Thalassiniea is an infraorder of decapod crustaceans that live in burrows in muddy bottoms of the world's oceans. They are poorly known to most people, and as such have few vernacular names - "mud lobster" and "ghost shrimp" counting among them. Recent molecular analyses have shown this group to be most closely related to Brachyura (crabs) and Anomura (hermit crabs and their allies). The fossil record of thalassinideans reaches back to the late Jurassic.