Fish Fossils And Their Paleoecological Features Of Luoping Biota, Middle Triassic, Yunan, South China

The palaeogeographic location of Luoping area in Middle Triassic period located between the east of Kangdian old land and the western edge of Nanpanjiang basin. In the period of Middle Triassic, there was a series of small sags within the platform distributed on the Yangtze carbonate platform under the function of Indo-China Orogeny. Luoping area was one of the sag within the platform.Luoping Biota was preserved in the laminated micritic limestone, which belong to the second member of Guanling Formation, Middle Trassic. Various fossils have been found in Luoping Biota including marine vertebrates, arthorpods, echinoderms, mollusk, continental plants as well as some undetermined species. And its species diversity is much more than the Guanling Fauna, Xingyi Fauna and Panxian Fauna in Southern China. Among the vertebrate fossils, fish fossils are the main part. As a result, studing on the fish fossils is of great significance to the research of the whole biota. Luoping Biota has a great variety of fish fossils. There are Palaeonisciformes, Saurichthyiformes, Perleidiformes, Peltopleuriformes, Semionotiformes, Coelacanth- iformes and some non-semionotiformes neopterygians. This thesis describes those different types respectively. Some of them is new genus and species, for example, Luoxiongichthys hyperdorsalis gen. et sp. nov. and Luopingcoelacanthus eurylacrima- lis gen. et sp. nov.In order to reflect the proportion of the three typical types of fish fossils, we do the statistic analysis and draw the histogram on the basis of those fish fossils from Shangshikan Section. It is proved that the neopterygian take a great proportion in the total number. That is to say, neopterygian began to radiate in the Middle Triassic.The taphonomic features of fish fossils is studied based on the 31th. layer of Shangshikan Section. It is proved that they all preserved at the orignal places. Most of well-preserved fish fossils correspond to grey-black laminated micrite and muddy limestone. It indicates undisturbed and anoxic bottom environment.Different fossils play different roles in Luoping Biota. From the primary producer, primary customer, senior customer to decomposer, Luoping Biota has a healthy food chain. On the basis of assistant sections (Machang Section, Luoke Section, Xiaozhai Section, Sifangshi Section, Jindai Section and Menqianpo Section) and fossil outcrop, we recover the paleoenvironment of Luoping Biota. Firstly, we determine the key area which has the fossil layers on the basis of the fossil outcrop. Secondly, we observe the outarea from the key area and find the scope of Luoping sag within the platform. The western boundary is along the Ameizhe-Chaan-Leniduo village. Beyond the western bountary is the Luxi sag within platform. The eastern boundary is along Tudimiao-Bengshan village. The eastern Badahe is turbidity deposite, making the transition from platform to Nanpanjiang Basin. The Luoping sag within platform provides a fantastic home for marine lives.