Re: Dinosaur Diets

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

In response to the dino-diet thread on the list, I have this to say:

First of all, we can't truly tell what any dino's diet might have 
consisted of, even when we have coprolites, because we don't know which 
dinosaurs laid those things. Sometimes, in a great long while, we'll 
find something that will help us, like the *Coelophyses* (plural) that 
had juveniles or hatchlings of their own kind into their stomach region, 
or the *Compsognathus* with the *Bavariasaurus* lizard in its stomach. 
We get an idea of the diet, but only a small part. No animal alive eats 
its own young (or the young of others) habitually, nor is it totally 
lacertivorous (lizard-eating -- but I don't think there's any such word, 
so I may have just invented it -- I don't know) and lastly we have those 
dinosaurs (sauropods and prosauropods, I think) who had gastroliths in 
their bellies.

Dentition could give us a clue, but only a partial one. Back-curved 
teeth would have torn flesh, strait-shafted teeth would have pierced 
then sawed, strait unserrated teeth would have been best suited for 
grasping, spoonlike teeth for shearing or holding, peg- or pencil- 
shaped teeth for picking and plucking (a tongue or mobile lips would 
have facilitated this) and leaf-shaped teeth for sawing; a form of the 
last, arranged in multiple rows and set on a sliding-hinged jaw, would 
have been used for grinding and _chewing_.

So we have pointers for diet by dentition, but not what would have 
composed of the food. For there are those theropods who lacked teeth at 
all (advanced ornithomimids, oviraptorosaurs -- though they had little 
tooth-like prongs on their palate bones that could have been used for 
cracking or puncturing, much like consitrictors and egg- eating snakes 
use their back teeth to squish soft eggs open -- avimimids, and of 
course, birds -- whom we have hands on evidence for the diet of).

I've seen countless articles on the possible scavengry of larger 
theropods, as opposed to hunter, and all I can say is that not one 
animal living today that hunts will not resort to scavenging when times 
are scarce or the pickings are easier than hunting down. Trackways of 
large theropods chasing (or stalking) herbivores is evidence of hunting 
behavior. Hyenas can chase down zebra as well as chase of a lioness or a 
group of them from a zebra the lions killed. Cape hunting dogs of 
Africa, personal favorites of mine, will more often than not hunt and 
chase than scavenge, and even vultures will kill. Animals today who are 
more suited to hunting will chance at taking food from another carnivore 
if they need to -- some will fail, but the Siberian tiger, largest land 
predator alive, will take food from another tiger to feed.

Other behavior as bone-cracking as performed by vultures by dropping 
stones to get at the marrow, or hyenas whose jaws are well-suited for 
smashing long bones to get at their rich source of protein, could also 
be used by dinosaurs, even herbivores, but I do not know any evidence of 
bones smashed apart in an obvious attempt to get at marrow, unless there 
are other bones we think were smashed during fossilization that could be 
this evidence. . . .

But as it is, basing evidence on mere dentition, though indicative, is 
not definative, and likely never will be. We would need to find a 
dinosaur actually chewing on a bone to prove that, or an egg in 
another's jaws to prove that. This brings me to a point: why was 
*Protoceratops* always hanging around nests of *Oviraptor*, those 
*Elongoolithus* eggs long confused for the herbivore's simply because of 
its presence? Maybe ceratopsians or protoceratopsians (even 
psittacorsaurs) were egg-eaters in slim times, for they seem to be in 
desert environments lacking in sufficient vegetation to support as many 
as there were, or we think there were, like the numerous *Protoceratops* 
in the fossil record. Proteins from eggs, laid in plenty as discovered 
by the expedition led by ROy Chapman Andrews to Mongolia way back. The 
Flaming Cliffs, back in the Mesozoic, would have been possibly rich in 
such habits. The famous *Protoceratops* and the *Velociraptor* death 
scene (struggle?) has the raptor's arm in the proto's beak -- fight, 
possibly, but who was whose prey?

Is the fauna and flora of such environments rich in fossils as the Hell 
Creek, Santana, Ischigualasto, Judith River and Horseshoe Bend, Nemegt, 
Dashanpu, Stormberg, Baharija, Shangshaximiao, and Stubensandstein well 
known enough to postulate such a rich environment? How about other 
formations? I know that the Chinle and Petrified Forest Formations have 
been well plotted for their inclusion of *Dilophosaurus* and the 
incredible Ghost Ranch Quarry and it's *Coelophyses* in abundance. Such 
information may lead to a better understanding of paleo- environments, 
and evenpossibly a small part of the paleo-ecology and biosystems we 
known to have been there.

Further evidence will help, as will full plotting of the world's 
ecoloies and geographies back in the Mesozoic, from the Carnian to the 
Maastrichtian.

Jaime A. Headden.

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