Preliminary Study Of Eastern Guizhou Cambrian Crinoids Beginning Of The Ecological And Buried Features

As the oldest class of all known Blastozoan Echinodems, the Eocrinoidea appeared in the early Cambrian and became extinct in the Silurian, and were most diverse during the Cambrian. So far, at least 21 genera of Cambrian eocrinoids are known. .Eocrinoids fossils are particularly numerous in the east of Guizhou, where more than 13000 specimens representing 6 genera were collected and identified by Professor Zhao YuanLong and Ronald Parsley of Tulane University, USA. This work focuses on three genera of eocrinoids from the Kaili Biota and the Balang Biota: Sinoeocrinus lui, Globoeocrinus globulus and Guizhoueocrinus yui,. Fieldwork was conducted at the Wuliu-Zengjiaya section and the Miaobanpo section in JianHe, the Wenglingtang section to the northwest of Kaili, the Jianggu section in Zhenyuan. Study of functional morphology, paleoecology and taphonomy of eocrinoids included collection of fossils, statistical methods, and photography of specimens. Data collected in this study were synthesized with data collected previously by Zhao and Parsley.Eocrinoid fossils in the east of Guizhou often exhibit intact preservation. These specimens all show brachioles, thecae, stalks and attached discs, and a few specimens show anal pyramids. The theca of Globoeocrinus Globulus is spheroidal, with a short stalk and a large attached disc, which is often found affixed to fragments of brachiopod shell or trilobite carapace. The brachioles of this species are long, revolving or even curled. The theca of Sinoeocrinus lui is obpyriform, with a long stalk and an inconspicuous or small attached disc, which may have attached directly to the silty mudstone substrate. The theca of Guizhoueocrinus yui is a prolate ellipsoid. The size of attached disc falls in between the two other species studied. These characteristics show differences among the three species of Eocrinoids. The first characteristic of ontogeny from juvenile stages to adult stages of the three species is an increase in size. Second, the surtural pores are not developed in juvenile stages, but are well-developed in adult individuals. Third, the thecae plates increase both in size and in number. Fourth, the stalks become bigger or thicker. Fifth, the brachioles become longer. Evolutionary trends from Guizhoueocrinus yui in the Early Cambrian to Globoeocrinus Globulus and Sinoeocrinus lui in the Middle Cambrian include an increase in the size of individual thecal plates, a decrease in the number of thecal plates, and an increase in the complexity and number of surtural pores. The characters indicate the diversity of ontogeny and community of eocrinoids and ecology from eastern Guizhou, China. They provide dramatically material for classification of eocrinoids. These are important evidences to understand the Kaili Biota and Balang Fauna were in frequent and rapid depositional events.