A bizarre reptile with vane-like appendages sprouting from its spine may have been the ancestor of birds, according to a group of scientific mavericks. But researchers who believe that birds descended from dinosaurs dismiss the new claim.
Most paleontologists say there's no question about the origin of birds. They cite numerous skeletal similarities that link modern birds to a group of dinosaurs called the theropods. Despite this, a small group of ornithologists and paleontologists has long argued that certain differences, such as the identity of bones in the hand, mean that dinosaurs can't be birds' true ancestors. But they haven't had much luck finding an alternative.
Now these outsiders think they've got a strong candidate, a 220-million-year-old fossil called Longisquama insignis. The reptile was discovered decades ago in an ancient lakebed in what is now Kyrgyzstan. Paleontologist John Ruben of Oregon State University in Corvallis and graduate student Terry Jones first saw it in early 1999, as part of a privately sponsored fossil show. What riveted their attention was the creature's long, thin appendages--which they think bear a breathtaking resemblance to bird feathers. For example, they and other colleagues note in the 23 June issue of Science that the appendages have a central shaft with narrow ribs that extend out to the edges, roughly comparable to barbs on a feather. And near the spine, the shafts have wide, tubular bases, as do modern feathers. Ruben's team now touts the squat, mouse-sized fossil as "an ideal bird ancestor."
The minority of scientists who reject the dinosaurian origin of birds are elated by the new description of Longisquama. "It's almost too good to be true," says Storrs Olson, curator of birds at the Smithsonian Institution. But the evidence for feathers is marginal at best, says Rick Prum, curator of ornithology at the University of Kansas's Natural History Museum. Feathers tend to fray at the edges, he notes; Longisquama's plumes are fused. What they really look like, Prum believes, is ribbed membranes.