Gastrolith In Coprolite?

[PiranhaPirate]

Hello All,

I found this unique rock/fossil specimen at a local consignment store. It didn't have any information associated with it. I thought it may be a gastrolith imbedded in a coprolite due to the size and shape of the stone and the layering of the rock around it - but I may be way off. I live in northern Florida so it may have come from somewhere in this region. I would greatly appreciate your help identifying it!

Weight: 170.4g or 6oz
Size: 62mm by 50mm (Just bigger than a golf ball)

Edited January 4, 2014 by PiranhaPirate

[Auspex]

What an interesting item! I see the layering to which you refer, but layering is not something I normally associate with coprolites, so I don't know what to make of it. In the hand, does the remarkable color of the core seem natural?

[Herb]

It appears to be a stone surrounded by a limy concretion a fairly common occurrence (Limy sea floor, current rolls a rock around and builds up layers of stone around it) especially in Neogene/Pleistocene environments. N.Florida is mostly Miocene or younger, so no dinosaurs. I don't know if ice age critters had gastroliths, so could be one. I know if it was mine I would break it out or dissolve the shell to see what's hidden. My best guess.

[PiranhaPirate]

Hello

Thanks for the response. I thought the black stone looked strange too. So I dipped the specimen into some acetone this afternoon and it came out looking completely different. I have attached some new pictures on my original posting. It also looks like someone coated it with a PVA substance which is now peeling off due to the acetone bath.

[PiranhaPirate]

Herb - Thanks for the info!

[painshill]

I would suspect that someone has painted a pebble in a calcareous concretion with black enamel paint to make it look more desirable/interesting than was the case!

Incidentally, gastroliths are by no means a palaeo-phenomenon. Modern birds with a mainly herbivorous diet – notably ostriches - swallow stones as a digestive aid and so do modern crocodiles, alligators and seals (presumed for buoyancy control).

[Herb]

Good to know.