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Re: Evidence For a Feathered Velociraptor...



----- Original Message ----- From: "Dora Smith" <villandra@austin.rr.com>
Sent: Sunday, September 23, 2007 4:19 PM


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.

If you haven't seen research, that doesn't mean it doesn't exist! :-)

All known Cenozoic birds share a number of unique weirdnesses, for example -- off the top of my head! -- 15-upwards sacral vertebrae, a bony bridge over a tendon at the foot end of the shinbone, a complete lack of teeth (that's not unique, but it's unique compared to the close relative *Ichthyornis*), and probably dozens of others that must be hidden in huge studies like the recent one by Livezey & Zusi.

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.

But...

- wouldn't that amount of convergence be a bit improbable?

- if it were so, how could we ever find out?

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

Of course not. But molecular characters are not necessary for phylogenetics. Morphological ones work, too... it's just more work to find them.