环节动物--早三叠世生物复苏的先驱者？

IS ANNELIDA—PIONEER IN EARLY TRIASSIC BIOTIC RECOVERY?

华南四川广安谢家槽、贵阳花溪和下扬子地区、意大利北部均显示环节动物产生的遗迹化石出现在下三叠统近底部,而节肢动物所产生的遗迹化石出现层位则较高,表明环节动物在二叠纪末生物大灭绝后的复苏早于节肢类造迹生物,也早于其它底栖生物。早三叠世经历了缺乏遗迹化石、环节动物造迹生物所产生的遗迹化石组合以及包括环节动物和节肢类动物的软躯体造迹生物所产生的遗迹化石组合三个阶段。具有较复杂结构的Thalassinoides在加拿大西部早三叠世早期出现,表明高纬度地区海洋生态条件的改善和生物复苏要早于低纬度地区。

The trace fossils made by annelida occur in the lower horizon（Griesbachian）of the Lower Triassic and the trace fossils made by arthropoda occur in the higher horizon of the Lower Triassic in the areas of south China,Lower Yangtze area of China and northern Italy. The trace-maker annelida appeared earlier than trace-maker arthropoda and most benthos in the Early Triassic biotic recovery after the end-Permian mass extinction.From this we can infer that annelida is pioneer of the early Triassic biotic recovery.The evolution of trace fossils and trace-makers experienced three stages：1）lack of trace fossils;2）trace fossils made by annelida;3）trace fossils made by soft-bodied trace-makers mainly consisting of annelida and arthropoda.The fact that the trace fossil Talassinoides with more complex structures in western Canada occur at the lowermost horizon of the Lower Triassic indicates that the biotic recovery after the end-Permian mass extinction in the areas of the north latitude was earlier than that in the equatorial areas.