Two bits of science news today. First, my Chicago colleague Paul Sereno and his team have revealed the fossil of a tiny Tyrannosaurus-rex-like dinosaur. Named Raptorex kriegsteini, it’s 1/100th the size of T. rex (they’re talking body mass here, not linear dimension). Over at the Guardian, you can read a precis of the Science Express article and watch a video of the ever-telegenic Sereno describing the beast, its significance, and how he procured it.
Like many recent dinosaur fossils, Raptorex comes from China. The fossil dates from about 130 million years ago. This antedates T. rex by nearly 60 million years! (The authors speculate that Raptorex could indeed be an ancestor of T. rex.)
Raptorex was roughly 3 meters long, weighed about 65 kg, and the individual is estimated to be about 5-6 years old. There is no sign of feathers on this specimen, though bipedal predatory dinosaurs of that era have shown feather impressions when preservation was good.
The critical aspect of this tiny rex is its possession of several features thought to have evolved only in its later relative as adaptations for being a large-bodied predator. These include a proportionately large and heavily-muscled skull, tiny forelimbs (note that in the video Paul says they were NOT vestigial!), premaxillary teeth shaped like incisors, and hindlimbs that enabled it to run quickly. We know now that these features were also perfectly useful for the smaller Raptorex. As Sereno et al. note in the paper:
Raptorex in sum, reveals that the tyrannosaurid morphotype . . .evolved at modest body size some 125 million years ago. These features, singly or in concert, can no longer be explained as a passive, allometric consequence of body size increase or the product of an extended (peramorphic) growth trajectory Instead, these features seem firswt to have evolved as an efficient predatory strategy at relatively small body size. It remains to be seen whether miniature precursors like Raptorex eventually will be discovered for other large-bodied predatory radiations among dinosaurs, such as abelisaurids, spinosauroids (megalosauroids), and carcharodontosaurids.
Fig. 1. Raptorex (photo from New York Times article).
And what would science news be without felids? The BBC News reports that the rare and elusive African golden cat (Profelis aurata), has been photographed in the wild for only the second time in history, deep in the Ugandan jungle. The pictures are not in color, and in the photos look disappointingly like a cougar, but have a gander. Here’s what the beast looks like in color:
Fig. 2. Profelis aurata (Wiki article here.) Individuals weigh between 15 and 30 pounds.
Sereno, P.C., L. Tan, S. L. Brusatte, H. J. Kriegstein, X. Zhao, K. Cloward. Tyrannosaurid skeletal design first evolved at small body size. Science online, Sept 17, 2009.