Pinnotheridae

See text Pinnotheridae is a family of tiny soft-bodied crabs that live commensally in the mantles of certain bivalve molluscs and the occasional large gastropod mollusc species in genera such as Strombus and Haliotis.

Tunicotheres moseri is commensal with a tunicate.

[1] The earliest fossils attributable to the Pinnotheridae date from the Danian.

[2] The following genera are recognised in the family Pinnotheridae:[3]

A pea crab (exact genus and species unknown) above the plate of mussels it was found in
A yellow pea crab (exact genus and species unknown) has fallen out of the clam this sea otter is eating, and has landed on the sea otter's neck (in Moss Landing , California )