Bivalve or Brachiopod -- or Gastropod!? (Driveway gravel find, possibly Mississippian)

[icycatelf]

The seashell fossils I usually find in the driveway gravel (not local) are brachiopods, but this one is larger (almost 3cm long), seems more oblong, and the umbo(?) is more curled. Based on the image results, I'm leaning toward bivalve, but I'm not confident about it.

The humidity is fogging up my lens, preventing me from taking the photos outside. Please bear with the quality. (EDIT: Better pics in post #8.)

Edited July 5, 2016 by icycatelf

[BobWill]

Bivalve, I would say oyster.

[MeargleSchmeargl]

Bivalve, I would say oyster.

I agree.

[Guguita2104]

I agree with oyster bivalve.

Regards,

[RockSmith]

Nice little "Devils Toenail" as we call them in Central Texas, or Gryphaea. Good find for a driveway!

[MeargleSchmeargl]

Nice little "Devils Toenail" as we call them in Central Texas, or Gryphaea. Good find for a driveway!

Confirmed. The specimen does indeed match Gryphaea.

[FossilDAWG]

I am not convinced it is a bivalve. I can think of several brachiopods that would also look like this. If the gravel usually yields brachiopods, it is unlikely that the source would be Cretaceous and it is unlikely that the fossil is a Gryphea ("devil's toenails"). Can we see a photo that clearly shows the umbo/"beak" area? It looks as if it would be easy to remove more of the matrix and expose the shell better, which would be helpful.

Don

[icycatelf]

Here are some better-quality pics, including a better shot of the umbo:

Edited July 4, 2016 by icycatelf

[tmaier]

Bilateral symmetry, classic "lamp shell" shape... looks kind of brachiopodish to me.

[Herb]

looks like a Mississippian Platyceras sp. to me. There are no Cretaceous fossils in Kentucky

Edited July 4, 2016 by Herb

[icycatelf]

I see a resemblance to Platyceras, but isn't it a little too flat to be one? Also, the end doesn't look quite as curly as Gryphaea (and, again, it looks a little too flat).

This picture is making me lean toward brachiopod:
http://jurassiccoast.org/fossilfinder/wp-content/uploads/sites/2/2015/09/2_Brachiopod_A_copyright_Nicholls_2014_904x478.jpg

Edited July 4, 2016 by icycatelf

[Herb]

Platyceras' are often flat in the Miss. of KY. Where did you find it (town)

Edited July 4, 2016 by Herb

[icycatelf]

Platyceras' are often flat in the Miss. of KY. Where did you find it (town)

I found it in Whitehouse (Johnson County), but the gravel was brought in from elsewhere. howard_l once mentioned that they came from the Slade formation.

[BobWill]

If you want a better ID than bivalve or brachiopod you'll need to try to knock the matrix off of there for a better look at the rest of it. Since it's just driveway gravel and you're not sure about the source it won't matter if it gets damaged in the process.

[Herb]

Looks like you are in a Miss. or Penn. strata area. The tiny bit of Cretaceous in western KY (land between the lakes area) has no fossils

[howard_l]

I think Herb may have it. Here are some Platyceras from Mississippian age from various locations near Kentucky the last one I found in Meniffee Co. In the Nada.

[icycatelf]

Not sure if it'll help with the ID, but did anyone else notice the crease at the end? (Runs the opposite direction of the texture lines.)

Edited July 5, 2016 by icycatelf

[BobWill]

Not sure if it helps either. How about an end view to show it better? The lines forming the texture are called growth lines and represent each new layer of shell material laid down on the inside of each valve. As the body grows and needs more space each new layer extends out a little farther than the last. Some bivalves and brachiopods also have ornamental lines either paralleling or crossing the growth lines.

[icycatelf]

Posterior view (animated to show the crease):

[BobWill]

Thanks for the new view. That interruption in symmetry should convince everyone that Herb is right.

[icycatelf]

Anymore opinions?

[Fossildude19]

Gastropod is a good bet, I think.

Looks a bit too smooth to be a horn coral.

Don't think bivalve or brachiopod, either.

Regards,