paleonet Dinosaur Genera List corrections #168

[Dinogeorge@xxxxxxx]

There has been some discussion recently on the Dinosaur Mailing List about 
the classification of the Late Triassic Shuvosaurus inexpectatus, described 
by Sankar Chatterjee in 1993. Recall that he claimed it was a very early 
member of the group Ornithomimosauria, based on the striking similarities of 
the holotype skull to those of ornithomimosaurs. Subsequently, Murry & Long 
(1995) argued that Shuvosaurus was not dinosaurian but another kind of 
archosaur, and suggested that the skull represented cranial material of a 
taxon they named Chatterjeea elegans, based only on postcranial material. 
This seemed reasonable at the time, so I asterisked the genus Shuvosaurus in 
the Dinosaur Genera List as a non-dinosaurian archosaur.

Now it appears, from studies by Oliver Rauhut for his doctoral dissertation, 
that Shuvosaurus is a theropod after all. An email from Mickey Mortimer 
explained (edited a bit): "The only reason Shuvosaurus was removed from the 
Theropoda in the first place was because Long and Murry (1995) thought 
Chatterjee didn't prove it was a theropod.  They figured since no toothless 
Triassic theropods were known, it was more likely to be the head of the 
non-dinosaurian archosaur Chatterjeea, because like the non-dinosaurian 
archosaur Lotosaurus from China, Shuvosaurus lacked teeth. But Rauhut has 
proved Shuvosaurus is a theropod: ‘Shuvosaurus differs from rauisuchians and 
other basal crurotarsans in the following characters: loss of the 
postfrontal, paroccipital process directed ventro-laterally, lacrimal 
dorso-ventrally elongated, inverted L-shaped and exposed on the skull roof, 
presence of a deep basisphenoid recess, and ectopterygoid with expanded 
medial part and deep ventral fossa. All of these characters are found in 
theropods, and the latter three probably represent synapomorphies for this 
group (Gauthier 1986); therefore, Shuvosaurus can be referred to the 
Theropoda.' So get it back on that list. :-)"

This does it for me. I've removed the asterisk and notation and reinstated 
Shuvosaurus to dinosaurian status; always happy to have a prodigal dinosaur 
return. As to what kind of theropod it is, I have rather little idea, since 
we really need some postcranial material to help classify it. Perhaps 
Chatterjee's family Shuvosauridae really does belong in the Ornithomimosauria 
after all. If not, would that then make Shuvosaurus an ornithomimimimic?

(Actually, since Shuvosaurus is earliest, the ornithomimids were actually 
shuvosaurimimics, and extant ratites are the ornithomimimimics!)

Genera count remains stable at 916.

The well-organized Dinosaur Mailing List archive can now be visited directly 
from the Dinosaur Genera List. The link is in a short introductory paragraph 
I recently added about the history of the DGL.