Re: Theropod eating and attacking

["Gigi Babcock or Ralph Miller III" <gbabcock@best.com>]

> Birds of prey and owls will regurgitate undigestible parts of their 
>prey
> in pellets.  Some are capable of digesting small bones.  Fish-eating
> birds usually have strong stomach acids and gizzards and digest fish
> bones, but a few also regurgitate pellets.  Theropods may have done
> either.  I wonder how one could tell from fossils which method they 
>were
> using?

It may (or may not) be informative to examine the fossils of theropods
which include the skeletal remains of swallowed prey.  I am listing those
which immediately come to mind, but would like to hear of any I may have
left out.  

The Solnhofen specimen of _Compsognathus_ had the articulated remains of
_Bavarisaurus_, a lizard, within its rib cage.  While not a complete
specimen (as some seem to believe), the _Bavarisaurus_ is complete from the
mid-thorax on back, and a jaw fragment near the _Compsognathus_ may also
belong to the lizard.  John Ostrum has suggested that this huge last meal
may have given the theropod a terminal case of indigestion!

Fossilized skeletons of _Coelophysis_ have been found with the jumbled
bones of _Coelophysis_ chicks inside.  This has been interpreted as
cannibalism.   (Don't try this at home).

Two crushed _Velociraptor_ chick skulls were found within a few feet of an
adult _Oviraptor_ and its nest.  It has been suggested that the parent
_Oviraptor_ may have lopped off the one-inch-long _Velociraptor_ heads to
facilitate feeding the postcranial _Velociraptor_ morsels to its young. 
This interpretation is based on similar behavior seen in _avian_ raptors. 
The _Velociraptor_ skulls obviously don't qualify as "swallowed prey" but
they may imply theropod eating behavior.

Half-digested fish scales from a three-foot-long fish were found inside the
ribs of the 30-foot-long _Baryonyx_.

_Science News_ reported that one of the specimens of _Sinosauropteryx_
included the jawbone of a tiny mammal in its gut, the first direct evidence
of dinosaurs preying on mammals.  

For the most part, these fossils give us evidence of relatively small
dinosaurs swallowing smaller prey.  I don't know what these finds indicate
about whether theropods "horked up" pellets or not.  I leave it to others
to speculate.

On a lighter note, I have read that roadrunners have been observed grabbing
lizards by the tail and bashing the hapless creatures on rocks "for nearly
half an hour."  Although the lizards die quickly, the beating goes on and
on to crush the bones of the prey for easier swallowing.  While this
strategy could have conceivably been employed by theropods in danger of
biting off more than they could chew, the relatively pristine condition of
the _Bavarisaurus_ remains argues against this.

Bon appetit!

Ralph Miller III <gbabcock@best.com>