Vulcanspotter Posted July 30 Share Posted July 30 Found a rounded polished stone at a local quarry in Faringdon Oxfordshire, Faringdon sponge gravels.You can find Plesiosaur and Croc at this location. Could this stone possibly be a stomach stone or its just a nice rounded stone? Link to post Share on other sites
TqB Posted July 30 Share Posted July 30 (edited) Welcome to the forum. Pebbles are frequent in these beds so it's probably impossible to ID gastroliths. Edited July 30 by TqB 1 2 Link to post Share on other sites
Mahnmut Posted July 30 Share Posted July 30 Hello and welcome to the forum! The answer to your question as you put it "could it possibly be" would be "yes, it possibly could" imho. If it was found in marine sediment, far from other pebbles (or even better, in a small cluster of pebbles in an otherwise pebble-free area) and relatively close to a reptile fossil site, I personally would gauge the probability relatively high. Without direct association to a skeleton there is no certainty though. I do not know if microscopically gastrolith surfaces could be discerned from other kinds of wear. I once found a pebble with what I saw as unusual gastrolith like sheen at Vache Noire, a famous french fossil site. I took it to the local museum and asked if they thought it could be a gastrolith. Retrospectively the guy on duty was the wrong one to ask, because he told me that only terrestrial herbivorous dinosaurs had gastroliths, which I now know to be wrong. On the other hand, my example was found at a pebble beach, so chances where quite low anyway. Best Regards, J 2 1 Link to post Share on other sites
pachy-pleuro-whatnot-odon Posted July 30 Share Posted July 30 He there and welcome to the forum! You'll find that we've got a lot of knowledgable members here, so you brought your question to the right place. Unfortunately, though, this is also a rather tricky question to answer. Because, as Tarquin said, the beds this pebble comes from regularly contains pebbles, making it harder to distinguish a natural one from a gastrolith, except for direct association with the gastral area of a marine reptile skeleton, as Jan suggested. That having been said, the way dinosaur gastroliths are identified on the Isle of Wight, where the beaches dinosaur fossils are found on are pebble beaches as well, is that the source rock of the pebble should be foreign to the area. In other words, if the petrological origin of the pebble doesn't correspond with a local source, something must've brought it there, with the explanation given it being a gastrolith. Another interesting approach to identifying gastroliths from regular pebbles is explained in the post below: The logic here is that if a pebble would've been smoothed due to fluvial action in a river, both the high and low relief points of the pebble would've become smoothed. However, in gastroliths, the low relief points would not have been smoothed, as the method of smoothing is much like that of pebbles in a rock tumbler, where only high-relief points are hit and subsequently smoothed... I hope this helps... 3 Link to post Share on other sites
Vulcanspotter Posted July 30 Author Share Posted July 30 Thanks everyone looks like just a smooth pebble then. Still I found a nice button tooth and a small rolled ammonite from the Kimmeridge layer. 1 Link to post Share on other sites
pachy-pleuro-whatnot-odon Posted July 30 Share Posted July 30 Photographs, or else it didn't happen Link to post Share on other sites
pachy-pleuro-whatnot-odon Posted July 30 Share Posted July 30 Cool! Tiny but great specimens! Link to post Share on other sites
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