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Re: Origin of feathers



On April 22nd, Jonathan wrote:

>>An interesting idea proposed last weekend at Dinofest by Mark Orsen is   
that feathers may have evolved for the purpose of brooding early on in   
the history of theropods. He used Oviraptor as an example.  If you've   
seen the most recent fossil of O. sitting on it's nest, you can see it is   
trying to cover its eggs to protect them from the presumably scorching   
heat of the Mongolian desert. <<

I would have taken a quote from a recent posting by Dr. Orsen's co-author   
of the paper proposing wing feathers for Oviraptor, but I deleted his   
e-mail by accident. Jonathan's comment started this discussion, however,   
and he raised the issue equally as well.

Incubation and brooding are distinctly different phases in the parental   
care of eggs and chicks.  And I think that distinction is critical in   
assessing Dr. Orsen's (et al) speculations about Oviraptor. Webster's   
dictionary, for example, defines incubation as the use of heat (usually   
body heat) to bring about embryonic development in eggs, while brooding   
is defined as the care of young birds. Under those definitions, the use   
of the term "brooding" to describe the behavior of Oviraptor is   
inappropriate, since only eggs were found in the nest. This is not just   
semantics. It means that the authors are asking us to accept the use of   
one behavior in modern birds to support the presence of a entirely   
different behavior in an extinct animal that is not a bird. It seems a   
bit of stretch to use the analogy of modern birds that use their wings to   
assist in brooding chicks to infer 1) that Oviraptor's arms were   
feathered and 2) that it used those wing feathers to incubate its eggs.

Intuitively I like the idea of a feathered Oviraptor, for a number of   
reasons; and the feathers really do seem to "fit" quite well in the   
illustration I've seen. But I can't buy it on the arguments I've heard so   
far. I've even searched the literature and talked to a couple   
ornithologists in a futile effort to find an example of a modern bird   
that uses its wing feathers to incubate eggs. No luck. If Oviraptor   
really was a "wing incubator", it was exhibiting an apparently novel   
behavior.