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Larry asked..

> Is there stomach-content evidence that the machine 
> gun-toting gorillas of the deep preyed upon other large 
> marine reptiles?  I've read of ammonites found, but not large 
> vertebrate contents.   Just curious.

You ask specifically about stomach contents - this narrows the body of evidence
considerably as there is very little data. A famous _Liopleurodon_ specimen from
Peterborough, described by Martill in _Mercian Geologist_ (round 1987 I think),
has a stomach full of old junk. Numerous belemnite hooks, fish scales and sand
and stones (all plesiosaurs swallowed stones). Dave Martill did recently suggest
that pliosaurids were therefore like Tiger sharks (_Galeocerdo cuvier_*) and
swam round swallowing everything within reach (UNLIKE _Carcharodon_, a selective
predator - see previous posts). Mmmmmm, maybe, but this _Liopleurodon_ was a
juvenile or subadult and I _suspect_ that it was not doing the same thing as
adults of its genus. I don't think a 12 m adult _Liopleurodon_ would waste time
on belemnites when it lived in a sea full of ichthyosaurs and other plesiosaurs.
However, here we leave the stomach content data and go into speculation.

Among the pliosaurids that are not _Liopleurodon_, _Kronosaurus queenslandicus_
has yielded pieces of turtle shell, bits of fish and parts of the elasmosaurid
_Woolungasaurus_. This is probably more reflective of adult pliosaur diet. Judy
Massare's 1987 paper (_JVP_) has a table of stomach contents - I forget if there
is any pliosaur data in there but I suspect so.

OK.. so that's your stomach content data. What about other evidence for pliosaur
diet? Well, there __are__ many pliosaur-bitten bones from Mesozoic marine
deposits. Numerous such chewed bones, including those of cryptoclidids and the
marine croc _Metriorhynchus_, are known from the Oxford Clay. They reveal tooth
marks that match the tooth size and spacing of large pliosaurids like
_Pliosaurus_ and _Liopleurodon_. Best of all though is an elasmosaurid skull
first described by Persson in _Mem. Queensland Mus._. Ooops - he confused holes
in the palate with eye sockets and did not note the enormous pliosaur tooth
marks that occur on both dorsal and ventral surfaces of the skull. Tony Thulborn
and ?Angela Turner (_Modern Geology_) did however, and presented this skull as
exciting evidence for pliosaur diet. The damage was probably done by a kronosaur
- the elasmosaurid skull had been pancaked in the pliosaur's jaws and separated
from the rest of the body. Perhaps, as Persson did actually suggest, pliosaurs
bit the heads off long-necked plesiosaurs and then ate the immobilised body.
Finally... what are all those dinosaur bones doing in marine sediments? I'll
leave that for you to speculate about yourself.

So, what does a big pliosaur eat? A: Whatever it wants!

I have to go as this machine is about to crash.

*The specific name is no longer _cuveiri_.