Palaeontology and biostratigraphy of the Early Cambrian Meishucunian Stage in Yunnan Province, South China

Abstract

The skeletal fossils of the Early Cambrian Meishucunian Stage from two key localities (Meishucun, Jinning County, and Xianfeng, Xundian County) in eastern Yunnan Province, China, are described and illustrated in detail to provide a basis for improved palaeobiological and biostratigraphical work. About 1250 new SEM illustrations (including a large number of stereo-pairs) of well-preserved material are presented. The taxonomy is extensively revised. When biological and preservational variability are taken into account, the number of genera and species may be reduced through synonymy to about one third of that reported in the literature. Thirty-eight genera (2 of which are new) and 57 species (5 of which are new) are described. The biology and affinities of many of these taxa are also diseussed, but excursions into suprageneric taxonomy are generally restrained. The Meishucunian biotas of Yunnan consist of three successive assemblages with very few taxa in common. The first, the Anabarites-Protohertzina-Arthrochites Assemblage, is dominated by Anabarites and other sedentary tube-dwelling organisms, but non-sedentary benthic mollusc-like fossils (Canopoconus) and probable predators (Protohertzina) also occur. The key elements of this fauna have a wide geographical distribution and may be compared with the earliest skeietal faunas on the Siberian Platform, the Canadian Cordillera, and other regions. The second, the Siphogonuchites-Paragloborilus Assemblage, is characterized by a great diversity of vagile mollusc-like and multisclerite-bearing animals, but also sedentary tube-dwellers and some possible predators (Cyrtochitesand Yunnanodus) occur. This fauna is largely endemic. The third, the Lapworthella-Tannuolina-Sinosachites Assemblage, is mainly characterized by widely distributed taxa of multisclerite-bearing animals (chancelloriids, Halkieria, Tannuolina, and Lapworthella). It has elements in common with late Atdabanian faunas in other regions of the world.