Re: Eoraptor question

["Thomas R. Holtz, Jr." <th81@umail.umd.edu>]

Since there was some discussion earlier about _Eoraptor_, herrerasaurid, and
neotheropod (Ceratosauria + Tetanurae) relationships, here are some of the
data from the as yet unpublished (but working on it!!) Holtz & Padian study:

Characters found in these forms, as well as sauropodomorphs &/or
ornithischians are not listed below.
More importantly, the characters found in ornithischians and (esp.)
sauropomorphs which are found in neotheropods but NOT in _Eoraptor_ and/or
herrerasaurids are not listed below. They are, however, numerous.

Characters shared by _Eoraptor_, Herrerasauridae, and Neotheropoda:
Transition point in tail
Manual digit V reduced to a vestige or absent
Manual digit IV reduced

Characters found in Herrerasauridae and Neotheropoda:
Manual digit IV ungual absent
Intramandibular joint (however, the geometry of this joint is different in
herrerasaurids and neotheropods, as discussed in Sereno and Novas' 1993
study of the skull of _Herrerasaurus_)
Second intercentrum large and concave for reception of first intercentrum
Elongate zygapophyses present on distal quarter of tail
Caudal cervical epipophyses elongate

Characters found in _Eoraptor_ and Neotheropoda:
Reduced contact between premaxilla and maxilla
Distal carpal V absent
Reduced overlap of dentary onto postdentary bones
Pubic blade greater than six times as long as broad

Incidentally, the reduction of the size of digit IV is greater in _Eoraptor_
and herrerasaurids than that found in Ceratosauria, and comparable to the
basal tetanurine position.


Hope this helps.

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