Biogeographical and paleobiogeographical problems in Stenasellids (Crustacea Isopoda Asellota of underground waters)

Considering their systematic isolation among present Asellota, their strong burrowing behaviour, their aptitude for interstitial life and their wide north-tropical present distribution, the history of Stenasellid Crustaceans seems to be marked by the antiquity of their settlements in continental groundwaters (Middle Cretaceous period?) and a long stage of life in phreatic waters on permanently emerged paleotropical continents during the Cenozoic Era. The resemblance between some forms of the Guinean shield and Mexico sets the problem of the anteriority of their continental conquest to South Atlantic drift. The repartition of Mediterranean European forms appears as a consequence of paleogeographical changes in Tertiary Times. The distribution of continental European forms has been marked by Quaternary climatic alterations: severe curtailment of settlements, endemicity in Glacial periods but wide Holocene expansion for the forms adapted to new climatic conditions