Re: oviraptor diet

["Jaime A. Headden" <qilongia@yahoo.com>]

Nick Longrich (longrich@alumni.princeton.edu) wrote:

<Well, you gotta admit though that the egg/skeleton association was the
major piece of evidence provided for egg-eating and the brooding
oviraptorids found by Norell, Currie, etc. pretty well killed that
argument.>

  Only for those that thought that the nest was evidence of this idea. And
yes, this was perpetuated in nearly every publication since. However,
Osborn drew two features out fo the skull that led to the name _along
with_ the nest, including the medioventral maxillary prongs and the
edentulous jaws that led to to the name. The nest was not the only
criterion, but this appears to have been what Ken chose to refute the name
by. That was the main point of my rant.

<As for what they were eating-  It seems to me that real durophagy -
crunching hard thingies, incl. eggs, bones, molluscs- is not supported by
the evidence. We'd expect to see convergences on durophagous vertebrates,
which include stuff like sea otters, porcupine fish, wolf eels, rays,
hyenas, walri, etc. .>

  Some sharks, too... and one especially adapted snake. Yes, a broad,
extensive, and adapted palate is useful.... Aardwolves (*Proteles*) and
hyaenids have extensive palates that are very useful for this. The
postcanines in the former are so reduced, but they lack any crushing diet.
However, hyaenids are the only primarily adapted mammals for durophagous
diets, and they do have robust teeth. The problem is, aside from a few
crocs, the mosasaur (below), and hyaenids, all other durophagous animals
have no teeth. I attempt to describe the jaw function in relation to
oviraptors in my manuscript, but it appears that the palate was adapted to
assist the teeth, rather than anything else, and yes, they are also
durophagous in appearance. This may be a means to handle large bones in
their intake, compensatory to their feeding style. The jaws have a
twist-and-pull design that would require such specialized teeth, so there
may be other reasons this occurs. I was also of the impression that
juvenile tyrannosaurs had blade-like rather than "banana-shaped" (c) Holtz
teeth. This is the case in *Tyrannosaurus* (= Nanotyrannus) and
*Albertosaurus*.

<These guys tend to have massive, platelike or bulbous crushing surfaces,
usually teeth, which are usually in the rear of the jaws (my favorite
though has got to be those ball-bearing shaped teeth in that one
mosasaur).>

  Globidontine mosasaurs?

<Using this line of argument, durophagy is probably better supported for
juvenile tyrannosaurs (no s***, these are remarkably robust for their
length) than for oviraptorosaurs. Oviraptorosaurs have rather bladelike
cutting surfaces on the edges of the dentaries, so they don't really seem
to fit the pattern seen among hard-core durophages; you'd probably expect
to instead see relatively few short, massive teeth or many teeth arrayed
into crushing plates.>

  I hope to show that a novel feeding style was adapted. We keep seeing
this as take a bone and jog around with it like some happy dog, the ends
jutting out of each side of the mouth. But the jaws of oviraptorids are
very different and I hope to present an alternative view. 

<The most obviously similar fossil animals seem to be the dicynodonts, as
Cracraft argued. This would seem to answer the problem of oviraptorids
-they're convergent on dicynodonts-, except for there's that minor little
detail; OK, well, what the heck were dicynodonts doing? Finally, flipping
through the revision of Analysis of Vertebrate Structure (Hildebrand and
Goslow) I stopped on page 273 and my jaw just about dropped when I
realized that the "dicynodont" skull I though I was looking at was
actually a Galapagos turtle. Aldabra tortoises are pretty similar too.>

  
<Anyways, it sounds like these guys are capable of chopping some pretty
tough, fibrous vegetation- grasses, sedges, cactus, and woody plants,
although they also will eat carrion, inverts, etc. My guess then is that
oviraptorids were primarily herbivores, but if so probably were able to
cope with far tougher, more fibrous material than were the ornithomimids,
which were probably also herbivores/omnivores (supposed evidence of filter
feeding notwithstanding). Besides the powerful forces involved in closing
the jaws, there was probably a substantial translational movement of the
jaws- that is, as the beak came together, the beak edges slid relative to
each other, this would be particularly effective in generating a slicing
motion to shred plants.>

  About the only thing that oviraptorid jaws and dicynodonts share is the
bicondylar jaw joint, allowing translation of the jaws, and the
longitudinal ridges on the palate. Problem is, so far only Hotton has
presented a fair treatment of what they may have done to eat, in his paper
on *Kuwiangosaurus*, and that was to conclude they were particularly weak
biters, and may have sawed plant matter.

  I would say more, explain why I feel there's more wrong with the theory,
and would have in the poster I didn't get to present, but I'd rather leave
this for the paper. Not really trying to be secretive....

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

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