Natural Science Forum / Biology / Paleontology / October 2005

http://www.cbsnews.com/stories/2005/10/10/tech/main931079.shtml

AP) 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.

"The question is, which three? In dinosaurs we know it's the thumb and the
next two fingers," he said, something experts call the "1-2-3" morphology.
But the study's third author, Dr. Richard Hinchliffe -- a recognized expert
in vertebrate limb development -- "points out that there are five different
assessments showing that the bird hand has the three middle fingers left,"
the "2-3-4" morphology, Feduccia said.

All of this suggests that dinosaurs never had feathers, he said, and that
birds evolved on a separate track from dinosaurs, although the two may have
shared a common, distant ancestor.

Not everyone agrees. Back at the American Museum of Natural History,
another paleontologist said Feduccia's bird theory may just be a wild goose
chase.

"I don't agree with their argument," said Xing Xu, the museum's resident
expert on avian evolution. First of all, he said, looking at the recently
decayed remains of a modern animal tells us little about how dinosaur
protofeathers might or might not have been preserved in stone tens of
millions of years ago.

And, he said, the samples of collagenous filaments Feduccia's team presents
as an alternate explanation for protofeathers don't match those seen in the
fossil record. "In the paper, these fibers are 0.2, 0.5 millimeters long,"
Xu said. "That's much tinier than the ones we have in the feathered
dinosaurs like Sinosauropteryx which are 2, 3 even 5 centimeters long
sometimes."

The orientation of Sinosauropteryx's protofeathers also runs perpendicular
to the animal's long bones, whereas collagenous fibers from modern animals
run roughly parallel to these bones. "It's another problem," Xu said.

John M. Rensberger, former curator of paleontology at the Burke Museum at
the University of Washington, Seattle, called Feduccia's paper "the best
presentation" he's seen yet of the argument that birds did not descend from
theropods. But he agreed with Xu that Feduccia's theory has flaws.
Regarding alleged differences in bird and theropod hand morphology, both he
and Wu said scientists are still debating whether birds display the 1-2-3
digit arrangement or the 2-3-4. "It really hasn't been proven one way or
the other," he said.

And he said his own research as a specialist in morphology favors the
birds-came-from-dinosaurs theory. "All the bones that I've looked at of the
more lightly built theropods are indistinguishable @1/8in internal
structure @3/8 from those of birds," Rensberger said. "And that's a
completely unique situation among all vertebrates. It's a strong indication
of a very close relationship between birds and theropods."

But Feduccia contends his own evidence is equally strong.

"I think all this takes us back to the drawing board -- we have to start
re-looking at where birds come from," he said.

He also believes media and museum hype over "feathered dinosaurs" has done
paleontology a disservice.

"There's been way too much hyperbole. To get back to any good science
you've got to get away from that and get back to the bench," Feduccia said.
"I think the field is ripe for some young scientist who doesn't have any
cemented views to come in and look at this and paint it with a brand-new
brush."