Dino-Feather Story Gets Fluffier
Xing Xu is at it again, claiming that dinosaur feathers are found everywhere – in China, at least, where the bulk of “feathered dinosaur” claims keep turning up in farmyards. The latest claim is that “Feather structures in maturing dinosaurs changed as they grew.” This story is accompanied by artwork showing the critters looking as big and fierce as dinosaur monsters (see PhysOrg and National Geographic); in reality, though, they would have been as small as pigeons.
Xu’s paper in Nature concerns two specimens of Similicaudipteryx, which is, obviously, similar to Caudipteryx. Yet Caudipteryx has long been considered by some as not a dinosaur but a member of the class Aves (birds) that became secondarily flightless (see 12/27/2000, 01/25/2008, 01/21/2009). Since none of the critics of dinosaur-to-bird evolution were allowed to rebut the claims of the paper in Nature, it is hard to have confidence this fossil has anything to say about a transition from dinosaurs to birds.
Xu claims that the plumage patterns seen in these few fossils “suggests that early feathers were developmentally more diverse than modern ones” and have no counterparts in modern birds. This is assuming that his team has correctly identified the fossils of extinct animals as members of the same species and can know their ages within acceptable margins of error without having living examples to observe. Even if that is true, the results do not provide any simple story for the evolution of feathers. Instead, it appears that modern birds’ moulting habits are simpler now than they were in the past.
1. Xing Xu, Xiaoting Zheng, Hailu You, Exceptional dinosaur fossils show ontogenetic development of early feathers,” Nature 464, 1338-1341 (29 April 2010) | doi:10.1038/nature08965.
The supplemental materials in Xu’s paper include a phylogenetic tree showing all the dinosaur groups that supposedly have feathers, and the feather types that have been found. At first glance it looks impressive, but a closer look raises questions. He has tyrannosaurids mixed in with the oviraptors and velociraptors and all these other animals. The cladogram supposedly shows ancestral relationships, with feather types at the tips of each group. You look at the feather types, though, and the clear bird feathers (pennate feathers with quills and barbs and barbules, and asymmetric flight feathers) have question marks by half the groups. You read the caption and find his disclaimer that the evidence is questionable for these. The ones that have the bird-like feathers could be said to be extinct bird lineages or secondarily flightless birds.
Xu tries to answer the argument that some of the feather-like structures might have been flayed collagen, but we need to see the counter-arguments from Feduccia and the guys at University of Oregon (02/09/2010). Nature, Science and National Geographic are giving way too much press to one side, to the Mr. Feathered Dinosaur guy Xing Xu. This is not good science. The whole story is not being heard.