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From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of StephanPickering@cs.com>"Carnosauria" is paraphyletic, and should not be used.Certainly "Carnosauria" as used circa 1990 is paraphyletic. However, this taxon has been restricted more recently to the clade comprised of Allosaurus (the only taxon which has been in every incarnation of Carnosauria) and taxa sharing a more recent common ancestor with it than with modern birds.>Megalosaurus = Torvosaurus (on the basis of the extensive, thoroughly described/illustrated hypodigm of the>former I am about to publish, the latter cannot be separated from Megalosaurus Buckland 1824).Has your research involved extensive examination of the substantial new material, much of it unpublished, belonging to Torvosaurus (split by some workers into two or more genera)? Although I strongly suspect (as first noted by Greg Paul) that these two taxa are phylogenetically very close, there are still distinguishable.>Proceratosaurus is NOT a ceratosaur, but shares interesting similarities to Ornitholestes, being in my book>Maniraptoriformes incertae sedis.These two taxa are most certainly coelurosaurs (Holtz 2000), may well be maniraptoriforms (see Holtz 2001), and may indeed be sister taxa (also Holtz 2001).>Ceratosauria may yet prove to be paraphyletic,Or at least the batch of taxa in the Ceratosauria chapter of The Dinosauria may yet prove to be paraphyletic. The taxon Ceratosauria has been defined (Rowe 1989) as Ceratosaurus and all taxa sharing a more recent common ancestor with it than with Aves, and is thus consequently monophyletic.> Liliensternus + Dilophosaurus + Walkersaurus hesperis being more closely related to each other than>to Coelophysis/Syntarsus, Merosaurus newmani, Sarcosaurus, Elaphrosaurus.Although this arrangement is indeed possible, it is also possible that you are grouping the former cluster on size-based characters or primitive features rather than on shared novelties. Rauhut (in press) has the most extensive examination of the coelophysoid type theropods I know of in press, althought Tykowski is also doing some major rehaul of these taxa (as might someone else).Elaphrosaurus remains problematic, having some very coelophysoid-like features but also some abelisauroid-like features.>Ceratosaurus needs to be subjected to a thorough, robust cladistic analysis.As it indeed has been, on several occasions. However, new specimens have come to light (several unpublished, but shown at SVP meetings), and (perhaps not so curiously) those researchers who have examined these specimens and worked on theropod phylogeny now find that true ceratosaurs (comprised of Ceratosaurus and abelisauroids) are closer to Tetanurae than are the coelophysoids...
Thomas R. Holtz,
Jr.
Vertebrate
Paleontologist
Department of Geology
Director, Earth, Life & Time
Program
University of Maryland
College Park
Scholars
College Park, MD
20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:
301-405-4084 Email: tholtz@geol.umd.edu
Fax
(Geol): 301-314-9661 Fax (CPS-ELT):
301-405-0796