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RE: Genera belonging to Herrerasauridae
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
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
Protoavis, a chimaera of drepanosaurid, coelophysoid, pterosauromorph, and
who knows what else.