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

[Dann Pigdon <dannj@alphalink.com.au>]

Richard W. Travsky writes: 

> On Thu, 21 Dec 2006, Dora Smith wrote:
> > I missed just one detail. 
> >
> > If the stones were not for milling food, what were they for?
>
> One article suggested it was for the mineral content, my thought is
> ingestion was incidental ;)

There's one easy way to tell dietry from non-dietry ingestion of stones; if 
the stones were vitrious (like quartz) then they almost certainly weren't 
ingested for mineral content. If, on the other hand, the stones contained 
significant amounts of carbonate (or any other disolvable minerals) then 
there's a chance they were like internal salt licks. Of course, carbonate 
minerals probably wouldn't last long enough to end up in the fossil record, 
unless death was soon after ingestion. 

Personally, I'd have thought that loose sediment would have been a better 
source of minerals than stones (lots of modern species eat clay for example, 
even humans). Perhaps the stones were collected unintentionally along with 
sediments? If so, then they were unintentionally swallowed during the act of 
intentionally aquiring minerals (therefore sort of semi-intentional). That 
said, some of those stones would have been more than noticable on the way 
down. It's hard to imagine a sauropod swallowing a fist-sized stone by 
accident - unless they provided both mineral content AND a mechanical 
digestive advantage. Crocs certainly use gastroliths for more than one 
purpose. 

___________________________________________________________________ 

Dann Pigdon
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://heretichides.soffiles.com
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