Wyoming Cretaceous Bivalve

[ClearLake]

A while back I collected a group of bivalves from the Frontier Formation (Cretaceous) just south of Kemmerer (Lincoln County) Wyoming and I am having  some trouble pinning down an ID.   The formation is known for containing Crassostrea soleniscus and Inoceramus, but these are neither of those.  Based on my Texas Cretaceous Bivalves book, they could be some species of Panopea but I am not at all certain of that.  Unfortunately, although I have quite a number of samples, there aren't any that expose the dentition so that is a bit of a disadvantage.  I'm hoping one of our Wyoming experts and/or bivalve experts have seen these before as I'm pretty sure they are not uncommon.  My internet searches have failed me so far.  Or if anyone can suggest  a good literature source for Wyoming Cretaceous bivalves, I am happy to to do some reading and deciphering.  Thanks very much for any help you can provide.  The first two pictures are two views of the same specimen, the third picture is a seperate one.

 

 

[jpc]

I like to think that I am one of those Wyoming experts you mentioned, but bivalves are beyond me.  I agree that it is not an Inoceramid.  

[Thomas.Dodson]

I don't think they're Panopea. Looks like a Legumen sp. I see both Legumen ellipticum and indet. Legumen sp. are reported from the Frontier Formation in Northern Wyoming. Legumen ellipticum looks more, well, elliptical so this is probably one of those undescribed Legumen sp.

 

Outcrop Descriptions and Fossils from the Upper Cretaceous Frontier Formation, Wind River Basin and Adjacent Areas, Wyoming

[ClearLake]

@jpc  Well, yes, you were one of the ones I was hoping might know.  But I understand that bivalves are not everyone cup of tea.  Thanks for looking.

 

@Thomas.Dodson  Thanks for the link.  I had found a similar publication by the same author on the Big Horn Basin, but it only listed the diagnostic fossils at each site.  The one you linked has longer lists of fossils.  Legumen was another genus I considered and may be it, although I do see Panopea also listed at one of the localities.  I will do some more research into the differences and look at the other potential (if any) genera from the publication.  One of the key distinguishing factors appears to be the dentition, which is not exposed in any of my specimens.  Maybe if I do a little prepping I might be able to see something.  Of course if I could see an obvious gape, or lack of it, that  would also help to include or rule out Panopea.  Again, thanks for the suggestions, I'll dig into that some more.

[Jeffrey P]

I have two different species of Legumen from the Upper Cretaceous of New Jersey, (two different formations) both of which resemble your specimen. I have a number of specimens of Panopea and I can assure you yours clearly is not that.  

[ClearLake]

@Jeffrey Pthanks, that seems like the best answer and is helpful because the couple of specimens I have found in the literature from the mid continent region are pretty poorly preserved.