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

Abstract

The 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 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. The largest known fragment of O. mirabilis implies that its adult 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.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.

New armoured scalidophorans (Ecdysozoa, Cycloneuralia) from the Cambrian Fortunian Zhangjiagou Lagerstätte, South China

“…), a trunk part of Eopriapulites sphinx from the Zhangjiagou Lagerstätte is about 2.55 mm long (Shao et al . ), the current specimen UMCU 15CHD0819‐009 (Fig. ) is about 3.53 mm long, and UMCU 16CHD0508‐005 (Fig.…”

“…, ; Shao et al . , ; this study), based exclusively on microfossils of Orsten‐type preservation (Maas et al . ).…”

“…They were obtained from the lower part of the second member of the Kuanchuanpu Formation at the Zhangjiagou Lagerstätte (Shao et al . ), Xixiang County, southern Shaanxi Province, South China. The key horizon that yielded the current material has been constrained to be part of the small shelly fossils Anabarites trisulcatus – Protohertzina anabarica Assemblage Zone (Li ; Liu et al .…”

“…; Shao et al . , ), disassociated trunk parts of armoured scalidophorans (Zhang et al . ) and a plausible deuterostome (Han et al .…”

“…; Shao et al . ), the rock samples of phosphatic limestone from the key horizon at the Zhangjiagou Lagerstätte were processed through a routine etching method with diluted acetic acid (10%). Undissolvable residues were dried naturally and then handpicked under a binocular microscope.…”