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Re: Velociraptor scavenged azhdarchid pterosaur



On Mar 4, 2012, at 7:39 PM, Dann Pigdon wrote:

> On Sun, March 4, 2012 6:47 pm, Habib, Michael wrote:
>> Parrots and giant tortoises immediately come to mind.
> 
> Indeed - and Keas in New Zealand are known to be predatory. There are 
> numerous reports of 
> them attacking sheep, seeming to prefer tearing out the fat around their 
> flanks. Sometimes the 
> sheep survive, even if the wounds open up the intestinal tract, and they end 
> up defecating out of 
> the newly healed opening in the flank. Yuck.

Yuck indeed.  Yes, Keas are omnivorous.  They also have *less* reinforced jaws 
than many other parrots.  The heaviest jaws among parrots belong to nut-eating 
specialists.  The point is that powerful jaws are often adaptations to 
herbivory.  In fact, I'll bet that if you looked at *average* jaw forces across 
trophic categories, herbivores would actually have stronger jaws than predators.


> Neither parrots nor giant tortoises have the rediculous degree of 
> over-engineering you see in 
> ceratopsian jaws though.

Are you sure?  Any numbers on that?  Because when a 1 kg parrot can crack a 
brazil nut in a single bite, I'm willing to wager that some remarkable 
comparative reaction forces are involved.


> I quite like Mark Witton's take on the issue:
> http://horneddinosaurs.blogspot.com.au/2011/02/were-ceratopsians-strict-herbivores.html

Yes, I am a fan as well.  Incidentally, I am not suggesting that ceratopsians 
could not be omnivores, but rather that powerful bite forces don't really 
suggest predatory habits.  Strong bites are plenty common among herbivores.

Oh, and keep in mind that there are some very nice recent data on ceratopsian 
feeding mechanics: Frank Varriale has put together a really knock-out microwear 
study on marginocephalians.  In fact, he presented on it at SVP in Vegas, and 
won the Romer Prize for the work.  So if we want to test hypotheses of 
omnivory, going to something like his microwear work would seem to be the best 
option; rather better than speculating from potential bite forces, I suggest.


> What Mesozoic plants present in the environment of protoceratops could have 
> possibly warranted 
> such an extreme jaw configuration? The Mesozoic equivalents of coconuts 
> perhaps?

Anything woody. Even dry environments have tough plants.  Besides, what sort of 
predation would warrant that sort of jaw configuration?  Only a few forms of 
predation actually select for extreme jaw forces, the most obvious being 
durophagy.

Cheers,

--Mike Habib


Michael Habib
Assistant Professor of Biology
Chatham University
Woodland Road, Pittsburgh PA  15232
Buhl Hall, Room 226A
mhabib@chatham.edu
(443) 280-0181