An atypical Burgess Shale-type fossil assemblage from Cambrian Stage 4 of the Jingshan area, South China: Taphonomy, palaeoecology, and global correlations

摘要

Burgess Shale-type biotas have been widely reported from the Cambrian in North America, Siberia, Greenland, China, and Australia; they are crucial in reconstructing the biotic evolution and ecological interactions of early metazoans. Here, we report an atypical Burgess Shale-type fossil assemblage from the Shilongdong Formation (Cambrian Stage 4) in the Jingshan area, central Hubei Province, South China. The newly recovered fauna is preserved in a nearly two-meter-thick yellowish-green shale unit intercalated within the massive dolomite and dolomitic limestone succession of the upper Shilongdong Formation. The fossil-bearing shale unit is likely deposited in the deep subtidal zone below storm wave base with occasional influence of weak storm flows, which was likely situated in the relatively low location with the interior of the restricted carbonate platform. The presence of the trilobite Redlichia guizhouensis assigns the Jingshan fossil assemblage to the Longwangmiaoan Stage (Cambrian Series 2, Stage 4), which is of similar age to the Jianhe biota, but younger than the Guanshan, Balang, and Shipai biotas, and slightly older than the Kaili biota, South China. The Jingshan assemblage is fossiliferous, containing common shelly and some soft-bodied fossils. It comprises algae, brachiopods, arthropods, hyoliths, priapulid worms, echinoderms, possible cnidarians, molluscs, and some enigmatic organisms. The fossils retain soft parts, including brachiopods with pedicles and delicate setae, a naraoiid with the antenna preserved and digestive tracts. The diversity of the assemblage is limited compared with better-known biotas of similar age, but investigation is at a preliminary stage. It is an important geographical extension of the Burgess Shale-type biotas in China and provides more information about the Cambrian Explosion of life and biodiversity by comparing fossiliferous horizons in a chronological framework.