Re: Rauhut's Thesis

["Mickey Mortimer" <Mickey_Mortimer11@msn.com>]

Jaime A. Headden wrote-

>   Aside from so ceratosaurian vertebrae, *Sarcosaurus woodi* is
> identified from a partial left pelvis with dorsally convex
> ilium, fused elements, and overall similarity to *Ceratosaurus*
> itself. I would suggest, but without coding it yet, that it is a
> true ceratosaurid exclusive of dilophosaurs, abelisaurs,
> coelophysids, etc...

Actually, Rauhut does consider Sarcosaurus' phylogenetic position.  He could
only code a few characters, so it was included in his analysis.  He does
comment that the strong downward bend at the acetabulum differentiates it
from other Early Jurassic theropods except Dilophosaurus.  He thinks that
there are no morphological differences between the two genera, but the much
larger size of juvenile Dilophosaurus shows it was a separate taxon.  I
disagree that they are identical, as Dilophosaurus has- deeper preacetabular
process (1.2 times preacetabular length versus 1.09), closing gap between it
and pubic peduncle; distinct convexity on distal end of pubic peduncle; more
overhanging supracetabular crest, obscuring dorsal acetabular edge in
lateral view; concave posterior postacetabular edge; posterodorsal process
on corner of postacetabular process; no obturator notch in pubis.  These are
almost all apomorphies of Dilophosaurus, so don't help much with
Sarcosaurus' relationships.  The convex dorsal ilial edge could be a
synapomorphy of a Dilophosauridae including Sarcosaurus.  I think the ilial
blade is much more similar to Dilophosaurus, but the peduncles and
acetabular area is closer to Ceratosaurus.

Mickey Mortimer