Article: Biogeography of Permian ectoproct Bryozoa
Earliest Permian (Asselian and early Sakmarian) ectoprocts were widespread, included many lineages of Carboniferous origin, and had a large number of cosmopolitan genera. Marked geographic differences in their generic diversity suggest that physical parameters, such as temperature, were important factors in controlling ectoproct distributions. Late Sakmarian and Artinskian ectoprocts show a number of distribution patterns, as well as the beginning of a clearly defined Tethyan fauna with a number of endemic genera. During the Artinskian, Tethyan genera have greater dispersal so that certain areas, such as Australia and Pakistan, contain a number of Tethyan genera, whereas other areas, such as the Uralian and Franklinian regions, received only a few immigrant Tethyan genera.By the early part of the Kazanian, ectoprocts are strongly provincial with Tethyan faunas having both high diversity and endemism and non-Tethyan faunas having low diversity. Ectoprocts from Zechstein strata have unusually low diversity, perhaps because of major fluctuations in temperature or salinity, and Australian ectoprocts are also less diverse at this time. Dzhulfian ectoprocts are greatly reduced in generic diversity, geographic distribution, and in total numbers because many lineages become extinct near the middle of the Late Permian. Most ectoprocts of the late Dzhulfian are remnants of Tethyan endemic lineages and only a few genera survive into the earliest Triassic before becoming extinct.