RE: eggshells, therizinosaurs & tyrannosaurs

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Ken Kinman
>
>      But so far, it sounds as though the "ornithoid" eggshell
> morphology is
> characteristic of primitive birds (including enantiornithines and living
> ratites) and the "non-avian" maniraptoran theropods (troodonts and
> oviraptors, and presumably dromaeosaurs by inference).

We do have to remember, though, that even within clades (such as Squamata or
Aves) you can get different shell structure morphology.

>      Since Therizinosaurs have the primitive dinosauroid eggshells, this
> seems to support Sereno's exclusion of that group from Maniraptora.  If
> Sereno is correct in placing tyrannosaurs as the immediate
> outgroup of the
> Maniraptora (sensu stricto),

You mean "sensu Sereno".  Maniraptora sensu stricto is "modern birds and all
taxa closer to modern birds than to Ornithomimidae": see Gauthier 1986.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-314-7843