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Ceratopsian frill size (was Re: DINOSAUR digest 71)



At 01:54 PM 9/24/96 -0500, martin writes:

>I asked a long time ago whether frill size could be correlated to
>major predator jaw gape, and the reply was along the lines of
>"unlikely, as other small-frilled ceratopsians were
>co-existant". However, I don't think the reply took into account:
> 
>1) different predators for different prey species
>2) different environments   "" "" "" 
>3) different behaviour    "" "" "", particularly when faced with predators

This would not affect things that much.  An animal like _T. rex_
wouldn't hesitate to lunch on _Leptoceratops_ if the latter was
available to the former (the size of the prey doesn't matter all that
much to the predators).  IMHO, frill size is more likely an indication
of the chewing power of the animal, rather than the jaw gape of the
primary predator.

>The other point I want to make about frill size/heat radiation is: why would 
>ceratopsians have different sized frills (assuming they did live concurrently) 
>if:
>
>1) they inhabit similar environments (did they?)
>2) are similar-sized 
>3) have similar basic metabolisms?

These points are better explained by the idea that they were feeding
on different types of vegetation.  The ceratopian skull is perfectly
designed to allow many ceratopian species to exist within the same
area.  Start with the beak itself; it allows the animal to be
selective of the food it consumes.  Add to this the varying frill
heights, allowing different genera to consume food sources with
different plant toughness (an animal like _Chasmosaurus_ can consume
vegetation that is considerably tougher than an animal like
_Eucentrosaurus_).

The frill-radiator hypothesis has one fatal flaw: the ceratopian frill
doesn't allow the airflow necessary for proper cooling (especially for
the short-frilled genera).

Rob Meyerson
Orphan Vertebrate Paleontologist

***
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