Thalassinidea 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. There are believed to be 556 extant species of thalassinideans in 96 genera, with the greatest diversity in the tropics, although with some species reaching latitudes above 60° north. About 95% of species live in shallow water, with only three taxa living below 2000 m. Ghost shrimp are an excellent food source for many types of both freshwater and saltwater fish. They are great for getting hard to feed fish to begin eating.