皖南地区震旦系古介形类化石的发现及其意义

Discovery of the Sinian Ostracod fossils in south Anhui and the implications

皖南地区下震旦统蓝田组(相当于陡山沱阶)下部植物宏体藻层内发现古介形类化石是一个重大发现。它是已知古介形类产出的最低层位,将原初见于早寒武世地层梅树村阶底部下延至早震旦世地层陡山沱阶下部(时限前溯约130Ma)。文中根据古介形类化石的结构、构造、壳质及软体等特征,将其归于动物分类系统的Arthropoda—Crustacea—Ostracoida—Archaeostaidae—Sinogella(gen.nov.)—S.lantianensis(gen.et sp.nov.);并作为讨论Sinogella种族发生演化史的依据,认为在自然选择支配下古介形类历经具节肢—外套膜—几丁质外壳的重要发展阶段,其中尤以外套膜的出现最为重要,其功能是保护介虫躯干,继后,外套膜分泌几丁质外壳,形成新属种Sinogella lantianensis(gen.et sp.nov.)等。这些化石的发现为原称"蓝田植物群"更名为"蓝田生物群"提供了确凿的动物化石证据。

It is a big find that Ostracod was discovered in the lower flora macro body algae of the lower Sinian Lantian Formation （equiv. Doushantuo Stage） in south Anhui. This is the lowest horizon where Ostracods have been discovered so far, i.e., the lower Doushantuo Stage of early Sinian, about 130Ma earlier than the bottom of Meishucun Stage of early Cambrian in which they were found before. According to the features of the texture, structure, shell and soft body of the fossils, these Ostracods are classified into the Arthropoda---Crustacea-＇-OstracoidauArchaeostaidae--Sinogella （gen.nov.）--S.lantianensis（gen.etsp.nov.）. They serve as a basis to discuss the history of generation and evolution of Sin- ogella races. It is suggested that under natural selection Ostracods have experienced such major development stages as having segmental appendage to mantle to chitin shell, of which the most important is mantle coming into being that pro- tects the mmk of Ostracod, and then secretes chitin shell to form new species Sinogellalantianensis（gen.etsp.nov.）, etc. The discovery of these fossils provides solid evidence for changing the former ＂Lantian flora＂ to ＂Lantian biota＂ .