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Fragilis vs. atrox

Here's a question:

_Allosaurus fragilis_ and/or _Allosaurus atrox_?

Same species or two different species?

"Predatory Dinosaurs of the World" shows them as the latter with some very different cranial features. I've also seen written references citing the two species names as interchangeable.

Just trying to verify.


--Kevin Hedgpeth


From: Dinogeorge@aol.com
Reply-To: Dinogeorge@aol.com
To: amaris@tin.it, dinosaur@usc.edu, th81@umail.umd.edu
Subject: Re: R: Late J Heterodontosaurs (was Re: Sereno's Prosauropoda)
Date: Thu, 8 Jul 1999 18:39:47 EDT

In a message dated 7/8/99 4:55:04 PM EST, amaris@tin.it writes:

<< For me the Heterodontosauridae is closer to Marginocephalia than to
 Euornithopoda, infact the three caniniform teeth are present only in the
 Marginocephalia (Protoceratopsidae and Pachycephalosauria) and not in
 Euornithopoda. >>

This is best apomorphy uniting H and M. But there are a few problems, such as
premax extanding back to lacrimal in Heterodontosaurus and many (though not
all) advanced ornithopods (probably appeared independently in
Heterodontosaurus). Also a nice suite of primitive features common to H and
M, but these aren't phylogenetically interesting. 


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