RE: Gastric stones of dinosaurs were not for milling food !

[Dino Guy Ralph <dinoguy@sbcglobal.net>]

Glen Ledingham wrote:   

>I recall an article's stating that a sauropod had
apparently choked to death on a gastrolith it was
swallowing.  This would indicate that that particular
ingestion was deliberate, not incidental.
 ---

David Gillette said that the _Seismosaurus_ holotype (now thought to be
_Diplodocus_) must have choked to death on the largest stone found among the
associated gastroliths.  If my memory serves me, the other gastroliths were
plum-sized, and the largest stone was quite a bit larger
(grapefruit-sized?).  I puzzle at an animal foolish enough to choke on an
outsize rock surviving to such a ripe old age.  Would a rock of that size
choke such a big sauropod?  

And did the big rock have the waxy surface sheen as the other purported
gastroliths?  If the sheen resulted from an extended stay in the gizzard,
then the big rock must have likewise resided in the gizzard for some time,
falsifying the death by choking hypothesis.  

If the big rock exhibits the characteristic sheen yet was indeed swallowed
shortly before the animal choked to death, then said rock must have either
had the sheen prior to ingestion or it must have developed its waxy texture
post mortem, and so the waxy sheen may not have resulted from gizzard
processing.  This scenario calls into question the surface texture as an
indicator of gizzard residence.

So... what are the surface characteristics of bona fide non-avian
gastroliths, those found within the complete torsos of dinosaur specimens
such as _Sinornithomimus_ or _Caudipteryx_?       

So many questions.

---Ralph

Dino Guy Ralph
Docent at the California Academy of Sciences
Dinosaur and Fossil Education
Member of the Society of Vertebrate Paleontology