Re: Torvosaurus

["Jaime Headden" <jaemei@hotmail.com>]

I wrote:

<<Can anyone tell me if they agree that the similarity of *Torvosaurus'* 
and *Cryolophosaurus'* lachrymals means that Torvo can be included in 
the Carnosauria as on the same cladistic branch of *Cryolophosaurus* and 
basal Allosauroidea?>>

<Could be, but what does the weight of the evidence say? Single 
character resemblances are interesting, but one must figure out a) are 
the resemblances derived or primitive and b) what is the distribution of 
other features in the anatomy.>

*Sinraptor* has an otherwise unspectacular lachrymal, when compared to 
*Allosaurus* and *Yangchuanosaurus*. I refer to the flange at the base, 
very long and occlusive of the jugal from the antorbital fenestra. Such 
a flange is seen in *Allosaurus*, *Yangchuanosaurus*, and to a less 
occlusive state, *Monolophosaurus*. It appears the same condition [long 
flange] is evident in *Acrocanthosaurus*, though the jugal appears to be 
incomplete in the photo I've seen of the skull (right side).

This may be synapomorphic, though my case is not very strong. 
*Ceratosaurus* has an occluded jugal, but the lachrymal flange is very 
short, and neither the skulls of other "megalosaurs" like *Edmarka* or 
*Megalosaurus* seem to possess the bone.

All add something, though. The dentary tooth of the type of 
*Megalosaurus* is less strongly curved (very strait, indeed) than 
*Torvosaurus'* is, and the curve is similar enough to *Yangchuanosaurus* 
and *Allosaurus* that it supports a carnosaur-link. And besides, wasn't 
Torvo already plausibly connected to the Carnosauria, at least as an 
outgroup?

<The skull of Cryolophosaurus is pretty puzzling as currently described, 
particularly the squamosal-postorbital-jugal contact (which, in all 
right-thinking theropods, do NOT form a single contact in the middle of 
the infratemporal fenestra!!). I haven't seen the postcranial material, 
so that's (obviously) more difficult to judge...>

That's a shame---many similarities I've noted between currently 
recognized taxa within Carnosauria are found on the pelvis. The humerus 
of the *Torvosaurus*, though, does have some similarities with 
*Allosaurus*, and *Afrovenator*'s forearm is also somewhat similar.

It _IS_ a most interesting skull, and I've just finished restoring it on 
paper, and will soon scan it in to my computer, along with a redraw of 
the *Monolophosaurus* skull from Zhao & Currie, 1993.

<In most recent studies, true carnosaurs (Allosauroidea and closely 
related forms) are more closely related to coelurosaurs than either 
group is to Torvosaurus. Carnosaurs and coelurosaurs share a maxillary 
fenestra, pneumatic lacrimals, and other features not known in 
Torvosaurus.>

These may be derived features; but I agree that these are some of the 
prime characters detrimental to my hypothesis. Still would like to see 
the postcrania . . . My library's shut down for a week, so I can't get 
to some materials, but can you tell me if the October 1994 National 
Geographic issue's article on the frozen carnosaur has any photos? I 
also heard a Sunday Chicago Times article had published photos of the 
skeleton and skull.

<However, it is possible that later studies might reveal features 
uniting allosauroids and Torvosaurus within Carnosauria. Such is the way 
of phylogenetic analysis (or any science, for that matter: subject to 
revision based on new data).

I think that Bakker et al.'s and Sereno's suggestion that 
Eustreptospondylus is closely related to Torvosaurus may have some merit 
based on current data. Unfortunately, both are less complete than one 
(okay, I) would like... :-(>

This idea I concur with, as my clades you've seen show, with 
*Eustreptospondylus* as very basal (and probably the progenitor) of the 
Carnosauria . . . and not only is he incomplete, but juvenile. My only 
problem is that *Gasosaurus* and *Kaijiangosaurus* may be more 
primitive, as the Dashanpu has not been accurately dated, as far as I've 
read in _Encyclopedia of Dinosaurs_ and _PDW_ and other texts.

Jaime A. Headden

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com