Re: POISONOUS BIRDS, GASTROLITHS

["Steve Brusatte" <dinoland@lycos.com>]

On Tue, 27 Aug 2002 10:25:21  
 darren.naish wrote:
 Use of gastroliths for buoyancy control (Mike 
>Taylor's contention) is being contested by Mike Everhart 
>who has evidence suggesting that plesiosaur gastroliths 
>were being used to mash up fish.. however, the two 
>functions are not necessarily exclusive. 

I knew I heard this somewhere!  Actually, this seems very similar to the 
various hypotheses of gastrolith use in otariids.  One study seemed to indicate 
that they were used in locomotion, and another that they were used to grind 
fish bones.  But, no, the two certainly are not mutually exclusive.  It's 
interesting to see yet another example of convergence.

Use of gastroliths in 
>otariids is argued to augment their 'flying' style of 
>locomotion and is apparently not for deep diving (IIRC the 
>deepest diving pinnipeds are elephant seals, not otariids). 

Interesting.  I thought I read somewhere that otariids were the deepest 
pinniped divers, but I must be wrong about that.  Regardless, if otariid 
gastroliths are used to augment "underwater flight," then otariid gastroliths 
might be a perfect correlation to plesiosaur gastroliths.  Both distantly 
related groups might have used gastroliths for both feeding (on fish) and to 
help with underwater flight.

Thanks to HP Naish for another informative post!

Steve

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