Biodiversity and historical biogeography of stalked crinoids (Echinodermata) in the deep sea

About 95 species of stalked crinoids are now described from 60m to hadal depths, but our knowledge remains far from complete. Depending on which species concept is used, estimates of species richness can be dramatically different. It is necessary to have a homogeneous concept for taxonomic units. The abundance of the crinoid fossil record allows a discussion of the ancestry of deep sea crinoid fauna. Stalked crinoids have a horizontal diversity pattern with three regional centres of high diversity (i.e. western tropical Pacific, western tropical Atlantic and north-eastern Atlantic). Vertical patterns show two faunal strata which vary in importance among provinces. The epibathyal stratum has apparently remained relatively similar in intertropical areas since the Mesozoic. Despite environmental changes related to glaciation since the Middle Miocene, the deepest crinoid fauna (i.e. the deep sea fauna sensu stricto at depths more than 1000 ± 200 m) have a very ancient origin with a dispersion closely related to plate tectonics. The bathyal fauna on hard substrates includes a few living fossils and has a high historical interest.