Dinosaur Flap Ruffles Feathers

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Head to the American Museum of Natural History's Web site, and you'll see the major draw this fall is a splashy exhibit on dinosaurs.

And not just any dinosaurs, but two-legged carnivorous, feathered "theropods" like the 30-inch-tall Bambiraptor -- somewhat less cuddly than its namesake.

The heyday of the theropods, which included scaly terrors like T. rex and velociraptor, stretched from the late Triassic (220 million years ago) to the late Cretaceous (65 million years ago) periods.

But most authorities on dinosaurs will tell you these creatures' direct descendents strut, screech and squawk among us today -- as birds.

In fact, an entry on theropods from the Web site of the University of California, Berkeley's Museum of Paleontology attests that "recent studies have conclusively shown that birds are actually the descendants of small, non-flying theropods."

However, a study in the October issue of the Journal of Morphology suggests that theory may be, well, for the birds.

Based on evidence ranging from a buried dolphin to differences in a three-fingered hand, the study suggests birds are not the smaller, chirping descents of T. rex's kin, after all.

"Thing just aren't adding up for feathered dinosaurs," said lead researcher, avian evolutionist and paleobiologist Alan Feduccia of the University of North Carolina, Chapel Hill. He described the prevailing theory that birds descended from theropods as paleontological "wish-fulfillment" based on "sloppy science."

Instead, said Feduccia, birds and dinosaurs may be related, but only by a common ancestor stretching back hundreds of millions of years.

The new study first attacks the notion that the reptile fossil record is rife with feathers or what paleontologists call "protofeathers" -- long, filament-like structures observed in fossils like that of the 150-million-year-old Archaeopteryx. In 1996, scientists in China discovered an even more striking, allegedly "feathered" fossil, Sinosauropteryx.

"It had these little filament-like structures all over it, especially on the back and tail," Feduccia said. He said that because the dinosaurs-begat-birds theory is now "accepted dogma," paleontologists automatically declared these filaments to be feathers without doing the necessary research to back that claim up.

"The whole thing had become circular -- birds are dinosaurs, so whatever we find on dinosaurs that looks like a rudimentary feather has got to represent the origin of feathers," Feduccia said.

But he and his colleagues have long thought otherwise. Instead, they counter that these filaments are the fossilized remains of "collagenous fiber meshworks" lying under the dinosaur's skin. To help prove that theory, co-researcher Dr. Theagarten Lingham-Soliar buried a dolphin for one year, then exhumed it and looked at the patterns of decay.

"The fiber-collagen meshwork looked virtually identical to these so-called 'proto-feathers' found in the Chinese dinosaurs," Feduccia said.

The researchers also produced examples of fossils with similar, feather-like markings from another dinosaur, Psittacosaurus. Trouble is, all paleontologists agree that this large non-therapod is in no way a bird ancestor.

Finally, Feduccia's team also contends that the forearm of a small "bird-like" theropod with the avian name of Pelicanimimus was actually covered in scales, not feathers.

Then there's another piece of evidence: the bone structure of the modern bird foot.

Feduccia explained that most primitive vertebrate hand structures were like that of humans: five-fingered. Somewhere in the evolutionary process, both dinosaurs and birds lost two of those digits, leaving three behind.

  • David Hancock

    David Hancock is a home page editor for CBSNews.com.