中文摘要：

在对宜昌陈家河大湾组，（Arenig期）腕足动物化石进行逐层统计和详细研究的基础上，以笔石带为单位讨论腕足动物分类单元多样性的变化，发现该地区腕足动物属级分异度在Corymbograptellus deflexus带达到首次峰值，比上扬子区处于正常浅海底域地区（如贵州桐梓、沿河一带）的腕足动物宏演化趋势（在Didymograptellus eobifidus带达到首次峰值）晚了一个笔石带的时限，辐射主要缘于Sinorthis群落在本地区的出现和极度繁盛。华南早、中奥陶世腕足动物的辐射中心在相对近岸的上扬子区（特别是处于正常浅海底域的贵州桐梓一带）。

英文摘要：

Based on systematic and statistical study on the brachiopods from the Dawan Formation at Chenjiahe, Yiehang, western Hubei Province, the biodiversity change is discussed in terms of the graptolitie biozones. The Early to Mid Ordovieian braehiopod radiation in the study area got its first aeme at generic level at the beginning of the Corymbograptus deflexus Biozone, which was nearly one biozone later than the maeroevolutionary trend of braehiopods on the Upper Yangtze Platform. The radiation was again owing to the occurrence and flourish of the Sinorthis Community. The Sinorthis Community first appeared in the normal marine shallow water benthic regimes （lower BA2 to BA3）, such as in the Tongzi area, and the Early to Mid Ordovician brachiopod radiation centre was at those comparatively near shore localities, away from Yichang （centre of the Yangtze Platform, far away from the paleoshoreline） for a certain amount of distance.