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Coelurosaurs (was segnosaurs)



>
>> What about the phylogeny of the Segnosauria?  Have the segnosaurians,
>> like the tyrannosaurians, now been classified in the Coelurosauria?
>>
>> Tim Williams
>
>       I find the notion of the Coelurosauria a bit dated nowadays,
>since reading Paul's PDW.  personally think they were a group somewhere
>near the ancestral ornitho/sauris split. Mos people that think of the
>predatory dinosaurs as big carnosaurs, or small coelurosaurs tend to
>overlook creatures like Nanotyrannus, and creatures like Dilophosaurus
>(more akin to Coelophysis).

Perhaps I might interest you in a couple of readings on the subject of the
new revamped Coelurosauria?  Gauthier's 1986 paper on the origin of birds
and my 1994 paper on the origin of tyrannosaurs, as well as a couple of
other influential papers by Sereno et al., Dong and Russell, Perez-Moreno et
al., Fernando Novas, Currie, etc.  have transformed our knowledge of
coelurosaurians and restored it closer to the original.

When Friedrich von Huene named "Coelurosauria" and "Carnosauria", he quickly
recognized that some large theropods were more closely related to certain
small forms than they were to Allosaurus and Megalosaurus, the "type"
carnosaurs.  In particular, Huene allied tyrannosaurids with ornithomimids,
and Ceratosaurus with Coelophysis.

Only through the influence of North American orthogeneticists such as H.F.
Osborn did "carnosaur" and "coelurosaur" come to mean "big theropod" and
"small theropod", respectively.

Gauthier has transformed "Coelurosauria" into its current form:  birds and
all theropods more closely related to birds than to carnosaurs.
(Carnosaurs, incidentally, are being formally defined as Allosaurus and all
theropods closer to Allosaurus than to birds).  Tyrannosaurids are back in
Coelurosauria, where they always belonged.  Ceratosaurus and Coelophysis are
neither carnosaurs nor coelurosaurs, but are either part of their own
radiation (Ceratosauria) or progressively more distant relatives of the
carnosaur-coelurosaur group.

Hope this helps.  For more info, check Gauthier 1986 (Bull. California
Academy of Sciences, isn't it? Not in my office right now, so I can't check)
and Holtz 1994 (Journal of Paleontology 64: 1100-1117).

Thomas R. Holtz, Jr.
Vertebrate Paleontologist     Webpage: http://www.geol.umd.edu
Dept. of Geology              Email:th81@umail.umd.edu
University of Maryland        Phone:301-405-4084
College Park, MD  20742       Fax:  301-314-9661