Tiny T. rex and a rare felid

September 18, 2009 • 6:51 am

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.

8 thoughts on “Tiny T. rex and a rare felid

  1. Yikes! It seems as if Paul may have made the same mistake as the Darwinius group: they’ve let the new name out online and in newspapers prior to their publication of the name. Unlike the Darwinius group, they are planning to publish the name soon (in Science), but until then the name is not published, and they run the risk of the name being published by someone else, or the taxon being named something else by someone else, in the meantime. (For those not familiar with this aspect of the Darwinius debate, see here, and recall that posting something online does not constitute publication in systematic zoology.)

  2. One of the articles I read speculated that other groups of dinosaurs might contain so far unknown micro versions of their well known larger members.

    But a pint-sized predator with similar adaptations may make sense. Would a 6-foot long Apatosaurus make sense? Having a long neck to increase reach makes a lot more sense when you are up against a body size limitation. If you can afford to get, bigger, you just get bigger, it would seem to me.

  3. A new dinosaur, and the first color photograph of this cat, and only three comments so far? Here, let me help you guys out: I think the little T-rex-like species was really wholly without front limbs in life. But unfortunately, it swallowed a much smaller prey species, which thrust its front limbs through the dinosaurs lower throat. The rest of that hapless prey was fully swallowed and digested, leaving no trace of its presence in the little dinosaur. Then, after taking a dump, the little dinosaur at last perished from its wounds. Sometimes you see much the same thing happen in snakes today. It’s called the principle of uniformity. How’s that?

    1. Look Barry, my having to go through life with the multiple personality disorder form of schizophrenia is bad enough. But this having to clean up your internet nonsense has got to stop. And look at this one – it’s absurd! It’s just like that other poster said, you’re nothing but a representative of ignorance and arrogance. So just shut the hell up!

      1. Well excuse me Barry. I thought it might help generate more comments. Over at Pharyngula the comments on this dinosaur are all ready over a hundred (no insult intended), and there are all kinds of neat quips. As examples: it might eat coconuts, you could fit it better on Noah’s ark, use it for rodeos, you can pick up women easier if you walked one on a leash, feed it “feeder poodles”, there is an image of the Virgin Marry on top of the skull, and many more. Even PZ had a quip about a ride sign (for under 12 only). Now just how is my comment any worse? At least I tied mine to current events (the snake from China). Offered a hypothesis that, while admittedly extreme, is at least as reasonable as some of the stuff coming out of evolutionary psychology (and far more probable than the butterfly symbiosis stuff I would think). And I gave an excellent and easily recalled example of the principle of uniformity (if we see living predators with prey limbs sticking out of them today – the snake from China again – then we can reasonably expect that the same thing happened in the past). Oh, and it took a dump, so all trace of the prey evidence was gone – the paleontologists never knew. That’s the way I like to get points across. I mean what else can you really say if all you’ve seen is a reconstruction?

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