Re: Omnivorous dinosaurs

[Dann Pigdon <dannj@alphalink.com.au>]

Karen Casino writes: 

> Are there any anatomical features that indicate omnivory (sic - what  
> would this word be?), and if so, do any dinosaurs have them? Is there  a 
> distinction between omnivores that can eat a variety of foods and  those 
> that have to eat a variety of foods? What distinctions are made  between 
> opportunistic feeding (the grass-eating dogs and chicken- eating mules of 
> the world) and genuinely omnivorous behavior?

Firstly; there is almost no such thing as a pure carnivore or herbivore. 
Most carnivores get some sort of plant matter in their diet, if only in the 
form of another animal's gut contents. Herbivores also get a reasonable 
amount of protein swallowing insects and the like that cling to vegetation 
(in fact, a lot of parasitic organisms rely on it). The lines between 
carnivore, onmivore and herbivore can get fairly blurry. 

It can be extremely difficult to tell with any degree of certainty from 
fossil remains exactly what range of foods any particular species ate. 
Coprolites may be an exception - although identifying which species made 
them isn't easy. I'm fairly sure that no-one has ever found dinosaur 
coprolites with both bone bone fragments and plant matter in them though. 

Ornithomimosaurs have been suggested to be omnivores mostly because they 
were theropods (a primarily carnivorous grouping at the time) with no 
specific carnivorous adaptations (such as sharp teeth or recurved claws). 
They could still have swallowed small animals whole though. If so, they may 
never have eaten much in the way of plant matter at all. 

Muttaburrasaurus and ceratopians in general have been suggested to be 
partially carnivorous, due to the shearing nature of their dentition and 
their powerful jaw muscles. Of course just because a creature was physically 
capable of doing something doesn't mean it was necessarily part of their 
behavioural repertoire. 

See also the 'dinosaur diet' thread from 1997: 

http://dml.cmnh.org/1997Dec/msg00272.html 

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Dann Pigdon
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://heretichides.soffiles.com
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