Theory of Birds\' Evolution under fire by Fred Bervoets
We now question very strongly whether there were any feathered dinosaurs at all.\" Professor John Ruben, of Oregon State University.
Scientist think that the small lizard-like unusual archosaur from the Late Triassic of central Asia called Longisquama insignis is the oldest known feathered animal. The fossils in question were excavated in 1969 in Kyrgyzstan, a former Soviet republic.
When the impressions now said to be feathers were first identified as reptilian scales, the specimen was put away in a drawer in Moscow and ignored. But they were retrieved and displayed as part of a touring exhibit of Russian fossils last year.
Along its dorsal axis Longisquama bore a series of paired integumentary appendages that resembled avian feathers in many details, especially in the anatomy of the basal region. The latter is sufficiently similar to the calamus of modern feathers that each probably represents the culmination of virtually identical morphogenetic processes.
According to the scientist Longisquama insignis probably glided among the trees 75 million years before the earliest known bird and they say this challenges the widely held theory that birds evolved from dinosaurs. Their statement re-ignited the debate about the evolution of birds by seriously questioning whether they evolved from dinosaurs. Longisquama insignis, had elongated structures on its back and arms that look very much like the feathers of modern birds.
This suggests an evolutionary link between the two. But the scientists say, Longisquama was not a dinosaur, and they argue that it is unlikely that features as complex and specialised as feathers evolved more than once. Stone impressions showse, its elongated back appendages had hollow shafts and other characteristics closely resembling those of feathers.
Professor John Ruben, of Oregon State University and one of the scientists investigating Longisquama said: \"These are some amazing fossils, and at the very least they prove that feathers did not evolve in dinosaurs, the supposed link between dinosaurs and birds is pretty entrenched in palaeontology, but it\'s not as solid as the public has been led to believe.\" He added: \"Feathers are a very complicated structure. The odds of them evolving first in Longisquama and then separately at some later point in dinosaurs or any other group of animals would have been astronomically small.\"
Terry D. Jones, a member of the discovery team and the lead author of a report published in the journal Science said: \"We can identify certain structures in these fossils that you only find in feathers, so we\'re quite sure we\'re looking at the earliest feather.\"
But beyond that, this animal looks like an ancestral bird even if you ignore the feathers. The teeth, pectoral structure, neck, and skull are just like those of birds.
The researchers think the feathers evolved for flight rather than insulation. Providing warmth is the more likely function of the downy feathers sported by some much later dinosaurs. Longisquama probably glided, rather than flew, using its long aerodynamic forelimbs for steering.
Dr Alan Feduccia, a co-author from the University of North Carolina at Chapel Hill, who in 1979 proved for the first time that Archeopteryx, the earliest recognisable bird, could fly, said: \"These are the earliest structures in the fossil record that can be called feathers.\" Prior to this, the oldest feather belonged to archaeopteryx, also recognized as the earliest bird.
Archaeopteryx lived about 145 million years ago, and its fossils were found in Germany in the 19th century. He also said: \"They pre-date the so-called \'fuzzy dinosaurs\' from China by at least 100 million years.
Here we show unequivocally that the earliest known feathers evolved in the context of flight and not thermo-regulation.\"
The analyzed fossils of Longisquama shows the animal had a wishbone virtually identical to archaeopteryx and similar to modern birds. According to the scientist the feathers are nonavian and the exact relationship of Longisquama to birds is uncertain.
The fossil evidence does not conclusively establish that Longisquama was an ancestor of flying birds, John A. Ruben of Oregon State said, it would have lived in the right time and had the right physical structure to have been an ancestor. It seems that feather evolution extended back much earlier, probably before the first dinosaurs appeared on the scene about 240 million years ago.
\"A point that too many people always ignored is that the most birdlike of the dinosaurs, such as bambiraptor and velociraptor, lived 70 million years after the earliest bird, archaeopteryx,\" Dr. Ruben said in a university statement. \"So you have birds flying before the evolution of the first birdlike dinosaurs. We now question very strongly whether there were any feathered dinosaurs at all.\"
Former analysis of George Olshevsky, showed that Longisquama is the sister group of all other theropods and birds within Dinosauria and is thus, cladistically speaking, a dinosaur. It is the most primitive-known dinosaur with a furcula, the next most primitive is Protoavis.
George Olshevsky doesn\'t know why the researchers of Longisquama do so desperately want dinosaurs to be unrelated to birds. He noted: \" Unfortunately, these workers overlooked or discarded without consideration the very real possibility that Longisquama is itself a very primitive small theropod, not merely an archosaur _ belonging to the sister group of herrerasaurian and more advanced theropods. \"