Late Olenekian assemblages in the western Panthalassa have been recovered from bedded radiolarian chert sequences of an accretionary complex, the Ashio belt. These faunas are documented and considered in terms of radi...Late Olenekian assemblages in the western Panthalassa have been recovered from bedded radiolarian chert sequences of an accretionary complex, the Ashio belt. These faunas are documented and considered in terms of radiolarian diversity and faunal turnover during the latest Permian to Middle Triassic time. The fauna includes 30 radiolarians belonging to Spumellaria or Entactinaria, with two relicts from the Late Permian. This late Olenekian fauna is markedly different from Permian and Anisian faunas, respectively, and is herein named the Minowa fauna. Study of the literature indicates that radiolarian provinces were significantly disconnected between the western Panthalassa and eastern Tethys during late Olenekian time. Furthermore, 121 of 143 species disappeared during late Olenekian time, and in turn 118 new species appeared in the western Panthalassa around the Olenekian Anisian boundary. It is concluded that faunal turnover occurred at least three times between the latest Permian and Middle Triassic. The first turnover is the Paleozoic type radiolarian extinction at the Permian Triassic boundary, the second is the diversification of spheroidal Spumellaria and Entactinaria between early and late Olenekian time, and the third is a faunal turnover from the Minowa fauna to the true Mesozoic type radiolarian faunas that are characterized by multi segmented Nassellaria.展开更多
During the transition from the late Late Permian to the early Early Triassic, faunas over the world were all at a low tide of evolution. But conodonts, as marine fossils, displayed a clear growth series, as compared w...During the transition from the late Late Permian to the early Early Triassic, faunas over the world were all at a low tide of evolution. But conodonts, as marine fossils, displayed a clear growth series, as compared with other groups. This is momentous to explaining the development of organisms in the transition period, and to defining a Permian-展开更多
志留纪最早期的腕足动物群在文献中很少记录,与标准笔石相伴者更为稀罕。江西玉山志留系底部因发现Akidograptus ascensus带的笔石而确定该处盛产志留纪初期(鲁丹早期)、多样性较高的腕足动物群。根据组成、性质与层位,它与浙江江山、...志留纪最早期的腕足动物群在文献中很少记录,与标准笔石相伴者更为稀罕。江西玉山志留系底部因发现Akidograptus ascensus带的笔石而确定该处盛产志留纪初期(鲁丹早期)、多样性较高的腕足动物群。根据组成、性质与层位,它与浙江江山、常山、淳安、余杭等7个地点的同期组合可统一命名为华夏正形贝动物群(Cathay-siorthis Fauna)。它包含了不同群集,都产自细碎屑岩(如泥岩)中,其分布主要受海水深度和距华夏古陆远近的控制。这个动物群生长在奥陶纪大灭绝后的残存期,文章探讨了它的残存特征。研究揭示,奥陶纪末大灭绝对腕足动物演化的一个实质性的贡献在于制约了奥陶纪占优势的A组(正形贝/扭月贝大类群:发育铰合面、窗齿型铰齿、正扭型主突起和简单腕器官)的繁盛态势,滋生了B组(五房贝/无洞贝大类群:发育后转面、弓齿型铰齿和复杂腕器官但缺失正扭型主突起)在志留纪的优势,造成腕足动物宏演化历程中的一次重大转折。文中提出"优势替代滞后型式(Pattern of lag of dominance replacement)",专指A组类群的优势被B组类群替代的时间不是紧跟在奥陶纪末大灭绝之后,而是距大灭绝结束约4Ma之后。文中描记新属华夏正形贝(Cathaysiorthis gen.nov.)。展开更多
文摘Late Olenekian assemblages in the western Panthalassa have been recovered from bedded radiolarian chert sequences of an accretionary complex, the Ashio belt. These faunas are documented and considered in terms of radiolarian diversity and faunal turnover during the latest Permian to Middle Triassic time. The fauna includes 30 radiolarians belonging to Spumellaria or Entactinaria, with two relicts from the Late Permian. This late Olenekian fauna is markedly different from Permian and Anisian faunas, respectively, and is herein named the Minowa fauna. Study of the literature indicates that radiolarian provinces were significantly disconnected between the western Panthalassa and eastern Tethys during late Olenekian time. Furthermore, 121 of 143 species disappeared during late Olenekian time, and in turn 118 new species appeared in the western Panthalassa around the Olenekian Anisian boundary. It is concluded that faunal turnover occurred at least three times between the latest Permian and Middle Triassic. The first turnover is the Paleozoic type radiolarian extinction at the Permian Triassic boundary, the second is the diversification of spheroidal Spumellaria and Entactinaria between early and late Olenekian time, and the third is a faunal turnover from the Minowa fauna to the true Mesozoic type radiolarian faunas that are characterized by multi segmented Nassellaria.
文摘During the transition from the late Late Permian to the early Early Triassic, faunas over the world were all at a low tide of evolution. But conodonts, as marine fossils, displayed a clear growth series, as compared with other groups. This is momentous to explaining the development of organisms in the transition period, and to defining a Permian-
文摘志留纪最早期的腕足动物群在文献中很少记录,与标准笔石相伴者更为稀罕。江西玉山志留系底部因发现Akidograptus ascensus带的笔石而确定该处盛产志留纪初期(鲁丹早期)、多样性较高的腕足动物群。根据组成、性质与层位,它与浙江江山、常山、淳安、余杭等7个地点的同期组合可统一命名为华夏正形贝动物群(Cathay-siorthis Fauna)。它包含了不同群集,都产自细碎屑岩(如泥岩)中,其分布主要受海水深度和距华夏古陆远近的控制。这个动物群生长在奥陶纪大灭绝后的残存期,文章探讨了它的残存特征。研究揭示,奥陶纪末大灭绝对腕足动物演化的一个实质性的贡献在于制约了奥陶纪占优势的A组(正形贝/扭月贝大类群:发育铰合面、窗齿型铰齿、正扭型主突起和简单腕器官)的繁盛态势,滋生了B组(五房贝/无洞贝大类群:发育后转面、弓齿型铰齿和复杂腕器官但缺失正扭型主突起)在志留纪的优势,造成腕足动物宏演化历程中的一次重大转折。文中提出"优势替代滞后型式(Pattern of lag of dominance replacement)",专指A组类群的优势被B组类群替代的时间不是紧跟在奥陶纪末大灭绝之后,而是距大灭绝结束约4Ma之后。文中描记新属华夏正形贝(Cathaysiorthis gen.nov.)。
