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Re: Ankylosaurs, Stegosaurs, and other fun things..



----- Original Message -----
From: "Steve Brusatte" <dinoland@lycos.com>
To: <dinosaur@usc.edu>
Sent: Wednesday, July 03, 2002 3:53 AM
Subject: Re: Ankylosaurs, Stegosaurs, and other fun things..


> Marginocephalia is now (at least as of Sereno's 2001 paper in _The Age of
Dinosaurs in Russia and >Mongolia_) united by three synapomorphies:
parietosquamosal shelf extension obscuring the occiput in >dorsal view,
median contact between the maxillae that excludes the premaxillae from the
anterior margin of the >external nares, and a short postpubic process
lacking the distal pubic symphysis.  But, the first character was
>criticized, and in _The Dinosauria_, Dodson and Currie found the second to
be pleisomorphic.  The third >synapomorphy was similarly criticized, but
better outgroup comparisons have strengthened it.

In view of the fact that there're great evidence that Heterodontosaurids are
basal Marginocephalia perhaps it is time to redefine the synapomorphies that
uniting Marginocephalia, perhaps we can added the presence of a diastema
between the premaxillary and maxillary teeth, the presence of three
premaxillary teeth, etc..etc..

By
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Alessandro Marisa
Via Achille Grandi n°18
Rovereto (TN) ITALY
Tel: 039-0464-434658 Email: amaris@tin.it
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