RE: Genera belonging to Herrerasauridae

[Michael Mortimer <mickey_mortimer111@msn.com>]

Evangelos Giakoumatos wrote-

> The most recent publication I have access to, TDE, Supplement 3 (Glut, 
> 2003), indicates that Herrerasauridae is compirised of ?Agnostiphys, 
> Caseosaurus, Chindesaurus, Herrerasaurus, ?Spondylosoma, and 
> Staurikosaurus.

> How consistent is this account with current thinking? Should any of these 
> be excluded, or any other genera added?

The definition of Herrerasauridae is actually (Herrerasaurus + 
Staurikosaurus), so both Herrerasaurus and Staurikosaurus must be 
herrerasaurids.  This is agreed on by almost everyone, with one of the few 
dissenters being Kischlat (2001), who found Staurikosaurus to be a basal 
sauropodomorph.  However, the study this conclusion was based on is not yet 
published.  It is probably related to Kischlat and Barbarena's (1999) 
statement Staurikosaurus is only distantly related to Herrerasaurus, due in 
part to the lack of a trochanteric shelf.  If Staurikosaurus is a 
sauropodomorph, Herrerasauridae becomes the same as Saurischia or 
Eusaurischia (depending on where you place Herrerasaurus), and would 
probably be redefined.

Langer (2004) found Agnostiphys to resemble eusaurischians in the elongate 
postacetabular process, but to be outside Neotheropoda due to the 
semiperforate acetabulum and short preacetabular process. In addition, the 
astragalus has a deep elliptical slot for the tibial descending process, 
which is seen in Herrerasaurus and basal sauropodomorphs.  So it's more 
likely a eusaurischian, not a herrerasaurid.

Conveniently, I just wrote the Chindesaurus entry for my website (though it 
is not uploaded yet)-
Sereno (1999) found Chindesaurus to be the sister taxon of Staurikosaurus 
within Herrerasauridae, while Langer (2004) notes it has characters 
congruent with being a non-herrerasaurid herrerasaurian. Rauhut (2000) found 
it difficult to assign Chindesaurus to a less inclusive taxon than 
Dinosauriformes, though he agrees with Langer that the dorsals are less 
shortened than herrerasaurids. Furthermore, he finds the medially expanded 
brevis shelf resembles crurotarsans more than it does the laterally expanded 
brevis shelf of most dinosaurs. He believes the holotype may pertain to 
multiple individuals and/or taxa. Though originally a paratype of 
Chindesaurus, Hunt et al. (1998) made UMMP 8870 the holotype of a new taxon 
- Caseosaurus. This was based on the shallow brevis shelf, a more ventrally 
placed medial longitudinal ridge and a transversely thinner postacetabular 
blade. Langer (2004) has synonymized the taxa without comment.

Spondylosoma was reassigned to Crurotarsi by Galton (2000), though Langer 
(2004) noted the sacral rib character used was also found in herrerasaurids, 
and that another sacral rib character is more similar to the latter than to 
crurotarsans.  However, the deltopectoral crest is shorter than in 
dinosaurs.  So its placement seems uncertain, with either teratosaurid or 
herrerasaurid assignment being possible.

Other possible herrerasaurids include "Comanchesaurus", "Revueltoraptor" and 
other undescribed and unnamed specimens.

Taxa which have been referred to Herrerasauria in the past, but aren't 
currently thought to be, include-
Aliwalia, a junior synonym of the sauropod Eucnemesaurus.
Alwalkeria, a chimaera of probable eusaurischian and something else 
(crocodylomorph?).
Protoavis, a chimaera of drepanosaurid, coelophysoid, pterosauromorph, and 
who knows what else.

Mickey Mortimer