Saturday, February 23, 2008

Missing Link Feather Fossils

Make that three transitional fossils we have found this month.
(Click here to see the first and here to see the second).

Found Via Telegraph

As long as scientists have studied birds, they have puzzled over that most intricate of avian features - the feather.

Because it is a marvellous feat of biological engineering, it has been siezed on by creationists trying to find evidence of designs that lie beyond the abilities of evolution. Scientists themselves have squabbled over whether they first emerged to keep warm, to enable the first airborne creatures to fly from the ground, or so they could glide from bough to bough in trees.

The new fossils were found in a quarry in Charente-Maritime, western France, by Vincent Perrichot of Humboldt-Universität zu Berlin, with Dr Loïc Marion and Dr Didier Neraudeau of the University of Rennes, France. The designs display a flattened primary shaft which has branches, called barbs, which have not yet been fused by sub branches called barbules, marking a step towards the flattened shape of modern feathers.

With Dr Paul Tafforeau, from the European Synchrotron Radiation Facility, Grenoble, they conclude that structure represents "an intermediate and critical stage" in the evolution of feathers that had been predicted but was hitherto undocumented by evidence from the fossil record.

They report the work in the Proceedings of the Royal Society, Biological Sciences.

"What is very important in our discovery is that we have found a new clear example of the gradual trend of the evolution in general and in particular in the case of the transition between a primitive filamentous down and a modern feather," says Dr Neraudeau. "Moreover, it shows that in many cases, when an evolutionary stage is predicted by the theory, it can often be found in the fossil record. It is a question of time.

"Thus, it does not really change our picture of evolution but it gives for the first time a proof of the gradual evolution of feathers from the primitive filaments of some theropod dinosaurs to the modern feathers of Archaeopteryx and Cretaceous birds," he says.

Since these kinds of feathers occur in both early birds and some dinosaurs, the fossils could have come from either, though the site does contain the teeth of a known feathered dinosaur.

The widely accepted idea that birds evolved from dinosaurs is based on the idea that small, specialised theropod - two-legged - dinosaurs and carnivorous, bipedal dinosaurs with three-toed feet gained an advantage by growing feathers leading to three highly contentious theories.

First, that feathers developed from a novel protofeather, rather than scales; second, that they originated for retaining heat, with the implications that body heat was generated internally in reptiles; and third, that such feathers, primarily unconnected with flight, eventually enabled the ancestor of birds to fly from the ground up, defying gravity.

The alternative theory of the evolution of flight, bearing in mind that the structures associated with flight would have been very poorly developed at first, was that birds took to the trees for safety.

From there, it was a relatively small step to developing gliding skills and then the ability to fly.

The first known bird is Archaeopteryx, which lived around 150 million years ago.

Photos of the feathers:


David Morgan said...

A feather's a feather's a feather.

AIGBusted said...

Yes, these are feathers, but not modern ones. Read the article.

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500 years