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Re: Noasaurids (Re: Late Triassic Footprints with Reversed Hallux)



Michael Keesey wrote-

> I was just tying to think of groups with aberrant feet. Maybe it's a
> misperception, but it seems to me that theropod pedes are pretty uniform
except
> for noasaurids and certain coelurosaurs.

Just because noasaurids have antiarctometatarsalian metatarsi and
hyperextendable second digits doesn't mean they have a greater chance of
having a reflexed hallux.  The characters aren't correlated.

Steve Brusatte wrote-

> Yeah, I don't recall Coria assigning _Quilmesaurus_ to the abelisaur
lineage.  IIRC, he described it as
> unusual and exhibited some features that link it with _Ceratosaurus_,
_Giganotosaurus_, and some
> other forms.

I found Coria's quick dismissal of a ceratosaurian affinity for Quilmesaurus
based on the lack of tibioastragalar fusion premature and misleading.  The
holotype of Elaphrosaurus was mature and lacked this fusion, as do some
large specimens of Coelophysis.  In contrast, the absence of a well
developed incisura tibialis places Quilmesaurus outside Tetanurae.
Abelisauroids (eg. Velocisaurus, Elaphrosaurus) and coelurosaurs lack a
prominent anterior ridge on the distal tibia to brace the ascending process,
which is similar to Quilmesaurus.  And the hypertrophied cnemial crest is of
course characteristic of abelisaurs (eg. Genusaurus, Majungatholus), but not
plesiomorphic for theropods (quite the opposite in fact).  So I feel the
evidence for Quilmesaurus being an abelisauroid is quite good.

> It's a rather unique dinosaur, being so primitive yet being found so late
in the Cretaceous of France.
> When you say it is a "ceratosaur with features similar to basal
abelisaurs," are you perhaps indicating > that it might indeed turn out to
be a bona fide abelisaur?  That would be very interesting...and would
> only confound the temporal and geographical situation.

The problem with Genusaurus is that its describers realized it was a
ceratosaur, but not that abelisaurids were ceratosaurs.  So they never made
the connection of Genusaurus with abelisaurids.  As abelisaurids are common
in Late Cretaceous deposits, Genusaurus is not uniquely primitive for its
time.  Nor would its identification as an abelisaur be unheard of
geographically, as Betasuchus, Tarascosaurus and unnamed French (Buffetaut,
1989) and Spanish (Astibia et al., 1990) material are known from Europe.

Mickey Mortimer