Mesozoic-cenozoic crustaceans preserved within echinoid tests and bivalve shells

Abstract

Associations of crustaceans with echinoids (Echinodermata) and bivalves (Mollusca) are not uncommon in modern oceans. Here we record the occurrence of anomurans, brachyurans and isopods within echinoid tests and bivalve shells from the Middle Jurassic of France, the Upper Jurassic of the Czech Republic, the Eocene of Croatia and the Miocene of Austria. Additionally a new genus and species of fossil cirolanid isopod from the Middle Jurassic of France is described. The present examples are interpreted as crustacean sheltering, probably for safe and undisturbed moulting (ecdysis), within a vacant host test or shell. However, accidental association (washed in) or even food remains cannot be ruled out entirely.