Re: Monolophosaurus

[TWILLIAMS@canr1.cag.uconn.edu]

> 
> I was just wondering if anyone out there has seriously questioned the
> placement of _Monolophosaurus_ as basal Carnosauria. I feel like it is
> possibly basal Coelurosauria.  I would be happy to discuss this with
> anyone, on or offlist, if there is any interest.  


I'm not so sure it is basal Carnosauria.  Before I go on I think it's 
worth mentioning that "Carnosauria" means different things to 
different people.  As I understand the term, the "Carnosauria" is 
a paraphyletic assemblage of non-coelurosaurian tetanurines 
(megalosaurids, allosauroids, maybe spinosauroids).  Others regard 
the Carnosauria as a valid clade - the monophyletic sister-group to 
the Coelurosauria (and the basal clade of the Avetheropoda) including 
only the allosauroids and maybe a few closely related genera.

Confused?  It gets worse.  I believe the original description of 
_Monololophosaurus_ regarded it as a "megalosaur-grade" theropod - 
essentially a basal tetanurine or basal "carnosaur".  But subsequent 
revisions (sorry, don't have the papers handy) have moved 
_Monolophosaurus_ further up the tree and put it somewhere among the 
Allosauroidea.  Under this scheme, the Allosauroidea is the sister-
group to the Coelurosauria.

The thing is, the line between derived "carnosaurs" and primitive 
"coelurosaurs" is a little blurred.  Look at the carnosaur-like 
features of _Ornitholestes_ - Greg Paul (in _PDW_) even regarded 
_Ornitholestes_ as an allosaurid.  Future cladistic analyses could 
push other "carnosaurs" - like _Baryonyx_, _Proceratosaurus_ and 
_Gasosaurus_ - into the Coelurosauria.  


Tim