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Abstract: South China with its rich fossil record is an important region for studying Early Cambrian metazoan diversity patterns. Compilation of a database of metazoan genera from the traditional Lower Cambrian (Cambrian Series 1–2) of South China allows a quantitative analysis of biodiversity changes. The dataset shows that about 876 genus names have been reported from the Lower Cambrian of South China. Of these only about 582 genera are now considered valid after taxonomic scrutiny. Plotting generic diversity shows a two-part, first-order trend: 1, diversity increase through the most of the Meishucunian and Qiongzhusian stages (South China usage), but punctuated by a modest decline during the upper Meishucunian; followed by 2, diversity decline in the Canglangpuan and Longwangmiaoan stages (South China usage). About 155 genera of small shelly fossils (SSFs) occur in Meishucunian rocks. The Meishucunian fauna is dominated by helcionellids, orthothecimorph hyoliths and other enigmatic fossils and is very consistent with the pretrilobitic ‘Tommotian Fauna’. Diversity increases in the Qiongzhusian stage, reaching 304 genera, the peak value known for the Cambrian. The Qiongzhusian fauna is characterized mainly by the occurrence of dominant pan-arthropods and crown-group brachiopods, representing an initial phase of the Cambrian Evolutionary Fauna. A substantial decline in generic diversity through the Canglangpuan (ca 153 genera) and Longwangmiaoan (ca 69 genera) stages is due partly to a eustatic regression, and it approximates the global pattern, reflecting an extinction event at the end of the Lower Cambrian. The observed regional biodiversity through this interval has both evolutionary and taphonomic influences: the decline in SSF diversity beginning in the upper Meishucunian was not only related to the decimation of SSFs, but also to a reduction in phosphogenesis. An apparent peak in diversity during the Qiongzhusian was somewhat exaggerated by the exceptional Chengjiang Biota. [Copyright &y& Elsevier]

Abstract: Small shelly fossils (SSFs) occur widely on the Yangtze Platform and have great potential for biostratigraphic subdivision of pre-trilobitic Early Cambrian strata. Based on the SSF record of the shallow water realm, five biozones can be recognized for the Meishucunian Stage. In ascending order the biozones are: Anabarites trisulcatus–Protohertzina anabarica Assemblage Zone; Paragloborilus subglobosus–Purella squamulosa Assemblage Zone; Watsonella crosbyi Assemblage Zone (formerly Heraultipegma yunnanensis Zone); poorly fossiliferous interzone; Sinosachites flabelliformis–Tannuolina zhangwentangi Assemblage Zone. In addition one SSF biozone is recognized for the overlying Qiongzhusian Stage: Pelagiella subangulata Taxon-range Zone. The formerly used Siphogonuchites triangularis–Paragloborilus subglobosus Zone and Heraultipegma yunnanensis Zone are discussed and redefined. Approximately 80 species of SSFs were screened for their spatial and temporal distribution on the Yangtze Platform. Variations in lithofacies and biofacies can be recognized throughout the Yangtze Platform, extending over an area of 2000×900 km. In a deeper water shelf setting the first zone is represented by the Protohertzina anabarica–Kaiyangites novilis Assemblage Zone, while younger zones are not recognized in the southern region. At the northern platform margin the Qiongzhusian is represented by the Ninella tarimensis–Cambroclavus fangxianensis Assemblage Zone and the Rhombocorniculum cancellatum Taxon-range Zone. The southeastern Shaanxi–western Hubei region followed a slightly different lithological and faunal development than the rest of Yangtze Platform, indicating a stronger similarity with parts of East Gondwana. Some taxa such as W. crosbyi, P. subangulata, R. cancellatum, Microdictyon effusum, A. trisulcatus, Protohertzina unguliformis, and P. anabarica occur nearly worldwide and support an international correlation of Early Cambrian sequences between the Yangtze Platform and smaller West Gondwanan blocks, Siberia, Newfoundland, and Australia. The six investigated zones of the Yangtze Platform comprise an interval spanning the early Nemakit–Daldynian to the late Atdabanian/early Botoman Stage on the Siberian Platform. Palaeobiogeographic analysis revealed a strong taxic similarity between the Yangtze Platform and the Tarim Platform. A smaller number of species are shared with other West Gondwanan platform fragments such as India and Iran. Palaeobiogeographic results do not support the previously reported position of the South China Block between Australia and Siberia during the Early Cambrian. [Copyright &y& Elsevier]

The lower Cambrian (Stage 3) Yu'anshan Formation in Yunnan Province, South China hosts the Chengjiang Lagerstätte , an exceptional window on the Cambrian Explosion. However, skeletal microfossils from this formation have long been neglected owing to the dominance of siliciclastics over carbonates. Here we characterize a new assemblage of small shelly fossils from the Maotianshan Shale Member of the Yu'anshan Formation. The assemblage consists of univalved mollusc, hyolith and brachiopod shells, trilobite and bradoriid carapaces, chancelloriid sclerites, sponge spicules, and echinoderm ossicles. Combining this information with taxonomic data previously tabulated for fossil assemblages from three other facies, we performed quantitative comparisons of the genus-level taxonomic diversity and modes of life and nutrition of four mutually equivalent, early Cambrian (Age 3) paleocommunities: (1) skeletal faunas of the inner shelf; (2) predominantly soft-bodied faunas of the intra-shelf basin; (3) archaeocyathan faunas of the carbonate shelf; and (4) sponge-dominated faunas of the slope to basin areas. The taxonomic and paleoecological distinctness of these four paleocommunities indicate possible low levels of competition within the communities and rapid expansion of habitat (ecospace) ranges, though with similarities in the taxonomic composition of poriferans and arthropods reflecting the rapid migration of these two groups into new habitats. The present, integrative study provides a more comprehensive portrait of metazoan diversification and paleocommunity evolution during the peak phase of the Cambrian Explosion than do investigations based on single communities. • New assemblage of skeletal fossils from the Cambrian Stage 3, South China. • The fauna is dominated by hyoliths, chancelloriids, bradoriids and molluscs. • The different paleocommunity compositions and structures are documented. • The paleocommunitites are highly facies-controlled. • The highest biodiversity of the Cambrian Explosion in South China [ABSTRACT FROM AUTHOR]