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New _Ceratosaurus_ paper
Nick Pharris wrote (quite a while back):
Um, exsqueeze me? What the heck is _Ceratosaurus magnicornis_?
Date? Provenance? How securely is it differentiated from _C. nasicornis_?
The paper is:
Madsen Jr., J.H. and Welles, S.P. , 2000. Ceratosaurus (Dinosauria,
Theropoda), a revised osteology. Utah Geological Survey Miscellaneous
Publications (MP-00-2): 80 p.
I just received a copy, and not bad for $12. And it's for a good cause.
They describe two new species of _Ceratosaurus_ from the Morrison Formation.
The first, _C. magnicornis_, is differentiated from _C. nasicornis_ by
proportional differences in the skull, vertebrae, and limb bones. It
appears to be a more robust species compared to _C. nasicornis_. The nasal
horn is longer, but lower than that of _C. nasicornis_, and the lacrimal
"horns" are better developed.
I suspect though that future studies on _Ceratosaurus_ may sink _C.
magnicornis_ as a junior synonym of _C. nasicornis_. After reading Smith's
study (in JVP) of _Allosaurus_ specimens from North America, it is possible
that the differences between _C. magnicornis_ and _C. nasicornis_ might be
explained by intraspecific variation within a single _Ceratosaurus_ species.
_Coelophysis bauri_ and _Dilophosaurus wetherilli_ also show a lot of
morphological variation among the specimens referred to each species.
_C. dentisulcatus_ is the second new _Ceratosaurus_ species named by
Madsen and Welles. C. dentisulcatus_ appears to be more distinct from _C.
nasicornis_ than _C. magnicornis_ is. It gets its species name by the
distinct grooves (sulci) running down the length of the anterior teeth of
the upper jaw. _C. dentisulcatus_ also has fewer maxillary and dentary
teeth, and the front of the dentary is strongly curved and upturned. There
are also proportional differences in the elements of the skull (such as a
lower snout) and postcranium compared to the two other N. American _Cerato_
species. The nasals and lacrimals are not preserved in _C. dentisulcatus_
so its "horns" (assuming it had them) cannot be compared with the other two
Finally, I think that the medium-sized, rectangular-shaped premaxilla from
the Cleveland-Lloyd Quarry that was referred to _Stokesosaurus clevelandi_
may actually belong to a young _Ceratosaurus_.
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