Diversity of cnidarians and cycloneuralians in the Fortunian (early Cambrian) Kuanchuanpu Formation at Zhangjiagou, South China

Abstract

AbstractThe latest discovery of microfossils from the lower Cambrian (Fortunian Stage) Zhangjiagou Lagerstätte in South China are presented. This lagerstätte is rich in exceptionally preserved microfossils, including embryos ofOlivooides multisulcatus,Olivooides mirabilis, andPseudooides prima; hatched stages ofO.multisulcatus,O.mirabilis,Hexaconularia sichuanensis, andQuadrapyrgites quadratacris; and cycloneuralians represented byEopriapulites sphinx. The largest known fragment ofO.mirabilisimplies that its adult length can be more than 9.0 mm with at least 50 annuli, and the longest known specimen ofQ.quadratacrishas at least 18 annuli. These unusually large specimens refute the non-feeding larvae hypothesis forOlivooidesandQuadrapyrgites.Based on the current material, it is inferred that (1) early cnidarians have a high diversity in the Fortunian Stage; (2)P.primamight represent the embryonic stages ofH.sichuanensis; (3) adults ofOlivooidesandQuadrapyrgitesmay have reached centimeter-scale dimensions with more than 50 annuli; (4)OlivooidesandQuadrapyrgitesmay be better interpreted as coronate scyphozoans; (5) cycloneuralians also had a high diversity in the Zhangjiagou Lagerstätte; and (6) cycloneuralians might have originally been part of the early Cambrian meiofauna rather than belonging to the macrobenthos. Such ancestral cycloneuralians might have beenEopriapulites-like, possessing pentaradially symmetric, backward pointing, and internally hollow introvert scalids used as locomotory devices.