fossil in fossil

[Rockwood]

This is from the southwest side of the York river a short way upstream from the bridge in Yorktown, VA. And I do mean up, stream. The bank is rip rap !

Something appears to have settled on this bryozoan while it was alive ?

Scale is in mm. 

[fossilnut]

That is not depressing at all! It is very cool even if I don't have a clue what the critter was. Great find. Thanks for sharing.

[Rob Russell]

This area makes me think brachiopod. 

[Misha]

I don't think this is a brachiopid, from what I have read, the York river seems fairly recent in age and Brachiopods are not very numerous after the K-PG extinction.

I believe this is a bivalve, by the shape I would guess that it is a scallop, which would make sense since they can swim around and are not as stationary as other shells may be which is why it could have left that mark there before going off to a new location, or maybe the shell just broke off from the rest.

It would be nice to have a picture looking directly down at the impression though, to confirm my suspicion.

[Pagurus]

Maybe the bryozoan grew on and partly around the dead (or living?) shell of a bivalve?

[Rockwood]

8 hours ago, Misha said:

I believe this is a bivalve, by the shape I would guess that it is a scallop,

I just got out a scallop shell this size. The hinge line does have a groove that could become sectioned to look like the lines to the lower right. 

I think such a shell, convex side down, and sectioned by erosion of the contact surface might look just about like this. It would most likely have been disarticulated and deposited by current to allow the necessary time.

Poor little zooids. (Alright everybody, on three, lift and push.)