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

Although molecular studies estimated that cycloneuralians might have originated in the Ediacaran Period and diversified in the early Cambrian, it was not until 2014 that they were first reported from the Cambrian Fortunian Stage. To date only two species and five indeterminate forms have been described. Here, we report new three-dimensionally phosphatized microfossils of cycloneuralians from the Fortunian Zhangjiagou Lagerstatte, South China. Two new genera and species, Qinscolex spinosus gen. et sp. nov. and Shanscolex decorus gen. et sp. nov., and Indeterminate Forms 1-7 are described and tentatively assigned to total-group Scalidophora, greatly increasing the diversity of the Fortunian cycloneuralians. These Fortunian cycloneuralians have diverse cuticular spines, plates, and spinose sclerites of various sizes on the trunk, thus assignment of co-occurring fragmented trunk parts or disassociated spines or sclerites to a specific species is currently impossible. Some of the Fortunian cycloneuralians might have reached a centimetre in length; they may have been temporary meiobenthos in their juvenile or younger adult stages, only joining the macrobenthos when they reached macroscopic dimensions. It is proposed that an introvert with hexaradially symmetric and internally hollow scalids might be the plesiomorphic state for cycloneuralians.