Warm-waterTcherskidiumfauna (Brachiopoda) in the Late Ordovician Northern Hemisphere of Laurentia and peri-Laurentia

AbstractThe Late Ordovician (late Katian)Tcherskidiumfauna consisted of large- and thick-shelled virgianid pentamerid brachiopods characterized by large and ribbed shells ofTcherskidiumandProconchidiumand usually associated withHolorhynchus,Deloprosopus, andEoconchidium. This unique fauna was widely distributed across several tectonic plates, largely confined to the paleoequatorial and especially the northern paleotropical zones, such as northern Laurentia, accretionary terranes of Alaska, Kolyma, Baltica, Siberia, Kazakh and adjacent terranes, and South China. In Laurentia, the eponymous genusTcherskidiumwas predominant in regions north of the paleoequator and, in sharp contrast, was absent south of the paleoequator. In this study,Tcherskidium lonein. sp. andProconchidium schleyin. sp. are described from Alaska and North Greenland, respectively, adding new data on theTcherskidiumfauna of the Late Ordovician Northern Hemisphere. Shell gigantism, together with the sharp paleobiogeographic division, suggests that the Late Ordovician (late Katian) Northern Hemisphere had a prevailing warm-water mass, probably due to the lack of large landmass beyond the northern tropics. This was in sharp contrast to the Southern Hemisphere, which was frequently influenced by cold-water invasions from the ice-bearing Gondwana supercontinent centered on the South Pole.UUID:http://www.zoobank.org/25d9b772-bd7d-4ad6-bfc6-ba02b1567cf3