关键词: 中二叠世晚期, 腕足动物, 物种多样性, 演变, 重庆合川地区

Abstract:

Analysis of the evolution of species diversity based on brachiopod fossils of the Maokou Formation strata in the Hechuan area in Chongqing city indicates that the Lopingian Epoch incident in this region occurrs in the Late Permian. According to the integrated index of brachiopod species diversity  and the brachiopods evolutionary process, this paper concludes that the Lopingian Epoch incident in this region is composed of two phases. In the first phase， genus extinction rate was 42.9% and the species extinction rate was 60%. Rates of the second phase were 42.9% and 66.7% respectively. Before the both extinctions, two courses of expansion in species diversity occurred, and the coming probability of new species in the first course was 75%. Probability of new species in the second course was 77.8%. Whether the species were extinct or radiant, the rate of the second was higher than that of the first time.

Key words: Late Middle Permian, brachiopod, species diversity, evolution, Hechuan area in Chongqing