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Re: Gastric stones of dinosaurs were not for milling food !
Thanks! "Free range ostriches" is as far as Wings takes it in the '03 paper...
makes me wonder what gastroliths of ostriches would look like in a more
controlled situation (birds restricted to a leafy diet w/ stones of uniform
size/composition and no sand in the mix). Unfortunately, ostrich farms are a
thing of the past around here. That said, I find the evidence against sauro
gastric mills convincing, especially the stone/body-mass ratios.
For those who don't mind questioning the steady-state N2 partial pressure
assumption: as any farm boy knows, the application of nitrogen fertilizer to
pastures increases both mass-specific biomass nutritional values and per acre
biomass production per unit time. It seems logical on a 'mechanical' basis that
a lightning stroke would produce free nitrogen in proportion to N2 partial
pressure, w/ obvious implications for herbivores, although the response of
nitrogen-fixing bacteria to an increase in ambient N2 pressure is unclear, at
least to me. I have been unable to find any studies of N2 fixation rates,
either bacterial or abiotic, relative to altitude. Although it has been 5 years
since I last looked. That said, an inverse relationship seems unlikely,
excluding temperature effects.
In any case, combined with the implications of lowered evaporation rates (less
water loss relative to leaf area), postulating increased N2 partial
paleo-pressure would seem to allow estimates of mass-specific browse
nutritional values, total biomass production and browse digestibility to be
raised, possibly significantly. How much is entirely an open question, of
course, but there are obvious attractions for those who wonder how in the heck
those huge critters gathered enough leaf-mass in the course of 24 hours to
support themselves.
A lot less speculative than connecting head/heart height differential to
atmospheric pressure, but still fun, IMO.
Happy New Year,
Don
----- Original Message ----
From: Denver Fowler <df9465@yahoo.co.uk>
To: dinosaur@usc.edu
Sent: Saturday, December 30, 2006 9:33:53 AM
Subject: Re: Gastric stones of dinosaurs were not for milling food !
various pdfs of Oliver Wings' work, plus his unpublished PhD thesis are
available or linked on the downloads part of his webpage:
http://www.dinosaurhunter.org/index.php?article_id=9
phd title (in process of being published, some in review etc):
Identification, Distribution, and Function of
Gastroliths in Dinosaurs and Extant Birds with Emphasis on Ostriches
(Struthio
camelus)
cheers,
Denver.
----------------------------------
Fieldwork pictures NM 2002-4 & China 06:
http://www.statemuseumpa.org/notes05.htm
http://www.wald.heim.at/urwald/540645/JH-Projekte/China_04-2006/chinaset.htm
Art:
http://dino.lm.com/artists/display.php?name=df9465
Work:
http://www.impossiblepictures.co.uk
-----------------------------------
----- Original Message ----
From: don ohmes <d_ohmes@yahoo.com>
To: dinosaur@usc.edu
Sent: Saturday, 30 December, 2006 2:26:31 PM
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
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
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