Re: oviraptor diet

[Nick Longrich <longrich@alumni.princeton.edu>]

> The problem is, aside from a few
> crocs, the mosasaur (below), and hyaenids, all other durophagous animals
> have no teeth.
	Both sea otters and walruses have massive crushing teeth to 
deal with molluscs, not to mention placodonts although their 
durophagy is inferred, rather than known, from their 
otter/walrus-like dentition. Porcupine fish and wolf eels have a few 
massive teeth, while rays have crushing plates formed by batteries of 
interlocking hexagonal teeth. King crab of course lack teeth, but 
massive, bulbous, molar-like structures exist in the back of their 
crusher claws, which function like crushing teeth to allow them to 
break open shellfish.
	At least in hyenas, king crab, and sea otters, the hinges 
bringing the crushing surfaces together are strong but very simple. 
Oviraptorids and caenagnathids are clearly doing something different 
with those anteroposteriorly elongate hinges, which were not just 
generating a simple open-close movement.
	Oviraptorids do have those weird palatal projections; however 
the problem with these is that the crushing surfaces in durophages- 
otters, king crab, rays, whatever- are basically hammer-on-anvil 
affairs; oviraptorid palatal projections don't really oppose anything 
except maybe the tongue, and the dentary has surfaces that are thin 
and sharp edges- cutting surfaces, not crushing surfaces.
	Egg-eating snakes don't really seem to provide a good 
comparison either; the jaws are able to separate at the symphysis 
allowing them to get really large eggs into the mouth and then the 
gullet where they're crushed; oviraptorid jaws were fused at the 
symphysis, and so essentially inflexible.
	One could propose a novel system for oviraptorids, but in 
general, it's easier to go with a known. If you're got an extant 
animal doing something similar, you know with 100% certainty that the 
system will work simply because it has evolved. Without that, it's 
difficult to be certain of the feasibility from a mechanical, 
ecological, or evolutionary standpoint. For this reason, I think the 
Novel Function card should be held back until you have nothing else 
to play. Novel functions clearly must have existed and many aspects 
of mesozoic biology lack parallels, but generally speaking it seems 
that if it was a good, feasible idea once, it will tend to evolve 
many times and tend to be seen in extant animals.

>   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 think that there are a few more similarities that may be 
significant- lack of (all but two) teeth, the greatly shortened 
preorbital region, the way the skull looks sort of bent at its 
midpoint, the extremely short dentaries expanded at midlength, the 
large area for supratemporal musculature, the way the palate seems to 
project ventrally; much of this also holds for the large herbivorous 
tortoises as well. I find it difficult to buy dicynodonts as weak 
biters- the large muscle attachment surfaces and the extremely short, 
deep jaws seem to suggest that they were resisting very large forces. 
Personally, I imagine that a large one could easily bite a couple of 
fingers off. It just seems like slicing up and cropping tough plants 
would be the easiest answer, also the denticulate edge of the 
premaxilla resembles duckbill dinosaurs.
	As for whether in this scenario they could have attacked 
other things besides plants- again, modern tortoises certainly do. 
One would imagine that oviraptorosaurs would vary much like any group 
of animals- some might verge on strict veganism, others might take a 
substantial part of the diet in the form of insects and 
invertebrates. I could maybe see those jaws as being effective in 
cracking seeds. The claws are remarkably nasty-looking in O. 
philoceratops, although some others were clearly doing different 
things and have straighter claws, and there's Ingenia, whatever the 
big manual ungual was doing- digging for roots or whatever. Also, 
it's worth considering whether an animal like the big mother 
oviraptorid could possibly have caught enough little tiny lizards to 
supply its calorie needs. That, and the differences in morphology of 
the oviraptorid jaws is pretty striking- Dinosaur Provincial Park 
alone seems to have three distinct jaw designs, presumably they were 
not all up to exactly the same thing.


Nick Longrich


"..love, love, love/ well, that's like hypnotizing chickens." -Iggy Pop