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Re: Theropods with avian characters






> I am trying to make up a short list of theropods which have been described
> as either having characters in common with avians and not shared by common
> or garden theropods, or having characters intermediate between 'non-avian'
> theropods and avians (such as the quadrate articulation in _Troodon_)
> 
> I have _Troodon_, _Avimimis_ and _Saurornithoides_. Any others?
> 
> Chris> 
> 
> 
It is hard to define what a "garden variety" theropod is. As Aves is 
nested well within the Theropoda there are number of increasingly 
exclusive clades which aquire more bird like characters as you head 
towards this group. Tetanurans (including Torvosaurus, 
Baryonyx, Allosaurus, Ornitholestes, Tyrranosaurs, Dromaeosaurs and birds 
to name but a few) share  bird like features such as  loss of 4th manual 
digit and development of a semi-lunar carpal with a  transverse trochlea 
(Sereno,1994) which are not seen in ceratosaurs (Coelophysis, 
Ceratosaurus, Abelisaurus etc.). However the most bird like of the 
theropods that dont actually belong in Aves are the non-avian members of
 Maniraptora. This clade includes the genera you mentioned as well as
 Dromaeosaurids, Oviraptorosaurs, Mononykus (which may actually be a bird) 
and if you believe Tom Holtz's cladogram it also contains Ornitholestes, 
Tyrranosaurs and Ornithomimosaurs.

Adam Yates