[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Caudipteryx not a bird and more from APP
----- Original Message -----
From: +ACI-Dora Smith+ACI- +ADw-villandra+AEA-austin.rr.com+AD4-
Sent: Friday, February 04, 2005 1:58 AM
+AD4- I know that birds are thought to be monophylatic. Now, in the time when
+AD4- they evolved that would have included a pretty big group of animals.
At their time of origin, this included one species (or +AF8-part of+AF8- a species).
Otherwise they wouldn't be monophyletic.
+AD4- They were already so diverse in the Cretaceous, that I don't think that
+AD4- proven they all evolved from a single common ancestor among the dinosaurs
+AD4- that we know of.
Don't lose sight of the enormous amounts of time involved. +ACo-Confuciusornis+ACo-
lived some 25 million years after +ACo-Archaeopteryx+ACo-. That's a lot of time. For
example, 25 Ma before now there were (almost?) no grasslands anywhere on
+AD4- I can see how the skeletons of birds differ from thsoe of their cousins -
+AD4- but multiple lines of therapods were evolving in similar ways because
+AD4- ways constituted strong adaptive advantages. I am not saying that birds
+AD4- did NOT evolve from a single line, but I'm not convinced it's proven.
In part this depends on what you mean by +ACI-birds+ACI-. The living birds are
monophyletic beyond any reasonable doubt. So are the short-tailed birds, I'd
say. I'd be a bit more careful with including the long-tailed birds
(+ACo-Archaeopteryx+ACo-, +ACo-Rahonavis+ACo-, +ACo-Shenzhouraptor+ACo-, and perhaps
Scansoriopterygidae) -- but even there there's no good published evidence
that they evolved from a different group than the short-tailed ones (for
example, the long-tailed ones have been suggested to be closer to
dromaeosaurs and the short-tailed ones closer to oviraptorosaurs +-