Early Cambrian Mollusc Watsonella crosbyi:A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2

作     者：LI Guoxiang ZHAO Xin Alexander GUBANOV ZHU Maoyan NA Lin 

作者机构：State Key Laboratory of Palaeobiology and Stratigraphy Nanjing Institute of Geology and Palaeontologythe Chinese Academy of Sciences Nanjing 210008 China CASP Department of Earth Sciences University of Cambridge Cambridge UK 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2011年第85卷第2期

页      面：309-319页

核心收录：

学科分类：0710[理学-生物学] 070903[理学-古生物学与地层学(含：古人类学)] 0709[理学-地质学] 07[理学] 071002[理学-动物学] 

基　　金：supported by the Chinese Academy of Sciences (KZCX3-EW-115) the Ministry of Science and Technology of China (2006FY120300-3) the National Natural Science Foundation of China, and National Science and Technology Major Project (2008ZX05008-001-001) 

主　　题：mollusc Watsonella crosbyi microstructure Terreneuvian Cambrian Stage 2 South China Siberian Platform 

摘      要：The mollusc Watsonella crosbyi was studied on the basis of material from the lower Cambrian Dahai Member of the Zhujiaqing Formation in eastern Yunnan, China and the Pestrotsvet Formation of the Aldan River region in the Siberian Platform. This fossil had been excessively described under different names in the literature, such as Heraultia varensalensis Cobboid, 1935, H. sibirica Missarzhevsky, 1974, Heraultipegma yunnanensis He and Yang, 1982, H. yannanese He and Yang,1982, Watsonella yunnanensis, W. crosbyi Grabau, 1900, etc. Taxonomic revision shows that other species are junior synonyms of W. crosbyi. Analysis of functional morphology implies that W. crosbyi may be rather a heicionelloid than a rostroconch since its univalved conch is untorted endogastric and lacks a rostrum and a true internal pegma. Replicas of the original microstrnctures preserved on the surfaces of phosphatic internal moulds confirm that the shell consists of two layers. The inner layer is lamello-fibrillar, and the outer layer is spherulitic prismatic. The widespread geographical occurrences in both siliciclastic and carbonate rocks of the late Terreneuvian indicate that W. crosbyi is an important index fossil for global correlations and subdivision of the Cambrian Series I （Terreneuvian）.The first appearance datum （FAD） of W. crosbyi is suggested to be a potential GSSP （Global Boundary Stratotype Section and Point） candidate marker for defining the base of the Cambrian Stage 2.