Restating the obvious

Yesterday a short notice was printed in the journal Science describing where Tyrannosaurus fell in relation to birds on the basis of molecular evidence (i.e. proteins recovered from a Tyrannosaurus femur). Surprise, surprise, the study found that Tyrannosaurus is more closely related to birds than the American alligator or the green anole lizard. Not everything came out perfectly, however. The phylogenetic tree created by the molecular data but Tyrannosaurus in the same group as the birds, meaning that (in the words of the authors) it "leaves Dinosauria unresolved."

An even more obvious error involved the placement of the anole, the tree placing it as a sister group to mammals and archosaurs. Mistakes like this have brought the utility of such molecular studies into question, and as Thomas Holtz commented in a New Scientist article about the research "I could do a hell of a lot better with bones." Sure, it is really cool that protein gathered from preserved collagen from a Tyrannosaurus has been recovered and the extremely ancient proteins can still yield results that approximate what was already known from morphology, but I would have liked to have seen something a little more complete and rigorous than what was printed in Science.

Even if the study suffered some problems, however, it did support the fact that Tyrannosaurus and birds are more closely related to each other than either is to crocodylians. The problem is that the results can easily be misconstrued by mass media outlets, making it look like Tyrannosaurus was the ancestor of birds! The New Scientist article, for instance, is titled "T. rex confirmed as great granddaddy of all birds." NO! Even though it used to be grouped with other large predatory dinosaurs like Allosaurus, we now know that Tyrannosaurus was a huge coelurosaur, the group coelurosauria containing tyrannosaurs, ornithomimosaurs, and maniraptors, birds being contained within the maniraptora. This makes Tyrannosaurus an evolutionary cousin that shared a common ancestor with the group of dinosaurs that evolved into birds, not that it was a bird ancestor itself.

[Update: The title of the New Scientist article has now been changed, see the comment below.]

The body of the article is a tiny bit better, saying "Tyrannosaurus rex, meet the chicken - your third cousin more than 100 million years removed," but the real relationship between Tyrannosaurus and birds (as well as the true ancestors of birds) is not mentioned at all. This is frustrating to those who know better, but it also shortchanges people who aren't familiar with the present state of the science. When I was first trying to educate myself about what dinosaurs had to do with the origins of birds, popular news reports usually confused more than they helped, making it seem like dinosaurs like Velociraptor were the ancestors of birds rather than being creatures that helped confirm that birds are derived maniraptoran dinosaurs. If popular press articles aren't going to provide the proper context, confusion among the public and non-specialists will likely continue.

From what I understand more studies of the proteins recovered from the Tyrannosaurus collagen are planned, although we'll all have to wait and see what the nature of those studies are. In terms of evolutionary relationships, though, the new Science report is a drop in the bucket that compliments the flood of fossil evidence that confirms that birds are living dinosaurs.

References;

Organ, C.L., Schweitzer, M.H., Zheng, W., Freimark, L.M., Cantley, L.C., Asara, J.M. (2008). Molecular Phylogenetics of Mastodon and Tyrannosaurus rex. Science, 320(5875), 499-499. DOI: 10.1126/science.1154284