Bivalve from Cap-Gris-Nez

[Max-fossils]

Hi all,

 

Wondering what bivalve species this is. Found at Cap-Gris-Nez, France. From the Jurassic. 

Looks like it may be a Pholadomya species to me? Not sure...

 

Thanks in advance,

 

Max

 

[Max-fossils]

This block was found not too far away and seems to contain the same species (but in lesser condition / with more matrix still on it)

[Tidgy's Dad]

Yes, Pholadomya, but there are so many species i can't say which one for sure, but maybe,just maybe P. protei? 

[Max-fossils]

1 hour ago, Tidgy's Dad said:

Yes, Pholadomya, but there are so many species i can't say which one for sure, but maybe,just maybe P. protei? 

Time period does seem to fit, but the few images I am seeing online of the species aren't very well-matching...

 

But still thank you Adam!

 

[Tidgy's Dad]

Just now, Max-fossils said:

Time period does seem to fit, but the few images I am seeing online of the species aren't very well-matching...

 

But still thank you Adam!

 

It's a very variable species, but i'm far from certain! 

 

[Ludwigia]

It's a Pholadomya alright. Perhaps P. fidicula. Could also be P. zietenii. They are both quite similar.

[Max-fossils]

12 hours ago, Tidgy's Dad said:

It's a very variable species, but i'm far from certain! 

 

Again, the ridges are concentric and not radial (kinda parallel to the umbo, and not perpendicular). Even though the ridges on mine are radial. 

And in bivalve ID that's a critical aspect which is definitely species-defining (well I've never heard of a bivalve species on which some specimens had concentric ridges and others radial ones...)

 

[Max-fossils]

12 hours ago, Ludwigia said:

It's a Pholadomya alright. Perhaps P. fidicula. Could also be P. zietenii. They are both quite similar.

Both seem like good matches, but I'm gonna go with Pholadomya fidicula. Appears to be from the Jurassic too, so that's good. 

The spacing between the radial ridges seems to match very well with mine, while P. zietenii (this is a picture of one of your specimens ) has its ridges more closely spaced:

 

I'm not finding much info on Pholadomya zietenii though... Where did you find the ID for your shell?

 

Thanks a lot for your help Roger!

[Ludwigia]

You're welcome.

[Max-fossils]

On 5/20/2018 at 11:12 AM, Max-fossils said:

I'm not finding much info on Pholadomya zietenii though... Where did you find the ID for your shell?

@Ludwigia 

?

Just out of curiosity  

[Ludwigia]

1 hour ago, Max-fossils said:

@Ludwigia 

?

Just out of curiosity  

I got the id from a paleontologist who specializes in bivalves.

[Max-fossils]

13 hours ago, Ludwigia said:

I got the id from a paleontologist who specializes in bivalves.

Ah ok