Definitions of Ornithomimosauria

[Thomas_R_HOLTZ@umail.umd.edu (th81)]

Nino wrote:

>Since I diagnose the clade Ornithomimosauria in the _Pelecanimimus_ paper,
>and there is anode in the cladogram with this name, I think
>Ornithomimosauria has been cladistically defined. That is, _Pelecanimimus_
>and all taxa sharing a more recent ancestor with _Pelecanimimus_ than with
>_Troodon_ (at least until my future work on the phylogeny of
>Ornithomimosauria will be finished).

I would STRONGLY urge you to use _Ornithomimus_ rather than _Pelecanimimus_,
so that (by definition) Ornithomimosauria will always include
_Ornithomimus_.  (Gauthier's 1986 definition of "Ornithosuchia" did not use
_Ornithosuchus_, so that now _Ornithosuchus_ is not an ornithosuchian... :-( )

I would agree that the two definitions would describe the same clade, given
what we know.  If, however, it turns out that (strange as it might seem)
_Pelecanimimus_ might have a more recent common ancestor with _Troodon_ than
with _Ornithomimus_, we would be stuck with _Ornithomimus_ outside of
Ornithomimosauria.  I don't expect anyone will find this particular
three-taxon statement, but I'd like the phylogenetic taxonomic definitions
to be as "bomb-proof" (to use a computer programmer's term) as possible.

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661

"There are some who call me...  Tim."
-- Tim the Enchanter, "Monty Python and the Holy Grail"
---------- subtitle --[Monty Python ik den Holy Grailen]

"Tim?!?  They called me TIM?!?!"
-- Tom the Paleontologist, on seeing "The Ultimate Guide to T. rex" :-)