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THEROPOD GASTROLITHS



I used to think that, in dinosaurs, there might be a tidy correlation 
between herbivory and the presence of gastroliths. The _Nature_ 
communication about ornithomimids intimates this. However, there are 
of course extant carnivores (crocs, otariids, predatory birds) that 
have gastroliths, plus ant/termite-eaters including _Proteles_. 

As some of these animals are amphibious (in otariids, gastroliths, as 
in plesiosaurs, might equate with their swimming style (Taylor 
1987)), toothless, or are eating chitinous prey that take too long to 
masticate, it makes it a bit of a stretch to compare them with 
non-avian dinosaurs. HOWEVER, gastroliths have been reported from 
predatory theropods including _Poekilopleuron_ (Eudes-Deslongchamps 
1838: though Bob Bakker reminded me that a teleosaurid croc was found 
nearby this specimen), _Lourinhanosaurus_, _Baryonyx_ and a 
tyrannosaurid. David Varrichio discussed the latter at SVP '99: I 
think that previous reports have been deemed too dubious to be 
accepted.

Seeing as it's very unlikely that these megalosauroids, spinosauroids
allosauroids and tyrannosaurids were herbivorous, predatory 
dinosaurs probably did have gastroliths too. I suppose in some cases 
it might be possible that the animals ingested the stones 
accidentally though. Gastroliths in _Caudipteryx_ were recently used 
as evidence for it possibly being an ant-eater (Garner et al. 1999). 
I don't agree with this.

"I love cats... They taste just like chicken"

DARREN NAISH 
PALAEOBIOLOGY RESEARCH GROUP
School of Earth, Environmental & Physical Sciences
UNIVERSITY OF PORTSMOUTH
Burnaby Building
Burnaby Road                           email: darren.naish@port.ac.uk
Portsmouth UK                          tel: 01703 446718
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http://www.naish-zoology.com]