Biochronology of Triassic bivalves

摘要: Substantial advances by numerous researchers over the past 20 years have made it possible to develop a composite biochronological scheme for Triassic based on bivalves Claraia, Peribositria, Enteropleura, Daonella, Halobia, Eomonotis and Monotis. These exhibit temporal durations nearly equal ammonoids conodonts. Widely distributed across Tethys, Panthalassa Boreal regions, these occur in wide variety of marine facies water depths, but are most notable their thick shell accumulation deeper-water oxygen deficient environments. They were likely resting or reclining benthos, may housed chemosymbionts, part episodic opportunistic palaeocommunities near settings. A new zonation is presented that encompasses entire integrated with standard ammonoid schemes. The Lower characterized 2-3 zones notably from eastern Tethys representing Induan lower portion Olenekian. Later Olenekian, realm, species Peribositria (included some workers within Bositra) provide useful zonal indexes. Middle well represented Enteropleura (Middle Anisian) Daonella (Upper Anisian through Ladinian) North America significant occurrences through- out circum-Pacific realms. Upper can be subdivided into 8-13 bivalve succession Monotis sensu lato best representation regions.