Molecular taxonomy and phylogenetic affinities of two groundwater amphipods, Crangonyx islandicus and Crymostygius thingvallensis, endemic to Iceland

► The taxonomic status of Crymostygius thingvallensis as a new family is confirmed. ► Crangonyx islandicus may represent a new genus. ► Molecular and morphological taxonomy show discrepancies and a taxonomic revision of the Crangonyctidae is needed. ► The family Crangonyctidae is monophyletic, supporting the occurrence of a widespread common ancestor before Laurasia break up around 60 Mya. ► Phylogeographic patterns indicate colonization of Iceland from the Nearctic via Greenland.