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Jamie Stearns wrote-
As for the relationship between Ceratosaurus, coelophysoids, abelisauroids,
and tetanurans, I would say that while coelophysoids are probably a
paraphyletic group leading up to (neo)Ceratosauria/Tetanurae, abelisauroids
still can be grouped with Ceratosaurus, as osteoderms were found in both
Ceratosaurus and Carnotaurus, but not, to my knowledge, in any tetanuran
for which skin impressions are known.
There are no osteoderms known for Carnotaurus. The skin impressions do
include low conical protuberances, but there's no evidence these contained
bone. I believe similar protuberances are known for other large dinosaurs
such as hadrosaurs and ceratopsids, but lack any bony component.
As an aside, I don't agree with Sereno's revision of Tetanurae's definition,
adding Carnotaurus. As I wrote previously-
The addition of Carnotaurus as an external specifier by Sereno (2005) seems
counter-productive. Tetanurae was designed as a stem away from Ceratosaurus,
and abelisaurids were not explicitly discussed (having been named only a
year prior). In fact, technically, Indosaurus and Indosuchus were classified
as tetanurines by Gauthier (1986), since he lists them as carnosaurs. If
abelisaurids are megalosauroids (as in Paul, 1988), it shouldn't stop
megalosauroids from being tetanurines.