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

The latest discovery of microfossils from lower Cambrian (Fortunian Stage) Zhangjiagou Lagerstätte in South China are presented. This lagerstätte is rich in exceptionally preserved microfossils, including embryos of Olivooides multisulcatus, Olivooides mirabilis, and Pseudooides prima, hatched stages of O. multisulcatus, O. mirabilis, Hexaconularia sichuanensis and Quadrapyrgites quadratacris, and cycloneuralians represented by Eopriapulites sphinx and a new form. The largest known fragment of O. mirabilis implies that its adults length can be more than 9.0 mm with at least 50 annuli, and the longest known specimen of Q. quadratacris has at least 18 annuli. These unusually large specimens refute the non-feeding larvae hypothesis for Olivooides and Quadrapyrgites. New material documented here includes two new types of fossil embryos, one with hexaradial symmetry and the other with octaradial symmetry, as well as a new cycloneuralian with two tail spines. Based on the current material, it is inferred that 1) early cnidarians have a high diversity in the Fortunian Stage; 2) P. prima might represent the embryonic stages of H. sichuanensis; 3) adults of Olivooides and Quadrapyrgites may have reached centimeter scale dimensions with more than 50 annuli; 4) Olivooides and Quadrapyrgites may 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 been Eopriapulites-like, possessing pentaradially symmetric, backward pointing, and internally hollow introvert scalids used as locomotory devices