characters of Monolophosaurus

[jconrad@lib.drury.edu]

> Subject: characters of Monolophosaurus
> 
> Sorry, everyone for taking so long to list these characters.  Thanks to
all
> who replied.
> 
> First off, it has been mentioned by Currie and Zhao (1993) and reported in
> Glut (1997) that the supposed horn of _Proceratosaurus_ may be a midline
> crest.  This is what got me to looking at _Monolophosaurus_ illustrations
> and photos.  It has been suggested that the anterodorsal portion of the
> premaxilla makes up part of the possible nasal horn in _Ornitholestes_ and
> possibly the crest in _Proceratosaurus_.  This is also the case in
> _Monolophosaurus_.  The morphology of the anterior part of the maxilla is
> more similar in the three aforementioned taxa than any is to the
carnosaurs
> with a shallow, squared off anterior portion which then flares dorsally
> behind the naris.  Then ventral margin of the maxilla is straight or flat
in
> all three.  In allosauroids, the quadratojugal forms "good" L shape with
the
> ascending process facing upward, but in _Ornitholestes_ and
> _Monolophosaurus_ it seems to angle rostrally.  Also in _Ornitholestes_,
> _Monolophosaurus_, tyrannosauroids, and _Dromiceiomimus_ and some other
> ornithomimids the quadratojugal has a broad contact with the squamosal. 
In
> carnosaurs, this contact is relatively narrow or, at best, along a nearly
> vertical anterior-posterior slope.  
> 
> Of course, the twin obturator processes seem similar to carnosaurs and the
> preacetabular process of the ilium is seems  similar in gross morphology
to
> that of carnosaurs.  I don't pretend to be an expert on this issue, but I
> feel that the position of _Monolophosaurus_ as basal carnosaur or
> allosauroid should at least be questioned.  
> 
> Thanks for your time, have a great night!
> 
> Jack
> 
> ------- End of forwarded message -------