mancos shale id help please

[ober]

This impression and partial exoskeleton is slightly larger than a postage stamp. It is from a Mancos shale deposit outside of Moab, between the city and Rt 70. I’m unsure of the words to use, but it looks like there was a central back carpace with a skirt around it. ID help much appreciated. Thank you.

[Darktooth]

I am thinking possibly a bi-valve of some sort? 

[Bronzviking]

Welcome to the Forum from Florida. I'm not familiar with your deposit. What state and part of the state was it found? (ex, SW Florida) I agree with Darktooth, it looks like a right and left valve of an eroded shell showing the hinge in the middle.

[ober]

Thank you for looking. It is from outside Moab in Utah, on BLM land. The Utah Roadside Geology book ID's this as Cretaceous and a local referred to it as Mancos shale.

[ober]

here is another picture. it looks like above what might be a back carpace is a smaller element that might be a head. Would a bi-valve have that type of center carpace type  element?we are looking at this fro. the under side. 

[ynot]

This is the shell of a clam (bivalve) that has partly eroded away. The hinge is in the middle and You can see both shells (sides of the clam).

It is not a "carapace" of any type.

[ober]

thank you for taking a look and id-ing this. 

[Bronzviking]

Here's an example of a butterflied seashell bivalve.

[ober]

oh, this is helpful. thanks. i didn’t see this in my fossil.

[abyssunder]

Probably you call the valves  - "carapaces".
What you have is the inside of a bivalve with the valves opened out.

This is how a bivalve may look with closed valves seen from exterior:

 

picture from here

[Fossildude19]

Maybe @PFOOLEY will have some ideas, although bivalve is looking good.  

 

[ober]

This diagram is very helpful and allows me to see how this can be a bivalve. It also clarifies what a bivalve is, in what are the 'bi' parts. Thanks for your post.

[PFOOLEY]

@ober, compare your specimen with the genus Mytiloides.

[ober]

Thank you. You suggestion led me to a number of new to me sites, including the cretaceous atlas of ancient life. This helped me identify a number of other unknowns I have. I appreciate your response.