Re: no feathers on Pelicanimimus

[NJPharris@aol.com]

In a message dated 97-06-13 03:28:06 EDT, longrich@phoenix.Princeton.EDU
(Nick Longrich) writes:

>  On Wed, 11 Jun 1997 NJPharris@aol.com wrote:
>  
>  > In a message dated 97-06-10 12:41:32 EDT, longrich@phoenix.Princeton.EDU
>  > (Nick Longrich) writes:
>  > 
>  > > there is some indirect evidence that the common ancestor of
>  > >  troodonts, dromaeosaurs, and oviraptors did have honest to goodness
>  > >  avian-style feathers. 
>  > 
>  > Of course, this animal would also be the ancestor of tyrannosaurs,
>  > ornithomimosaurs, _Unenlagia_, _Archaeopteryx_, alvarezsaurs, true
birds,
>  > probably therizinosaurs, and a whole host of beasties no one has ever 
> heard
>  > of yet!
>  > 
>  > Nick Pharris
>  > 
>  Norell puts Troodon in the Maniraptora. 

Yes.  This seems to be a residual effect of the (IMHO outmoded) idea that
troodonts and dromaeosaurs form a monophyletic Deinonychosauria.


>  Tyrannosaurs and
>  Ornithomimids lack some birdlike specializations to arms, legs and tail
>  that are shared by the troodontidae with dromaeosaurs, oviraptoridae,
>  and alvarezsaurs and so these two would have to have a lot of reversals.

The most significant of these would, I assume, be 

1)loss of the semilunate carpal block in a general reduction of the wrist
(semilunate carpal blocks are reportedly present even in allosaurs, so the
lack of this character in any coelurosaur would be a reversal);

2)relengthening of the ischiadic rod;

3)loss of raptorial 2d digit on foot (also in oviraptorosaurs, alvarezsaurs,
modern birds);

I wouldn't call this *a lot* of reversals (I'm not sure what characters in
the tail you're referring to); on the other hand, dromaeosaurs, alvarezsaurs,
and oviraptorids lack many characters shared by troodonts, ornithomimosaurs,
and tyrannosaurs, including arctomet feet and D-sectioned premaxillary teeth,
which I count as carrying more weight.


>       -Nick L. 

-Nick P.