Unknown fossil carboniferous

[patrick plesiosaurus]

Here is a fossil I found in some carboniferous limestone. 

 

Does anyone know what it is. 

 

It was found in the limestone of the berwick upon tweed area N england. 

[Tidgy's Dad]

Fragment of a brachiopod valve, I should think. 

[patrick plesiosaurus]

How have you come to that conclusion. 

 

It is 2D and shows no curvature like a bivalve would (should). 

[Rockwood]

1 hour ago, patrick plesiosaurus said:

It is 2D and shows no curvature like a bivalve would (should).

The dimensionality of it seems to me to be demonstrated by comparison to the crinoid columnal adjacent to it in my view. 

Fin rays tend to look more segmented and the fin more film like in my experience as well.

A separate issue of taphonomic distortion would render a slight curvature issue moot even if curvature were mandatory in bivalves.

[Tidgy's Dad]

I didn't say it was a bivalve. I said it could be a bit of a brachiopod. 

Firstly, there seems to be a slight curve to the fragment, but that may just be the photos.

Secondly, many brachiopods have a flat valve or valves flat in parts. 

Thirdly, the costae resemble those of productid brachiopods from that age and region.

 

[patrick plesiosaurus]

Thank you very much. 

 

Yes I meant brachiopod sorry.