The Study Of Micro-Brachiopods From The Tsinghsutung Formation Of Cambrian At Songtao,Guizhou

The Tsinghsutung Formation of Cambrian is exposed in Panxin,Songtao County,Guizhou Province,representing the deposit formed in Yangtze platform.We study the Micro-brachiopods by combined the field exploration and laboratory experiments.A large number of Micro-brachiopods fossils were collected in the Tsinghsutung Formation of Cambrian at Songtao County,Guizhou Province by acetic acid.They are Palaeobolus liantuoensis?Lingulella sp.?Eoobolus cf.triparilis?Kyrshabaktella davidii?Schizopholis napuru?Eothele sp.?Eohadrotreta zhenbaensis?E.sp.and Hadrotreta cf.djagoran,including 8 genera 4 species 2 conformis and 3 undetermined species by research.E.zhenbaensis and P.liantuoensis are very common species.There are first discovered in the Tsinghsutung Formation of Cambrian at Songtao County,Guizhou Province.The micro-structure of brachiopod fossils in the Tsinghsutung Formation of Cambrian at Songtao County,Guizhou Province by Scanning electron microscope(SEM).On the exterior of morphological,there are lots of hemispherical pits on the post larval outer surface of dorsal valve,and circular holes on the mature shell of E.zhenbaensis.also have lots of points and fold on the surface at mature shell of dorsal valve of Schizopholis napuru and Eothele sp.On the interior,has cardinal muscle scars on the dorsal valve or ventral valve interior of E.zhenbaensis.Polygonal structures are visible above the cardinal muscle scar.And this structure were distributed at the apical process,vascular lateralia of ventral valve,and median buttress,median ridge of dorsal valve.Lamellar,short columnar and baculate microstructures were found in the apical process of the ventral valve of E.zhenbaensis by shell structures research.A round hole with 0.5 ?m diameter appears on the short columnar microstructure.It is would be needed to discussion further which provided channels for the secretion of minerals in the shell because of the limited number of specimens.The microscopic analysis of shell morphology and microstructure of brachiopods play a significant role in understanding brachiopods ecology and systematic classification,and it also provides new materials for enriching the fossil composition of brachiopods in Tsinghsutung Formation.By comparing with these reported features of E.zhenbaensis,it is found that the new specimens demonstrate more similar internal structures to E.zhenbaensis of southern Shaanxi,and western Hubei,but differ from that of Majiang in the deep transition slope facies.By comparing the ratio of length to width and Growing features of median ridge of dorsal valve of E.zhenbaensis in different areas,it is possibly suggests that the water depth influences the dorsal internal structure of E.zhenbaensis.Meanwhile,the length-width ratio of dorsal valve of E.zhenbaensis reduces and median ridge of dorsal valve of E.zhenbaensis Elongate with increasing water depth,which provides evidence for further discussing how the internal structural of E.zhenbaensis are influenced by water depth.In short,the discovery of the E.zhenbaensis in the Tsinghsutung Formation of Cambrian Series 2,at Panxin section,Songtao County,Guizhou Province,not only provides new materials for studying the morphological and structural characteristics,but also enriches the brachiopods composition of the Tsinghsutung Formation.