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Stomach Stones?


DE&i

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I’ve just read that palaeontologists are researching new methods of identifying Gastroliths that have been found disassociated from animal remains. Could anyone further enhance this piece of information for me please, I have some suspect marine reptile stomach stones found in this same way. And would really like to put them to rest one way or another.


Darren.

Regards.....D&E&i

The only certainty with fossil hunting is the uncertainty.

https://lnk.bio/Darren.Withers

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I'm not sure what the pros have come up with, but here is my understanding of some of the past ID conventions. Obviously, the ideal is to find a pile of stones in the gut area of a complete skeleton. Of course, gastroliths were apparently periodically expelled as vomitus, so piles without a deceased donor exist. It is my understanding that ID takes into account - the presence of stones not present in the local area; a worn, smoothed appearance with a "silky" luster and unpolished low areas on the surface. The last trait recognizing the fact that the other major producer of smooth stones, water, is an equal opportunity polisher, reaching all areas of the stone. The animal's gut polishes via abrasion with other stones. This hits the high spots, but leaves depressions in the surface untouched. Here is a gastrolith that I think illustrates this. Check out the unpolished depressions at the lower middle and right. In hand this piece is much smoother and silky looking than the photo reveals. I hope someone else will report any new revelations in this area.

post-8873-0-33515500-1366247699_thumb.jpg

Human beings, who are almost unique in having the ability to learn from the experience of others, also are remarkable for their apparent disinclination to do so. - Douglas Adams, Last Chance to See

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Thank you so much for your reply very informative there’s a lot of tell-tale signs I can take from that. Here are four examples I have….feels a bit odd posting photos of stones and hoping for the kind of answer I’m looking for.


The photos are front and back of each one of the four stones, all I’ve done is wipe the lose clay off with a damp cloth.


Darren.

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Regards.....D&E&i

The only certainty with fossil hunting is the uncertainty.

https://lnk.bio/Darren.Withers

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These items are, as you say, associated with marine reptiles as well as dinosaurs – although they served different purposes. Generally, aquatic animals swallowed them as ballast to help control their buoyancy in water. In dinosaurs they were a digestive aid. And they’re not always ancient. Modern crocodiles, alligators and seals still swallow stones, as do some birds with a mainly herbivorous diet – notably ostriches – also for digestive reasons.


In the most studied palaeontological case (a Cedarosaurus dinosaur found in Utah) the gastrolith set comprised 115 stones with a total weight of 15 lbs. More than half of the stones were less than half an inch across, but the largest weighed 25 ounces. There’s no firm evidence to suggest that dinosaurs were selective about the nature of the stones with respect to type, size or shape. The Utah Cedarosaurus set included chert (some with fossils!), sandstone, siltstone and quartzite in a variety of colours. Occasionally, petrified wood examples have been found.


The pointers generally are:

- Unlike other rocks found in the vicinity.

- Typically found in clusters occupying a very small area.

- Found in association with appropriate fossils.

- Rounded and polished, even if they started life as being angular (note that stones from birds and aquatic buoyancy stones may not show any evidence of polishing at all).

- Highly polished on higher surfaces with little or no polish in depressions or crevices (similar to the surfaces of worn teeth) which
is not the case for water-polished rocks.

- Sometimes, long microscopic hairline scratches on highly polished surfaces (caused by the sharp edge of a freshly swallowed stone acting on one that’s been in situ for a while).

- High surface reflectance value (greater than 50%, versus water-polished rocks typically at less than 35%)… ie they are very shiny.

- Colour tends to be dull, not bright or garish.

- Size depends on the animal concerned and varies wildly, but a little smaller than your fist would be typical for your average large sauropod.

As snolly50 says, there is normally an obvious difference between the polishing of the main surfaces and depressions in the surface. Here’s a couple of pics that show the difference in polish between the two areas:

post-6208-0-50975700-1366311569_thumb.jpg

post-6208-0-22053500-1366311594_thumb.jpg

After cleaning, they often feel unnaturally smooth in the hand… far smoother than you get from normal water polishing, as a result of the
combination of abrasive and chemical polishing.



Roger

I keep six honest serving-men (they taught me all I knew);Their names are What and Why and When and How and Where and Who [Rudyard Kipling]

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Thank you very much indeed ill be searching for more of the same this Saturday ill take some photos to show how they lay if i find any . Im still not totally convinced they are Gastroliths the stones ive found all ready but then again i dont see any reason why they cant be after taking on board the information im receiving so far... I seem to be covering most of the bases but its just not there yet.

