Ancient clades with restricted geographic distributions have been found in the isopod crustacean suborder Phreatoicidea. These isopods colonized fresh water in Gondwana by the Triassic Era and today are restricted to permanent groundwaters. A phylogenetic analysis of 21 exemplar species showed that major cladogenic events took place prior to the fragmentation of Gondwana. Nichollsia, a genus restricted to India, was deeply nested within a Western Australian and Victorian clade. The Phreatoicidae branched off early in all cladograms, with Australian and New Zealand sister clades. Some clades may be closely associated with Gondwanan landmasses that were subdivided by shallow Cretaceous seas.