The dinosaur-bird evolutionary link is widely recognized among paleontology circles as a strong paleontological theory. In other words, most every dinosaur paleontologist accepts the fact that sometime during the Jurassic period a small, carnivorous, theropod dinosaur evolved into the first bird. Their case has been aided by the discovery of several feathered dinosaurs in China during the later half of the past decade, but that doesn't mean that they don't have their detractors.
In the June 23, 2000 edition of the journal Science a team consisting of Terry Jones, Larry Martin, Alan Feduccia, Willem Hillennius, and John Ruben announced their findings on an enigmatic Triassic reptile named Longisquama insignis, a small creature that likely glided among the tree tops when the dinosaurs were just beginning to dominate. According to their paper, Longisquama squashes the popular dinosaur-bird link, but their theory has caused much debate among paleontologists.
Longisquama lived in Central Asia some 220 million years ago, placing it near the end of the Triassic Period and about at the time when some of the earliest known dinosaurs, Herrerasaurus and Eoraptor among them, were beginning to dominate the earth. The small, gliding reptile had four legs and several appendages protruding from its spine. When the animal was first discovered in the 1960's, the paleontologists naming it intrepreted these appendages to be scales, hence the name Longisquama ("long scale."). But, according to the new study, these appendages are feathers, making Longisquama the earliest known feathered animal known, easily topping the 150 million year old Archaeopteryx.
But, after its initial discovery in 1969 the lone Longisquama specimen was banished to a drawer in a Moscow institution. Then, in the late 90's it became part of a traveling Russian dinosaur exhibit. This exhibit passed through a Kansas City shopping mall in 1998, and one of the men present to view it was paleoornithologist Dr. Larry Martin. Upon viewing the specimen Martin decided to solicit the help of paleoornithologist and known dinosaur-bird detractor Dr. Alan Feduccia, the author of a controversial book on avian origins. Feduccia was struck by the shaft of these appendages, covered by a sheath, a characteristic of bird feathers. Furthermore, Feduccia and Martin inferred that Longisquama's 'feathers' would have been adequate for gliding, but the animal's musculature was not capable of sustaining flight. Given more time, the team reasoned, the muscles could have developed and the feathers could have spread to the forearms, creating wings.
But, in their paper the Feduccia/Martin/Jones team only described the feathers, shying away from presenting an avian evolutionary line extending from Longisquama. Instead they included the simple statement, "the exact relationsip of Longisquama to birds is uncertain." But, in an Oregon State University Press release, the university that employs Ruben, Ruben stated, "Longisquama would have lived in the right time and had the right physical structure to have been an ancestor -- and it was clearly not a dinosaur." This angered several pro-dinosaur-bird evolutionists, including Dr. John Horner, who stated, "this is bad science. I can't believe this was published. They didn't even present an evolutionary history extending from Longisquama."
The lack of an evolutionary lineage from Longisquama was not the only evidence the pro-evolutionists had to offer. According to several paleontologists, the 'feathers' on Longisquama may simply be folds of skin, likely used for gliding. Others claim that the 'feathers' are acutally ferns fossilized along with the Longisquama skeleton. Still others say that the 'feathers' are simply skin flaps like those seen on moths. In fact, two of North America's most renowned paleontologists, Dr. Chris Brochu of the Field Museum of Natural History in Chicago and Dr. Hans Dieter Sues of the Royal Ontario Museum have studied the specimen and believe that the appendages are absolutely not feathers, or nothing even close to them.
Even if Longisquama did possess feathers, Dr. Mark Norell of the American Museum of Natural History reasons, that doesn't mean that Longisquama is an evolutionary ancestor to modern birds. Norell points out that the feathered dinosaurs of China actually lived after the first true birds developed. In other words, possibly these 'feathers' on Longisquama evolved independently of the avian lineage for other reasons, possibly for insulation or sexual display.
The debate on this small creature will likely continue as long as Feduccia, Martin, Ruben and their small clan of anti-dinosaur-bird evolutionists publish papers knocking the dinosaur-bird link. But, their detractors say, the dinosaur lineage of birds will remain the most acceptable theory as long as the small group of outspoken paleontologists continue to skirt around a non-dinosaur avian evolutionary lineage.
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