Darren.

Regards.....D&E&i

The only certainty with fossil hunting is the uncertainty.

https://lnk.bio/Darren.Withers

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post-8873-0-70116200-1366320667_thumb.jpgpost-8873-0-70116200-1366320667_thumb.jpgD&E, thanks for starting this interesting post. It caused me to review the little I knew about gastroliths and to take a fresh look at the few I have. The photos you posted have a gastrolith "look" to my eye, but it's hard to judge that typical luster from a photo. Are you finding them in groups?

painshill, thanks for your informative post. It caused me to look at my pieces under my stereoscope for the first time! I did indeed find some long, straight, shallow scratches on one. Then I was delighted to spot this on the piece I posted above. To the naked eye it's about pinhead size. The gastrolith is Early Cretaceous, Cloverly Formation, Montana; but the formation/age of the original stone is of course, unknown.

I would be interested in everyone's opinion about this surprise.

Well, being ham-handed carried over from my prep efforts - I posted the same pic twice, sorry.

Human beings, who are almost unique in having the ability to learn from the experience of others, also are remarkable for their apparent disinclination to do so. - Douglas Adams, Last Chance to See

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attachicon.gifIMG_7044az.jpgattachicon.gifIMG_7044az.jpg

...I was delighted to spot this on the piece I posted above. To the naked eye it's about pinhead size. The gastrolith is Early Cretaceous, Cloverly Formation, Montana; but the formation/age of the original stone is of course, unknown.

I would be interested in everyone's opinion about this surprise...

To me, it resembles a foram.

"There has been an alarming increase in the number of things I know nothing about." - Ashleigh Ellwood Brilliant

“Try to learn something about everything and everything about something.” - Thomas Henry Huxley

>Paleontology is an evolving science.

>May your wonders never cease!

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Really enjoying this topic myself its something a bit different and very refreshing....im also trying to find a way of telling the geology of the stomach stones just to see if its possible to locate there hunting grounds.

Darren.

Regards.....D&E&i

The only certainty with fossil hunting is the uncertainty.

https://lnk.bio/Darren.Withers

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You may be interested in this paper by Oliver Wings. He concludes that ballast provided by swallowed stones is of limited importance for buoyancy in aquatic animals and suggests other functions: mineral supply and storage, stomach cleaning, maintenance of beneficial microbial gut flora, destruction of parasites and alleviation of hunger. Accidental ingestion of sediment, either by being mistaken for prey, by being attached to it, during playing, or due to pathological behaviour, is considered to be common.

Gastrolith Function - Review.pdf

(Love that fossil inclusion snolly)



Roger

I keep six honest serving-men (they taught me all I knew);Their names are What and Why and When and How and Where and Who [Rudyard Kipling]

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Thank you for the file there’s a lot of information there very useful I have another theory of which imp trying to shed some light on.
Gastroliths in Pliosaurs are a lot rarer than they are Plesiosaurs!...bearing that in mind I’ve also read that based on the size of the Gastroliths , palaeontologists can infer that some Pliosaurs could easily swallow some animals that were up to 6inches wide. Would anyone no if that were the case perhaps Pliosaurs relied more on chemical digestion than stomach stones enabling them to swallow prey whole!


Darren.

Regards.....D&E&i

The only certainty with fossil hunting is the uncertainty.

https://lnk.bio/Darren.Withers

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Another interesting theroy from someone I know was might have the pliosaurs preyed upon other animals who themselves used stone aid digestion methods.Resulting in the tranfer of stomach stones from one to another.

Anyone have any thoughts.

Darren.

Regards.....D&E&i

The only certainty with fossil hunting is the uncertainty.

https://lnk.bio/Darren.Withers

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Another interesting theroy from someone I know was might have the pliosaurs preyed upon other animals who themselves used stone aid digestion methods.Resulting in the tranfer of stomach stones from one to another.

Anyone have any thoughts.

Darren.

In the paper I attached, Oliver Wings rates both: "gastroliths attached to prey" and "prey contains gastroliths" as "plausible."

Roger

I keep six honest serving-men (they taught me all I knew);Their names are What and Why and When and How and Where and Who [Rudyard Kipling]

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  • 4 years later...

Again with the wonderful.

I think this is a very interesting subject.

Very informative. Thanks Roger.

I will definitely dig out my smallest and some others, I have identified, plus something 

other than.

Is there any reason to believe that some of the stones, when they got small enough,

would pass on through the digestive system? Thus being expelled along with the.........well you know.

 

Jess B

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