The Pylochelidae are a family of hermit crabs. Its members are commonly called the 'symmetrical hermit crabs'. They live in all the world's oceans, except the Arctic and the Antarctic, at depths of . Due to their cryptic nature and relative scarcity, only around 60 specimens had been collected before 1987, when a monograph was published detailing a further 400.
Description Unlike other hermit crabs, pylochelid hermit crabs are not markedly asymmetrical, with a straight body and equal numbers of appendages on both sides. This characteristic, together with the partial calcification of the abdomen (which is soft in other hermit crabs) led Edward J. Miers, when describing the first species, to consider it to represent a transition between hermit crabs and "Macrura" (long-tailed decapods, such as lobsters and shrimp). Correspondingly, pylochelid hermit crabs do not usually inhabit gastropod shells, but instead withdraw into decayed pieces of wood, stones, tusk shells (especially Dentaliidae), living sponges, pieces of bamboo or mangroves. Their claws are often adapted to form an operculum, which closes off the entrance to their home.
Distribution Although the family as a whole has a global distribution, diversity is concentrated in the Indo-Pacific, with only four species being found in the western Atlantic Ocean and Caribbean Sea (Cheiroplatea scutata, Pylocheles agassizii, Bathycheles cubensis and Mixtopagurus paradoxus). Pylochelid hermit crabs inhabit a great range in water depths, from , with most living between deep.
Genera The family contains 48 species in 12 genera: Bathycheles – six species Cancellocheles – one species Cheiroplatea – six species †Cretatrizocheles – one species Forestocheles – one species †Mesoparapylocheles - six species Mixtopagurus – one species Parapylocheles - one species Pomatocheles – three species Pylocheles – two species Trizocheles – eighteen species Xylocheles – two species
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