The upper part of the Third Member of the Lower Triassic Jialingjiang Formation in western Hubei Province was composed of laminated limestone with 30 meters thickness. It contains many kinds of marine reptile fossils including such as Hupehsuchia, Ichthyosauria and Sauropterygia and others from Yingzishan, Yangping of Yuan’an county to Xunjian, Gujin of Nanzhang county in western Hubei Province. These marine reptiles formed an excellent Nanzhang-Yuan’an fauna characterized by occurrence of abundant Hupehsuchia, which coexisted with Ichthyosauria and Sauropterygia. This fauna indicated that the first radiation of marine reptiles happened and a new ocean ecosystem rebuilt by marine reptiles was formed in the late Early Triassic because its diversities of the Order or genus and species of the marine reptiles were close to that of the Panxian-Luoping fauna which used to be regarded as a typical fauna occurred after biotic recovery in the Middle Triassic.