Systematic Paleontology, Diversity Changes And Biostratigraphy Of Ordovician Bryozoans From The Tarim Basin, Xinjiang, China

Bryozoans are one of the most important group of Paleozoic fauna. Given their advantages on the well preservation and clear structure, Bryozoans can be used in stratigraphic division and correlation. Bryozoans were one of the main invertebrate groups dominating the Ordovician sea. The Ordovician bryozoans from the Tazhong and Tabei platforms in the Tarim Basin have received much less attention up to date, in contrast to their abundant occurrences in the Upper Ordovician carbonate units. This study systematically describes the bryozoans, summarizes their stratigraphical distribution and bryozoans assemblages characteristics.In the present study,29 species belonging to 23 genera in 10 families were identified:Prasoporu grayae Nicholson et Etheridge, Atactoporella declivis (Hu), Peronopora sp., Mesotrypa angularis Ulrich and Bassler, Dekayia sp., Batostoma inrebescens Bork et Perry, B. sp.l, B. sp.2, B. sp.3, Eridotrypa sp., Bythopora sp., Amplexopora minnesotensis (Ulrich), Leptotrypa sp., Hallopora elegantula (Hall), H. incontroversa (Ulrich), Diplotrypa catenulata Coryell, Lunaferamita nevadensis Utgaard, L. vesicularis sp.nov., L. sp., Graptodictya meneghinii (Vinassa de Regny), Chazydictya sp., Rhinidictya nicholsoni Ulrich, Metadictya crassa (Hall), Trigonodictya acuta (Hall), Stictoporella sp., Chasmatopora spatiosa Ariunchimeg, Ralfinella sp., Moyerella sp.,Moorephylloporina sp.. Among them, the finding of L. vesicularis sp.nov. extends the geographical and stratigraphical distributions of genus Lunaferamita.6 bryozoans assemblages were recognized for the first time from the Ordovician in the Tarim Basin. The assemblages include:1) unidentified cryptostomida assemblages; 2)Eridotrypa sp.-Bythopora sp. Assemblages; 3)Amplexopora minnesotensis－Rhinidictya nicholsoni assemblages; A)Prasopora grayae-Moorephylloporina sp. assemblages.5)Hallopora elegantula-Trigonodictya acuta assemblages.6) Atactoporella-Lunaferamita -stictoporella assemblages. They can be used in stratigraphic division and palaeobiogeographic correlation.