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Re: pelicanomimus



>From: tholtz@geochange.er.usgs.gov
> > I wrote:
> > >
> > >That's not *quite* correct, but I tend to agree that this is too
> > >many teeth for it to be a proper ornithomimid.
> > >
> > >In that case, it would be in the Coelurosauria (restricted sense)
> > >or in the basal Maniraptora.  ...
> > 
> > But it will be much better in September :-) (see reference 23 in the
> > Pelecanimimus paper)
> > 
> > Anyway, we can do better than that.  Pelecanimimus shares, uniquely with
> > the Ornithomimidae, metacarpals of all the same length and proportions of
> > the phalanges of the hand.  In this respect it is more similar to valid
> > ornithomimids than to Harpymimus. 
>
>Ah, this is important.  Assuming for now that this is a valid
>synapomorphy, not a convergence, it forbids placing Pelecanimimus
>is a stem group ("Coelurosauria") AND Harpymimus in Ornithomimosauria.
>[That would make either the "stem" group or the ornithomimosaurs
>polyphyletic, which no biologist will accept].

What the hell are you talking about?  It does nothing of the sort.  A whole
range of synapomorphies place ornithomimosaurs in Coelurosauria (see
Gauthier) and additional characters show that Ornithomimosauria is a member
of the coelurosaurian subgroup Maniraptora (the aforementioned ref. 23). 
Thus, Pel. & Harpy. are ornithomimosaurs AND maniraptorans AND
coelurosaurs.  The hand of ornithomimosaurs are thus transformed from the
basal maniraptoran condition.  Given the structure of the hand of
Harpymimus (which retains a primitively short mc I), it would appear that
the hand of Pelecanimimus is either convergent with Ornithomimidae, or that
Harpymimus represents an outgroup to the Ornithomimidae-Pelecanimimus
clade.

>
> >  Also, it shares with all
> > ornithomimosaurians and all troodontids the bulbous parasphenoid capsule
> > (an unusual structure of the braincase).  Therefore, the body of evidence
> > shows that this animal is a member of the troodont-ornithomimosaurian clade
> > (to be named in ref. 23), and additionally is closer to ornithomimids than
> > to troodonts.  Thus, it is an ornithomimosaurian.
>
>This seems right given what you said above.
>
>[And the alternative, *if* the similarities to the ornithimimosaurs
>are convergent, and only under that situation, is to place it
>in the same group as the Troodontidae - but this seems unlikely].

On this we agree.

                                     

                                
Thomas R. Holtz, Jr.
Vertebrate Paleontologist in Exile
U.S. Geological Survey
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092

email:  tholtz@geochange.er.usgs.gov 
Phone:  703-648-5280
FAX:            703-648-5420