage. This is the line from which birds descend, and also that which contains the feathered carnivorous dinosaurs found over the last generation.
Dinosaurs are divided into two groups on the basis of hip structure: the ornithischians (non-long-necked plant eaters) and the saurischians. The latter subdivide into the sauropods (long-necked plant eaters) and the theropods (meat eaters). The latter subdivides again into carnosaurs and coelursaurs. The former are stocky and the latter are gracile. Until recently it was thought that tyrannosaurids were carnosaurs, but it now appears that this lineage peaked with Allosaurus 70 million years earlier. Interestingly the delicate bird-like bones of coelurosaurs allowed them to grow both larger and smaller than carnosaurs.
Further, this is also the group containing the raptors, which are believed to have been pack hunters; an idea that dovetails nicely with recent conjecture that tyrannosaurids hunted in family groups of swift youngsters with sturdier parents closing for the final kill.
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