RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 11, 2021 9:27:49 GMT -5
RWA3006 Here's an interesting article on marine gastroliths. Stomach Stones for Feeding or Buoyancy? The Occurrence and Function of Gastroliths in Marine Tetrapods www.jstor.org/stable/55808?seq=1Gastroliths or `stomach stones' occur frequently in some, but not all, groups of fossil and living marine tetrapods. Comparative analysis of gastrolith distribution suggests a role in buoyancy control rather than food processing. Once accidental ingestion by bottom-feeding animals is excluded, gastroliths occur in most tetrapods which `fly' underwater with hydrofoil limbs, including plesiosaurs, penguins, and otariid pinnipeds, but not the marine chelonians. They do not usually occur in cetaceans, ichthyosaurs, mosasaurs, and odobenid and phocid pinnipeds, which swim with a caudal fin or the equivalent. Occurrence in amphibious forms is variable; crocodilians often have gastroliths, but nothosaurs and placodonts do not. The correlation of gastroliths and underwater flight is corroborated by a comparative analysis which takes phylogenetic factors into account. There is no correlation with diet. Consideration of function and occurrence in terrestrial forms suggests that the use of gastroliths in digestion would not be useful, and might even be harmful, to a carnivorous marine tetrapod. Gastroliths are more efficient than skeletal bone (as in pachyostosis) in terms of sinking force per unit of added mass or volume. As well as driftwood and ice, marine tetrapods should be considered as a potential source of erratic stones in freshwater and marine sediments. Gastroliths may have evolved by the accidental ingestion of stones, the retention into adulthood of stones used by juveniles to process insect or plant food, or as a compensatory replacement for dense bones habitually filling the stomach. Their presence or absence should be more carefully recorded and further studies should be carried out on their function. Rick, I wasn't aware of this and it reinforces my impression that there is so much that we don't know. Thanks.
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 11, 2021 9:31:25 GMT -5
|
|
|
Post by 1dave on Jan 11, 2021 10:07:50 GMT -5
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 12, 2021 8:00:47 GMT -5
TURD TUESDAY
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 13, 2021 16:45:35 GMT -5
Here's more pellet conglomerate specimens.
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 13, 2021 16:48:33 GMT -5
|
|
|
Post by jasoninsd on Jan 13, 2021 19:09:16 GMT -5
Randy, I've got to ask to figure out if I'm learning anything here on RTH...the white spots...they're agotized, correct?
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 13, 2021 23:11:59 GMT -5
jasoninsd yes, the whole thing is highly agatized. I've noticed the white turns more clear/blue/translucent when it's cut or polished just like many other agates. They remind me of the white rind on many Montana agates. I suppose some kind of surface oxidation is in play here. I've noticed a phenomenon where the outer crust, perhaps a quarter inch is sometimes not very agatized and gets worn off easier leaving tough agate formations standing proud. Once you get through that crust the whole thing seems to be uniformly agatized except for occasional pockets of crumbly material that never solidified. Usually they are tough agate through and through.
|
|
|
Post by jasoninsd on Jan 13, 2021 23:20:52 GMT -5
jasoninsd yes, the whole thing is highly agatized. I've noticed the white turns more clear/blue/translucent when it's cut or polished just like many other agates. They remind me of the white rind on many Montana agates. I suppose some kind of surface oxidation is in play here. I've noticed a phenomenon where the outer crust, perhaps a quarter inch is sometimes not very agatized and gets worn off easier leaving tough agate formations standing proud. Once you get through that crust the whole thing seems to be uniformly agatized except for occasional pockets of crumbly material that never solidified. Usually they are tough agate through and through. Holy crap, I am learning something on here! Whoot Whoot! Hmmmm... Brazilian Agates, White-skinned Agates, and Black-skinned Agates (I'm sure there are way more) have a "similar" rind to them as well. I'm probably stretching for similarities...but I wonder if the agotization process results in the similar exteriors...
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 14, 2021 8:02:44 GMT -5
jasoninsd yes, the whole thing is highly agatized. I've noticed the white turns more clear/blue/translucent when it's cut or polished just like many other agates. They remind me of the white rind on many Montana agates. I suppose some kind of surface oxidation is in play here. I've noticed a phenomenon where the outer crust, perhaps a quarter inch is sometimes not very agatized and gets worn off easier leaving tough agate formations standing proud. Once you get through that crust the whole thing seems to be uniformly agatized except for occasional pockets of crumbly material that never solidified. Usually they are tough agate through and through. Holy crap, I am learning something on here! Whoot Whoot! Hmmmm... Brazilian Agates, White-skinned Agates, and Black-skinned Agates (I'm sure there are way more) have a "similar" rind to them as well. I'm probably stretching for similarities...but I wonder if the agotization process results in the similar exteriors... I like to hunt moss agate in southwestern Wyoming and much of what I find has a milky white surface layer that usually goes about a thirty second of an inch deep until it clears into the translucent blue I'm so fond of.
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 19, 2021 7:44:06 GMT -5
TURD TUESDAY
|
|
|
Post by RickB on Jan 19, 2021 8:23:42 GMT -5
Who flung dung?
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 19, 2021 9:43:14 GMT -5
Looks just like a cow patty laying there doesn't it?
|
|
Brian
fully equipped rock polisher
Member since July 2020
Posts: 1,512
|
Post by Brian on Jan 19, 2021 9:49:31 GMT -5
Looks just like a cow patty laying there doesn't it? I thought my eyes were playing tricks on me with that one. It does look like it is relatively fresh.
|
|
|
Post by 1dave on Jan 19, 2021 10:16:33 GMT -5
Looks just like a cow patty laying there doesn't it?
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 19, 2021 11:08:51 GMT -5
Looks just like a cow patty laying there doesn't it? I thought my eyes were playing tricks on me with that one. It does look like it is relatively fresh. Erosion might have uncovered it anywhere from five to 100 years ago. There hasn't been a good gully washer in the area for at least five years now.
|
|
Brian
fully equipped rock polisher
Member since July 2020
Posts: 1,512
|
Post by Brian on Jan 19, 2021 20:57:49 GMT -5
I thought my eyes were playing tricks on me with that one. It does look like it is relatively fresh. Erosion might have uncovered it anywhere from five to 100 years ago. There hasn't been a good gully washer in the area for at least five years now. And now I have a mental image of Hercules diverting rivers to clean the coprolites of the Augean stables.
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 19, 2021 21:13:52 GMT -5
This chasm cuts right through coprolite country.
|
|
|
Post by woodman on Jan 19, 2021 22:16:54 GMT -5
This chasm cuts right through coprolite country. It would great fun to wander thru this country!
|
|
RWA3006
Cave Dweller
Member since March 2009
Posts: 4,578
|
Post by RWA3006 on Jan 19, 2021 22:35:11 GMT -5
This chasm cuts right through coprolite country. It would great fun to wander thru this country! It is, and I can't get enough of it, but not in June through August because of the heat. The area is so vast and three dimensional from rough topography that it would take many lifetimes to learn it all. A guy on horseback could penetrate a lot of it, but much is too rough for even hiking. The allure is intoxicating.
|
|