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Re: Coelurosaurs (was segnosaurs)



In a message dated 96-03-01 20:40:09 EST, Thomas_R_HOLTZ@umail.umd.edu (th81)
writes:

<<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.>>

These formal definitions and such are all well and good, I suppose, but we
should always keep in mind that the ICZN (International Commission on
Zoological Nomenclature) does not govern taxonomic categories at levels
higher than those with the term "family" in their names (i.e., superfamily,
family, subfamily; and for that matter, it doesn't address such terms as
gigafamily, megafamily, hyperfamily, etc., either). There is as yet no
consensus within the group (that I know of) about how to deal with the
multitude of names and levels that cladistic taxonomies have presented us
with, so using a term like "formally defined" for such groups seems a bit
inappropriate. It carries an aura of officiality that is in reality still
absent.

There was a time when Carnosauria was defined in such a way as to include
_Tyrannosaurus_ as well as _Allosaurus_, but we are now pretty sure that that
definition gave us a polyphyletic group. So that particular definition of
Carnosauria is no longer acceptable. In the future, it may turn out that
_Allosaurus_ is related to birds in a different way from what we now think,
which could likewise render the above "formal definition" of Carnosauria
meaningless.