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

[John Scanlon <riversleigh@outbackatisa.com.au>]

For all those curious about gastroliths and too impatient to wait for the
papers to trickle out, Oliver Wings' 2004 dissertation is freely available
as a pdf from the Uni of Bonn:

http://hss.ulb.uni-bonn.de/diss_online/math_nat_fak/2004/wings_oliver/index.
htm

Take-home message: no evidence for a gizzard in non-avians, and incidental
ingestion may explain all other cases of gastroliths (including in
crocodilians).  There's a drawing on Wing's title page of a macronarian
eating a cycad that has rocks and clods still attached to its roots. Nice
summary of his conclusion.

We recover lots of nicely polished chert pebbles from Riversleigh
(Oligo-Miocene freshwater carbonate) fossil sites that also contain
dromornithid and casuariid bones, sometimes in discrete concentrations of up
to a few kilograms in direct association with drom skeletons (in low-energy
deposits, so that water transport and other concentrating mechanisms are
unlikely), so I'm sceptical about the generality of Wings' experimental
finding of 'no polish' in bird gastroliths.  He doesn't seem all that
positive about this either, but goes with the experimental evidence which is
fair enough.

Happy New Year,

John
 
-----------------------------------------------
Dr John D. Scanlon
Palaeontologist, 
Riversleigh Fossil Centre, Outback at Isa
19 Marian Street / PO Box 1094
Mount Isa  QLD  4825
AUSTRALIA
Ph:   07 4749 1555
Fax: 07 4743 6296
Email: riversleigh@outbackatisa.com.au
http://tinyurl.com/f2rby


> -----Original Message-----
> From: don ohmes [mailto:d_ohmes@yahoo.com]
> Sent: Sunday, December 31, 2006 12:27 AM
> To: dinosaur@usc.edu
> Subject: Re: Gastric stones of dinosaurs were not for milling food !
> 
> Curiosity is festering, and I don't seem to have (easy) access to these
> papers (any pdf's appreciated), so I'll just have to ask; does anybody
> know what the ostriches used in the Wings' study were eating?
> 
> Don
> 
> ----- Original Message ----
> From: Denver Fowler <df9465@yahoo.co.uk>
> To: dinosaur@usc.edu
> Sent: Saturday, December 30, 2006 6:45:10 AM
> Subject: Re: Gastric stones of dinosaurs were not for milling food !
> 
> 
> 
> >If the big rock exhibits the characteristic sheen
> 
> Wings' studies demonstrate unequivocally that genuine gastroliths from
> gastric mills of extant taxa do not have a 'characteristic sheen'. This is
> another 'urban myth' of palaeontology.
> 
> >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_?
> 
> Wings is in the process of publishing various papers from his thesis which
> answer this and other questions, and debunk old ideas. I suppose, look out
> for more on the horizon.
> 
> Regarding seismo... I don't have a strong opinion on the subject, but
> there are undoubtedly many pebble-cobble sized stones in various layers
> within the sandstones from which the skeleton was extracted. Having
> visited the site, I am more inclined to agree with Spencer Lucas (2000)
> that these are 'gastromyths' in Seismosaurus, although I believe Oliver
> Wings is inclined to think at least some of the stones may be genuine
> (those found within the body cavity itself). The choking idea is silly
> though: the 4 cervical vertebrae were isolated and eroded (Gillette 1992),
> not articulated and pristine, so the fact that they found a large stone
> where the throat 'could have been', means nothing.
> 
> I could ramble on, but I'm just re-iterating Oliver's work. I would
> suggest reading some of his papers, since they cover all this in
> exhaustive detail, or the soon-to-be-published-hopefully ones will.
> 
> D.
> 
> ref: NMMNH-2000-17-Lucas-gastromyths seismosaurus, gastroliths, sauropod,
> LJ, MOR Fm, Nm, USA
> 
> 
> 
> 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
> 
> 
> 
> 
> 
> 
> 
> 
> Send instant messages to your online friends http://uk.messenger.yahoo.com
> 
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