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Re: Tyrannosauridae (Spinosaurs, too)



At 09:36 AM 4/7/99 -0600, John M. Dollan wrote:
>One further question....

I think I can field this one... :-)

>The resource I am using

It would help if you mentioned that resource's name and authorship.

>has the Tyrannosauridae listed under Subdivision ARCTOMETATARSALIA (Holtz,
1994),

"Subdivision"?  No, it is a "Hyperclass".  (Hey, it's MY clade, so I get to
rank it!  And besides, the sister taxon is Maniraptora, a group which
explicitly includes the "Class" Aves, so Maniraptora has to be a "rank"
larger than Class.  And so its sister group (i.e., Arctometatarsalia) has to
an equal rank, so IT has to be bigger than a class.  And so...  I think you
see part of the problem of ranking here).

>which in turn is listed under Division MANIRAPTORA (Gauthier, 1986).  Is
this correct?

Well, kinda sorta.  In my 1994 phylogeny, I (improperly) redefined
Maniraptora to include the arctometatarsalians.  That was invalid, however,
so I have since (1996) proposed Maniraptoriformes to contain both
Maniraptora (birds and all taxa closer to birds than to _Ornithomimus_) and
Arctometatarsalia (_Ornithomimus_ and all taxa closer to _Ornithomimus_ than
to birds).  Incidentally, Maniraptoriformes is a "Transduperclass".

(For those keeping score at home, please note: Holtz is not a fan of
taxonomic "ranks").


>I had thought that the
>tyrannosaur family would be directly under the infraorder Tetanurae,
>along with the Megalosauridae and Allosauridae.

Ummmm..., I didn't fall through a worm hole or anything?  This IS 1999,
isn't it... :-)

Yes, well, the "Infraorder" Tetanurae (which explictly contains the "Class"
Aves!), DOES contain the megalosaurids, and the allosaurids, and the
tyrannosaurids, but it also contains ornithomimosaurs, and dromaeosaurids,
and birds, and whatnot.

However, if you are suggesting that tyrannosaurids are more closely related
to megalosaurids or allosaurids, then you (or your source) are at odds with
the concensus of just about anybody doing theropod systematics I can think
of: Currie, me, Novas, Gauthier, Sereno, Norell, Sues, Makovicky, Forster,
Perez-Moreno, etc..  The evidence indicates that tyrannosaurids shared a
more recent common ancestor with birds than with _Allosaurus_.  The
disagreement is whether tyrannosaurids were closer to birds than to
_Ornithomimus_ (Sereno), closer to _Ornithomimus_ than to birds (me, Currie,
Perez-Moreno et al.'s 1993 study), within Maniraptoriformes but unresolved
is closer to birds or to ornithomimosaurs (Gauthier's current stuff, Novas),
or outside the Maniraptoriformes (Norell, Sues, Makovicky, Forster,
Perez-Moreno in the _Pelecanimimus_ study).

So, yes, tyrannosaurids ARE tetanurines, and coelurosaurs.  If you want a
good workable non-committal type cladogram of tetanurines, you could go with
the one Gauthier used at the Chinese Feathered dino exhibit (although the
node names were not labeled), and is close to that in Dingus & Rowe and to
Novas' work:

Tetanurae
  "Torvosauria" (presumabely _Torvosaurus_, _Megalosaurus_, Spinosauridae, etc.)
  Avetheropoda/Neotetanurae (take your pick on the name)
    Allosauria (aka Carnosauria proper)
    _Sinosauropteryx_
    _Compsognathus_
    Coelurosauria
      Ornithomimosauria
      Tyrannosauridae
      Maniraptora
        Oviraptorosauria
        Paraves/Eumaniraptora
          Dromaeosauridae
          Avialae (aka birds)

>Gads, this can be confusing!!

Yeah, but it would be less confusing if you tried fitting the names to the
trees, rather than to the ranks.

Best bet for good cladograms of theropod relationships: Currie & Padian's
Encyclopedia of Dinosaurs; Dingus & Rowe's The Mistaken Extinction; or
Sereno's paper in the 1997 volume of Annual Review of Earth and Planetary
Sciences.  (Or Padian et al.'s paper in the latest JVP).

>In regards to creating a Linnaean list of all known dinos....

Don't.  (Sorry).

>Is there now a Spinosaur family (Spinosauridae)?

Ummm... yes, and there has been for awhile.  In fact, it has been a common
topic of discussion on this list since November of last year.

>If so, what members
>belong to it, aside from the obvious (Spinosaurus), and would the it be
>under the infraorder Tetanurae?  If not, where exactly would the family
>be placed?

Yes, they are tetanurines.

Members are _Spinosaurus_, _Baryonyx_, _Irritator_, _Angaturama_ (may be the
same animal as _Irritator_), _Suchomimus_, and other more fragmentary forms
(_Cristatusaurus_ being the only of these definitely a spinosaurid).  For
recent spinosaur papers, see Sereno et al.s 1998 paper in Science
282:1298-1302 and the accompanying perspective on pp. 1276-1277.

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