Re: STRANGE THEROPOD SKULLS

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

Let's leave the ischium subject alone for now: the characters given 
belong to dinos that are largely incomplete and require better material 
to work with in several cases. This needs to be researched more 
thouroughly, and I'll see this in a while. Not very soon, though.

<<The femora of most "carnosaurs" I listed are diagnostic are all mostly 
strait, have a raised fourth trochanter near to the epiphysis, a large 
medially or forward-set lesser trochanter, and a raised femora head. A 
few lack some of these characters (e.g., *Gasosaurus*) and these almost 
all occur in the Jurassic, with the most advanced (or derived) forms 
appearing in the Cretaceous (carcharodontosaurs, Afro, spinosaurs and 
dryptosaurs).>>

<Since when are dryptrosaurs carnosaurs?>

I didn't say that. If Afro is a torvosaur and therefore outside of 
Carnosauria, one can include dryptosaurs and spinosaurs as possible 
filtering tools as well. Add "megalosaurs" to that, _all_ of which at 
one time or another were regarded as carnosaurs. But I do not believe 
this is true. Using an example of a basal tetanurine/coelurosaur.

<The femur is also susceptible to functional change (such as from 
migration of the M. caudofemoralis or any other muscles that can be 
adapted for a special locomotion).>

Granted. Oviraptorid femora are very close in morphology to troodontid 
femora, but that does not make oviraptorids bizarred troodontids. It 
does make them related, however. Braincases even better, but that was 
another thread.

<<Good point, Paul.>>

<I'm not Paul, I'm Matt.>

Got you confused. I meant you, however.

<<<In what features? Crylophosaurus may be lacking one or two allosaur 
features, but that does not mean a close relationship.>>>

<<But Cryo does occur earlier than most other carnosaurs, and has 
features both primitive and those considered "carnosaurian"; pneumatic 
lachrymals without lachrymal foramen, a combo of primitive and 
carnosaurian. The pelvis was described, but not figured, and I don't 
know if the photos of the specimen show it, since I haven't seen them. 
Glut (1997) cites Hammer and Hickerson (1994) in saying the femoral head 
declines from the greater trochanter, where the opposite is diagnostic 
for carnosaurs, the extensor groove on the back of the femur is shallow, 
and both characters are diagnostic for coelophysoids; there is a fusion 
of the ankle bones resulting in a tibiotarsus, indicative of 
neoceratosaurs. The posterior ramus of the angular extends to the rear 
of the mandible, with the ventral process of the surangular invading the 
angular's lateral surface, creating a "bulge" that is seen only in 
sinraptorids. The orbit is invaded dorsally by processes from both the 
lachrymal and postorbital. Otherwise, other characters of the skull can 
be either neoceratosaurian or "megalosaurian">>

<Crylophosaurus does show a mix of primitive and advanced features as 
correctly shown, but other carnosaurs show other primitive features 
(such as a camerate bone structure in Marshosaurus) that are indicative 
of a more basal standing than Crylophosaurus.>

Greater basality? How? Cryo occurs in the Pliensbachian (or even 
earlier) while the next basal "carnosaurs" (*Gasosaurus* or 
*Kaijiangosaurus*, who occur earlier than a less controversial dino, 
*Piatnitzkysaurus*) come from the Bathonian, yet Cryo is given priority; 
more definite is *Monolophosaurus*, and he's from less detirminate beds 
(mid J, according to Glut 1997 and _Encyclopedia of Dinosaurs_).

<Crylophosaurus shows features that ally it with the Allosauroidea that 
are lacking in more basal carnosaurs.>

There are features lacking in Cryo that Mono, Piat, Marsho, and a few 
others share.

<<This dinosaur seems to represent one of the best examples of a 
transistory taxon, truly between one group and the other.>>

<So its a basal tetanuran now?>

It shows characters of both sides. It can be on either side of a line 
that needs real definition in my mind. No insult to Tom Holtz, of 
course, but the two most persistant characters for carnosaurian 
morphology are an inclided femoral head and a lachrymal foramen, both of 
which Cryo lacks.

<<<Ugh! Afrovenator is a torvosaur, related to spinosaurs. It lacks all 
allosaur apomorphies. Carcharodontosaurs and sinraptorids are closely 
related.>>>

<<That Torvo may be a carnosaur could make this problematic.>>

<How is Torvosaurus a carnosaur?>

The same way Cryo could be a carnosaur, with a few characters here, and 
a few there, add in a apomorphic character, and _voila!_ a wierd dino!

<<And I guess I must be a stubborn cuss, but I hold to Afro's 
carnosaurian nature. The lachrymal foramen is lacking in Torvo and 
Meggie, the tooth is flat laterally and thus bladelike in a form that is 
nearly identical to allosaurs (and even carcharodontosaurs, though not 
"wrinkled" or evenly serrated). The pubis is double-curved as in 
Eustrepto (another possible torvosaur) and *Neovenator*. There is a 
maxillary fenestra, nasal participation in the antorbital fossa 
[assumed: no nasals known]. The cnemic process of the tibia is 
ceratosaurian, though, and unusual for a Cretaceous (Barremian- 
Hauterivian?) dino unless it were a Neoceratosaur (which torvosaurs may 
be). Form of humerus is allosaurian.>>

<<I don't think that these features hold weight.>>

Since these characters cross several lines, as do Torvo, Meggie, and 
Cryo, I'll have to agree. For all we know, this character on/off-ishness 
may be the one defining character in these guys! :-)

<Since I have not yet seen Neovenator I'll not mention it.>

Wise choice. Somewhere on the net is a website on the Isle of Wight 
which features an article on Neo including a brief description, story, 
and sillhouette of the skeleton. In _Dinosaurs, the Encyclopedia_ (Glut, 
1997) the cast and mounted skeleton of *Neovenator salerii* is pictured 
in the *Megalosaurus* entry, but this doesn't show many of the features 
I listed but for a good 3/4-shot of the skull which will help me a 
little.

<But Afrovenator shows more synapomorphies with torvosaurs than it does 
with allosaurs.>

_These_ I'd like to see, just as a filter to counter-filter my supposed 
carnosaur one. I'd really like to have the Afro debate resolved.

If it's one thing these threads have taught me on carnosaurs, it's not 
to play too much with them. These dinosaurs and their closest kin (at 
least that's a relationship not too controversial) are so 
morphologically like chameleons that I feel you have to get to the 
nitty-gritty and just wait until each has a complete skeleton waiting, 
and the Kimmeridgian and Barriasian-Valanginian gaps are filled. It's 
about time I stepped off this thread.

Jaime A. Headden

"But, if I must...."

(P.S., Sorry about the mix-up, Matt, it was unintentional.)

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