Re: Diagnoses

[<twilliams@canr1.cag.uconn.edu>]

> I'm also confused about the
> Bullatosauria, Spinosauridae & Irritator mess. 

Makes two of us.  In their original description of _Irritator_, Kellner and 
friends shoehorned _Irritator_ into the Bullatosauria (Troodontidae and 
Ornithomimosauria), but this assignment (by the authors' own 
admission) was precarious. 

Other authors (informally I believe - I haven't seen anything published) think
_Irritator_ may be more comfortable in the Spinosauria.  The conical 
teeth and long snout with the nares moved far back from the tip are 
characters reminiscent of _Spinosaurus_ and _Baryonyx_.  Postcranial 
elements would help to place _Irritator_, but if wishes were horses ...

< Where does Archaeornithoides fit; 

The specimen is tiny (<30mm) and probably from a juvenile (even a
neonate or embryo).  _Archaeornithoides_ was regarded by Elzanowski and
Wellnhofer (1992) as an avian-relative; more specifically, a link between birds 
and spinosaurids.  The authors also allied _Archaeornithoides_ closely with 
a critter named _Lisboasaurus_.  However, _Lisboasaurus_ was then regarded as
a mini-maniraptoran, but has since been re-interpreted as a 
crocodilian!  In general, subsequent authors have tended not to take 
E and W's ideas on theropod phylogeny on board.

Considering the presumed ontogenetic stage of the _Archaeornithoides_ specimen, 
the 
jaw material may be of negligible phylogenetic value.  (Is it true that the 
specimen
was originally regarded as a coming from an embryo tarbosaur?)

Tim Williams

>