Spiny Mollusk?

[Mochaccino]

Hi,

 

Anyone know what this is? Sorry have no info on it, not even provenance. No scale but based on the coin seems to be on the order of 10cm or less.

 

Thanks.

 

 

 

[fifbrindacier]

Hi, that look to be some kind of Oyster, maybe a Rastellum but more probably an Actinostreon (also called Lopha).

Edited January 29, 2023 by fifbrindacier

[Ludwigia]

I'll go for Actinostreon.

[Rockwood]

Likely from a formation in the Western Interior Seaway ?

[fifbrindacier]

Here is an Actinostreon i found, it's Kimmeridgian, so, upper Jurassic (Malm). Their range of period is wide, they appeared during the Triassic and still exist.

http://www.thefossilforum.com/index.php?/topic/73304-what-actinostreon/

Edited January 29, 2023 by fifbrindacier

[Mochaccino]

1 hour ago, fifbrindacier said:

Hi, that look to be some kind of Oyster, maybe a Rastellum but more probably an Actinostreon (also called Lopha).

 

1 hour ago, Ludwigia said:

I'll go for Actinostreon.

 

1 hour ago, Rockwood said:

Likely from a formation in the Western Interior Seaway ?

 

1 hour ago, fifbrindacier said:

Here is an Actinostreon i fond, it's Kimmeridgian, so, upper Jurassic (Malm). Their range of period is wide, they appeared d'urine the Triassic still exist.

http://www.thefossilforum.com/index.php?/topic/73304-what-actinostreon/

Thank you all, this definitely seems like a match. I suppose those parts I perceived as spines are a result of incomplete prep or preservation.

[fifbrindacier]

42 minutes ago, Mochaccino said:

 

 

 

Thank you all, this definitely seems like a match. I suppose those parts I perceived as spines are a result of incomplete prep or preservation.

Yes, it's because most of the fossil is still covered by the matrix. Only the ribs are visible.