Carboniferous Shells in Shale

[Lucid_Bot]

Hi! I was collecting plant fossils and found these shells. They are Pennsylvanian (Carboniferous), Conemaugh Group, Glenshaw Formation. I don't know what they are. Any help is appreciated, thank you.

[connorp]

Nice finds. Probably either Dunbarella or Aviculopecten.

[abyssunder]

 

Dunbarella knighti from the Dennis Limestone of Jackson County, Missouri (KUMIP 60458).

Dunbarella kni

Edited November 30, 2021 by abyssunder

[Jeffrey P]

Really nice preservation on those bivalves. Congrats. 

[FossilDAWG]

I'd also go with Dunbarella.  Aviculopecten would be more spiny.

 

Don

[westcoast]

+1 for Dunbarella

[cngodles]

 

15 hours ago, FossilDAWG said:

Aviculopecten would be more spiny

 

Not for Aviculopecten. I believe it's Acanthopecten that is spiny.. See plates 6, 7, and 8 here: https://kb.osu.edu/handle/1811/78537

That is if we are talking about the ventral margin.

 

But I agree, the wider fan appearance goes with Dunbarella best.

 

The Ohio book is a good reference for the Glenshaw Formation. Many of the specimens come from the same rock layers.

[FossilDAWG]

34 minutes ago, cngodles said:

Not for Aviculopecten. I believe it's Acanthopecten that is spiny.. See plates 6, 7, and 8 here: https://kb.osu.edu/handle/1811/78537

That is if we are talking about the ventral margin.

Oops, you right of course.

 

Still, the fossils in question are virtually identical to some Dunbarella I have from New Mexico, and they are quite different from the Aviculopecten I have collected/seen.

 

Don

[Missourian]

They seem to have the 'feel' of Dunbarella.

 

A way to tell the two apart is that Dunbarella is wider and lacks the pinch below the hinge of Aviculopecten. A little prep work could reveal this part of the shell a little better.

 

Plus, in my parts, these tend to occur in shale, while Aviculopecten seems to have an 'affinity' to limestone.

[Missourian]

For reference, a complete valve of Dunbarella (not my specimen):