New macrobenthic cycloneuralians from the Fortunian (lowermost Cambrian) of South China

Abstract

Although morphology-based phylogenetic analyses and molecular data suggested that the cycloneuralians might have emerged in the Ediacaran Period, the oldest known fossil remains of cycloneuralians were first reported from the Cambrian Fortunian Stage of South China, and to date four genera and species as well as nine indeterminate forms have been described. Here, we report the latest discoveries of cycloneuralians from the Fortunian Kuanchuanpu Formation at Zhangjiagou Lagerstätte, Dahe Village, Xixiang County, southern Shaanxi Province, South China. A new genus and species Dahescolex kuanchuanpuensis n. gen. n. sp. is described, and a previously reported genus and species Eopriapulites sphinx is re-described. Dahescolex kuanchuanpuensis n. gen. n. sp. is suggested to be a stem-lineage derivative of Scalidophora, whereas E. sphinx may represent a stem-lineage derivative of Cycloneuralia. From the fragments discovered, the new specimens are suggested to have reached millimeters in dimension, and the original individuals are estimated to have dimensions in centimeter, hence falls within the size range of macrobenthos. Therefore, at least some of the Fortunian cycloneuralians can be considered macrobenthic, and it is suggested here that the Cycloneuralia may have originated in the Fortunian macrobenthos.