RE: Elaphrosaurus and Abelisaur Taxonomy

["Se$or Jonathan R. Wagner" <jrw6f@uva.pcmail.virginia.edu>]

Nick Pharris asked for ideas about the taxonomy of Elaphrosaurus and the
Abelisaurs (and some other critters I hadn't even heard of);

Elaphrosaurus:  Personally, my inexperienced eye questions Gregory Paul's
assignment of this genus to the ceolophyids.  I think he's right that it's
not an ornithomimid.  Tom Holz (apprently Tim's twin ;) ) recently called it
an "Ornithomimid-mimic".  Gadzooks, what a mouthful!  I'd be interested to
know if anyone has done a cladistic analysis which suggests this.  It sounds
as if the specimen is too fragmentary to really tell.

Abelisaurs:  Someone mentioned recently that some of Greg Paul's (no, he is
not my only reference!) Intertherapoda actually form a monophyletic clade.
     Discussion:
     1)  Torvosaurus (often placed at the next branching after Ceratosaurs
one the family cladogram) have hypershortened forearms, as does
Poikilopleuron (the humerus of which, as figured in _The Dinosauria_
(Weishampel et al.) seems to preclude congenericity, which Paul (oops, here
we go again) suggested in _PDW_ (Paul).  I do think he is on to something
with Torvosaurus and Megalosaurus, though.).  This is a trait associated with
Abelisaurs.
     (Incidentally:  In _Hunting Dinosaurs_, Jim Jensen calls Torvosaurus a
"big sauropod-killer", due to it's "large arms and big claws", good for
"ripping through the tough hides of sauropods" [paraphrased].  I don't see
how this is possible, considering it's really short forearms.
     2)  I'd like to know why Abelisaurs are placed in Ceratosauria.  They
seem superficially similar to Ceratosaurus itself, but not the more derived
Coelophysids.  They appear to have small pubic boots.  Then again, apparently
so does Ceratosaurus.
     One interesting character the process which devides the orbit between
the otic ring and the rest of the orbit formes a circle, and the center off
the otic ring is set behind the posterior edge of the (ill-defined) bottom of
the orbit.  This character seems to be present in Giganotosaurus as well.
     3)  Yangchuanosaurus seems too Allosauroid to be included.  I believe it
is currently listed in the Sinraptoridae, closest to the Allosaurs (look at
the maxillary process of the lacrimal).  It's Pubic boot is small, but it
appears to have a obpturator [sic?] process on the ischium.
     4)  Eustreptospondylus and Piatznykisaurus... pass
     5)  Sarcosaurus, inconclusive.
     6)  How Paul Sereno comes up with Spinosauridae + Torvosauridae is
beyond me.  He lists two characters for the clade (footnotes to the article
on Eoraptor), one of which is hyper-enlarged manual digit I ungual, which I
have never heard attributed to Torvosaurus.

     What I am guessing, and obviously this would have to be thoroughly
worked out, is what I believe Nick and Tom Holz came up with a few weeks ago,
a clade characterized by increasingly shortened forearms, no opdurator
process of the iscium (plesiomorphy), general absense of many tetanuran
characters, and a small pubic boot which seems (and I know seems...) to be of
equal size on both sides of the pubic shaft, and plesiomorhpic (downturned?)
femoral heads.  Not much to go on.  If it could be proven, I think it would
be appropriate to adopt Gregory Paul's terminology (sorry Mr. Paul), and
label this group Intertherapoda, sister to Avetheropoda.
     The big problem here is that most of these characters (except the arms)
are primitive to theropods, and it always seems that earlier Tetanurae were
very conservative of body plan, and I'm not sure there will be enough
evidence to ever prove or disprove early relationships amongst them.

     Oops, rambling again.
     Jonathan R. Wagner

---------------------------------------------------------------------------
     Jonathan R. Wagner
     Graduate student sanz portfolio
     jrw6f@uva.pcmail.virginia.edu