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oviraptor diet

  I'm glad people now look at the fossils instead of their associations to
prove the inappropriateness of names. No, this is not intended to focus on
what Ken said, but it reflects a greater problem I have written on before
and will be publishing on soon. I wrote an unpresented abstract for the
2001 meeting of the SVP (financial problems forbade my getting to Bozeman)
that I am presently working the full piece out. Essentially, the abstract
points at the apparent idea that because an oviraptorid was found atop a
nest, it meant that "no, it did not eat eggs." This is dumb science, sorry
if this offends anyone. Analysis of the jaws presented by Barsbold in 1977
(paper available from me or Tracy if anyone wants it, it's in Russian,
though) and mechanics examined (but not elaborated upon) by Smith in 1992
(Neues Jaerhbuch, Abh.) show that the jaw was fully capable of a range of
mechanical crushing-related properties. Instead of looking at the jaws,
the pop-sci boys looked at the nest and made their minds up about it's
dietary habits. One looks at _jaws_ to find out how an animal eats (well,
okay, in myrmecophages, you look at the sternum, too :) ).

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. 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. . 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). 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.
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.