Продолжительность существования и скорость образования видов и родов двустворчатых моллюсков в перми Северо-Востока Азии

The article discussed the duration of existence and the rate of formation for Permian bivalve species and genera in Northeast Asia. It has been established that the species existed averagely for 2-5 million years; and the genera, for 10-20 million years. The vast majority of long-lived taxa characterize the Early Permian (Asselian-Middle Artinskian) assemblages. The proportion of long-lived species that existed for over 10 million years exceeds 25 % of all bivalve species existing on this stage. Since the end of the Artinskian (and even more so since the Kungurian), the number of relatively short-lived species increased significantly. The possible reason for this phenomenon might have been an increase in the frequency of manifestation of geobiospheric, mainly extinction (Biakov, 2012a), events, resulted from an increase in the Earth endogenous activity, and expressed in the manifestation of volcanic activity of various nature and the deep fluids impact on the biota. A long time interval, covering almost the entire Lower Permian and characterized by a relatively calm course of geological history, was replaced by an interval with sharp upheavals manifested, which also affected the development of the entire biota, including bivalves. The rate of taxa formation is also associated with geobiospheric events and is controlled primarily by extinction events.