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Re: Caudipteryx not a bird and more from APP

Dora Smith wrote:

My understanding is that caudpteryx and some other close relatives of birds
are controversial as to whether they are birds.

I think that particularly controversy has dissipated over the past few years. There is strong (probably compelling) evidence that _Caudipteryx_ is not a bird, but an oviraptorosaur. Oviraptorosaurs are not currently considered birds (i.e., a member of the clade Avialae) - but this may change. Thus, currently, _Caudipteryx_ is not usually considered a bird, and its placement at the base of the Oviraptorosauria has strong support.

It is also sometimes
argued that they are evidence that archeopteryx are not birds' direct
ancestor but a dead end.

I'm not certain how _Caudipteryx_ could be brought into this argument, pro or con. The belief that _Archaeopteryx_ is not the DIRECT ancestor of modern birds comes from anatomical evidence (_Archaeopteryx_ has one or more derived characters that preclude it from being the avian ancestor) and chronological evidence (_Archaeopteryx_ lived too late in time to have given rise to the diversity of bird taxa we see in the Early Cretaceous). Personally, I don't regard either argument as especially compelling.

It would be really good to be able to do genetic studies to determine if all
modern birds are really descended from teh same lineage of dinosaurs - I see
real cause to wonder.

Most ornithologists and paleontologists would disagree. The morphological and molecular both overwhelmingly support the hypothesis that modern birds (Neornithes) are monophyletic.

More than one line of dinosaurs were evolving in birdlike directions.

I think it's more accurate to say that certain theropod lineages evolved bird-like traits independently (compare mononykines to ornithothoracine birds, for example), and one of these lineages became birds.

The notion of a polyphyletic Avialae has some supporters, as does the associated hypothesis that powered flight evolved TWICE in dinosaur evolution (I've heard Kurzanov's name associated with this). However, 99.9% of researchers regard the birds (Avialae) as monophyletic, and hold that flight evolved just once in dinosaurs.