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Re: Evidence For a Feathered Velociraptor...



Yup, I know there's been alot of discussion about bird phylogeny. To my knowledge none of it has considered whether all modern birds or even all birds that survived the end Cretaceous extinction were descended from the same lineage of dinosaurs. It seems as if every feathered dinosaur that survived the end Cretaceous extinction is automatically a bird, and is automatically descended from just one line of dinosaurs, which is probablistically doubtful.

What I'm saying is that if a number of lines of dinosaurs were structured exactly like birds and were fully flighted, this supports the idea that modern birds may not all be of one lineage. If just one line of dinosaurs developed flight, then logically everything that survived the end-Cretaceous extinction is descended from them, regardless of whether it flew, had teeth, was six feet tall, hunted, and did not fly, and had teeth, or any number of other large differences between big classes of "birds" living after the end Cretaceous extinction.

Genetic studies that put crocodiles as the outgroup do not prove that all modern birds are descended from a single line of dinosaurs.

Yours,
Dora Smith
Austin, TX
tiggernut24@yahoo.com
----- Original Message ----- From: "T. Michael Keesey" <keesey@gmail.com>
To: "Dinosaur Mailing List" <dinosaur@usc.edu>
Sent: Saturday, September 22, 2007 8:24 PM
Subject: Re: Evidence For a Feathered Velociraptor...



On 9/22/07, Paula Goodman <paulawilder@mac.com> wrote:
That's something I was wondering too --- like could the ratites be more
closely related to secondarily flightless dinosaurs... than to a bird
that had lost (or re-lost?)  flight later.

This has been pretty adequately studied. Ratites are much closer to other modern birds (especially tinamous) than to extinct flightless lineages such as _Deinonychosauria_. They share a number of apomorphies with other modern birds that are not seen in _Deinonychosauria_, many of which are also not seen in _Confuciusornithidae_, _Enantiornithes_, _Hesperornithes_, _Ichthyornithidae_, etc. (each one being closer to crown group avians than the one before it).

In other words, it is extremely, extremely unlikely that crown group
_Aves_ includes deinonychosaurs.

--
T. Michael Keesey
Director of Technology
Exopolis, Inc.
2894 Rowena Avenue Ste. B
Los Angeles, California 90039
http://exopolis.com/
--
http://tmkeesey.net/




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