Re: Theropod eating and attacking

[jdharris@post.cis.smu.edu (Jerry D. Harris)]

At 6:41 PM 8/20/97, bruce thompson wrote:
>>>   Would theropods swallow the bones?
>
>Is Coelophysis a theropod?  In _The Little Dinosaurs of Ghost Ranch_,
>cannibalism in those animals was deduced from bones found in one's body
>cavity.

        _Coelophysis_ is a theropod.  So is _Compsognathus_, which was
found with the skeleton of the lepidosaur _Bavariasaurus_ in its gut.  From
both of these, we can conclude that, when the prey animal was substantially
smaller than the theropod, at least some theropods did indeed swallow the
prey whole (hence Greg Paul's wonderful picture of _Compsognathus_ with the
lizard tail hanging out of its mouth -- as for William Stout's _Alioramus_
swallowing a larger, indeterminate animal...well, I'm not so sure about
that one).  However, I seriously doubt that even the big-headed
tyrannosaurids would have picked up and tried to swallow something as long
and unwieldly as a hadrosaur or ceratopsian humerus or rib, or something as
massive as one of their vertebrae.  Besides, the larger animals probably
had larger, thicker chunks of meat on their bones (insert Son Seals music
here), more suitable for tearing off and gulping down.  However, if a
tyrannosaurid caught a much smaller animal -- say, a large didelphid mammal
or a big varanoid lizard, then I'd bet it would probably swallow it whole.
Not to bring up a sore (saur?) point here, but this really bugged me about
the large tyrannosaurs in _JP_ and _TLW_ having to tear apart the
relatively meat-less humans...

        The question is more one of:  if (when) theropods swallowed bones,
how quickly did the food pass through their digestive tracts?  Karen Chin's
bone bits in theropod coprolites suggests that the material stayed in an
intestinal acid bath long enough to dissolve most of the bone matter.  This
is also supported by numerous (accidentally) ingested theropod teeth, which
show substantial dissolution.  This is unlike the strategy seen in owls and
other "raptorial" avians, in which things pass through the tract so quickly
that the bones are not greatly dissolved, and they must be hocked back up
in pellets.  In this particular sense, I would guess that theropods were a
little less avian than "typically" reptilian (if such a thing exists...)

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Jerry D. Harris                       (214) 768-2750
Dept. of Geological Sciences          FAX:  768-2701
Southern Methodist University
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