Boreskov

PP‐26THE BIOGEOGRAPHICAL EVOLUTION OF THE PERMIAN AMMONOIDSLeonova T.B.Borissiak Paleontological Institute RAS, Moscow, RussiaThe Permian period was a time of global climatic turnover, when the cold icy climate ofthe Late Paleozoic was replaced by the ice‐free Mesozoic. The climate of the Early Permianshowed prolonged episodes of glaciations, which to a large extent determined the evolutionof the marine biota. The area covered by glaciers reached its maximum at the end of theLate Carboniferous‐beginning of the Early Permian. The first significant warming episodeoccurred in the second half of the Sakmarian‐beginning of the Artinskian. The second half ofthe Artinskian and Kungurian are considered as the warmest periods in the Early Permianepoch. The general regression of the Middle and Late Permian was complicated by smaller,relatively short‐term transgressive‐regressive cycles and warming and cooling episodes.The data on the generic and familial content of assemblages in all localities, endemicgenera, centers of diversification, and quantitative changes of the dynamics of genericchanges in ammonoid communities allow to the recognition of five large realms: Uralian,North American, Arctic, Australian, and Paleotethyan.The majority of all Permian genera are known from the Paleotethyan realms. At thebeginning of the Early Permian 45% of all genera known from this interval (a.g.)come fromthe Paleotethys. At the end of the Early Permian over 60 genera, or 80% a.g.; at thebeginning of the Middle Permian ‐ 78‐96% a.g., of these up to 60‐70% a.g.at various timeswere endemic. In the Late Permian ammonoids were preserved only in this Realm (100%a.g.).At the Uralian Realm three of the four typical Permian families appeared. At the Asselianand Sakmarian ammonoids constituted 71% and 61% a.g. The Early Artinskian ammonoidsare the most typical in this region (78% a.g.). In the Late Artinskian diversity of theseammonoids decreased to 45% a.g., and to 6% a.g. in the Kungurian.At the Arctic Realm (Northeastern Asia, Novaya Zemlya, Pai‐Khoy, Vaigach Island, Volga‐Urals, Canadian Arctic Archipelago, and Alaska) ammonoids were moderately diverse (22%a.g.in the Asselian, and 29% a.g. in the Sakmarian). There were fewer Early Artinskianammonoids (14% a.g.). In the Kungurian the extent of endemism also increased, i.e., of 10177