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.

本研究报道了产自华南下寒武统幸运阶（Fortunian Stage）张家沟特异埋藏化石库（Zhangjiagou Lagerstätte）的最新微体化石（microfossils）发现。该化石库保存有大量特异埋藏的微体化石，包括多槽橄榄形虫（Olivooides multisulcatus）、奇异橄榄形虫（Olivooides mirabilis）与原始假拟虫（Pseudooides prima）的胚胎化石，多槽橄榄形虫、奇异橄榄形虫、四川六锥虫（Hexaconularia sichuanensis）与方形四锥虫（Quadrapyrgites quadratacris）的孵化阶段标本，以及以棘形始古吻虫（Eopriapulites sphinx）与一新类群为代表的环神经动物（cycloneuralians）化石。已知最大的奇异橄榄形虫标本片段表明，其成体体长可超过9.0毫米，至少具有50个体环；而已知最长的方形四锥虫标本至少具有18个体环。这类异常大型的标本驳斥了橄榄形虫属与四锥虫属为非摄食幼虫的假说。本次研究报道的新材料包含两类全新的化石胚胎：一类具有六辐射对称结构，另一类具有八辐射对称结构，同时还发现了一具带有两枚尾刺的全新环神经动物化石。基于本次研究的标本材料，可得出以下六点推论：1）幸运阶的刺胞动物（cnidarians）早期类群具有较高的多样性；2）原始假拟虫可能代表四川六锥虫的胚胎发育阶段；3）橄榄形虫属与四锥虫属的成体体长或可达厘米级，且体环数量超过50；4）橄榄形虫属与四锥虫属更适宜被归类为冠群钵水母（coronate scyphozoans）；5）张家沟特异埋藏化石库中的环神经动物类群同样具有较高多样性；6）环神经动物最初可能属于寒武纪早期小型底栖动物（meiofauna）类群，而非大型底栖生物（macrobenthos）。这类原始的环神经动物可能类似始古吻虫属（Eopriapulites）类群，具有五辐射对称、向后指向且内部中空的翻吻棘（introvert scalids）作为运动器官。