RE: TOROSAURUS/TRICERATOPS FRILLS

["Andy Farke" <andyfarke@hotmail.com>]

Here's a reply to several messages, all lumped together here.

<I was wondering if there is any possibility of _Triceratops_,
_Brachyceratops_, and _Avaceratops_ being related based on the solid
frill. I realize that the remains are fairly poor for the latter two.>

Brachyceratops and Avaceratops are closely related, but neither of those 
are closely related to Triceratops. Brachyceratops and Avaceratops are 
members of the Centrosaurinae, the more primitive subfamily of the 
Ceratopsidae. There is some debate over whether or not the frill of 
Avaceratops was solid, but I have seen the type specimen for it, and if 
there were fenestrae they were dang small.

My opinion, backed up by many characters, is that Triceratops and 
Avaceratops independently lost their parietal fenestrae. Based on other 
characters in the skull, it seems that Triceratops is more closely 
related to Chasmosaurus and Torosaurus than others. (see below).

>There is a distinct similarity between *Triceratops* and
*Torosaurus*, mostly the general appearance of the face, horns, nasal
fossa or whatever it's called, and frill, with Toro having small
fenestrae and a very smooth margin, kinda like some specimens of
Trike; in fact, the most similarity I can see is between the heads of
*Diceratops/Triceratops hatcheri* and *Torosaurus latus*. Andy Farke
may prove me wrong, as he seems to me the most ardent worker on Toro I
can find.

Nope, I won't prove you wrong, Jaime. Torosaurus and Triceratops both 
show trends towards closure of the postfrontal fossa, loss of parietal 
fenestrae and other things. There's quite a few other characters, 
published by Tom Lehman back in 1996, that back this up.

>They are basal Centrosaurinae, and Toro/Trike may be
advanced Chasmosaurinae. Some skulls of Trike are very similar to
centrosaurines, like *T. "obtusus"* and *T. "serratus"*, so they may
be basal, and the semi-solid (very thin on both trikes and Brachy and
Ada) mid parietals are quitre similar.

I only partly agree here. "T. obtusus" and "T. serratus" are probably 
not basal, but about as advanced as you could get. I agree that the 
parietals are similar, but they were acquired independently. My 
examination of the specimens shows that Avaceratops and Triceratops have 
few if any other similarities. The shape of the squamosal is 
characteristically centrosaurine in Avaceratops, and Triceratops has a 
chasmosaurine, although short, squamosal (I'll add here that there is 
some variation in that, too. I'm doing research on it at present).

>I have seen photographs of a recently-excavated specimen of 
_Torosaurus_ from ?Montana that has obvious epoccipitals, so despite the 
way this ceratopian has been reconstructed and restored over the years, 
it's apparent that it did indeed have them along the edge of the frill. 

It's been known since the 1940's that Torosaurus had epoccipitals. 
Gilmore, in his paper on Arrhinoceratops? (now Torosaurus) utahensis 
described about a dozen or so epoccipitals that were found with 
Torosaurus specimens in Utah. The specimen you mention from Montana is 
on display at the Milwaukee Public Museum, I believe. That specimen, as 
I will argue in my upcoming DinoFest paper, also represents T. 
utahensis. So, right now the best evidence is that T. utahensis had 
epoccipitals and T. latus didn't. BUT (and there is always an exception 
to every rule). . .

I had a chance to examine the T. latus female specimen on display at the 
Academy of Natural Sciences in Philadelphia. That animal was advanced in 
age when it died, so most everything was fused together. Along the edge 
of the squamosal, there are what appears to be 3 fused-on epoccipitals. 
(I took pictures) They seem to be long and low, and may not have 
disrupted the smooth border of the frill very much. However, due to the 
heavy amount of varnish and junk that's been applied over the years, 
it's difficult to tell if these are actual epoccipitals or if the bone 
is just worn here. I was able to see them only after crawling up on the 
mount and looking closely. Does anyone else have an opinion? 

>As for _Triceratops_, I would guess that most (if not all) of the 
specimens with "smooth-margined frills" are casts of the mount at the 
AMNH; the frill on that skull is *very* heavily reconstructed, and 
considering the evidence from other _Triceratops_ skulls, is undoubtedly 
wrong.

You're right here, Brian. Some of these smooth-margined Triceratops may 
be the result of the epoccipitals falling off. They tend to do that 
except in the oldest individuals. One juvenile Triceratops squamosal 
that I've seen had epoccipitals with it, but they had fallen off after 
death. The frill margin is very smooth otherwise, so that if the 
epoccipitals weren't associated with you never would have guessed that 
the little guy had them.

I'd be glad to here of anyone else's thoughts or comments on this!

Thanks,
Andy Farke

The Torosaurus Home Page
http://www.geocities.com/CapeCanaveral/Hangar/3404
andyfarke@hotmail.com


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