New Discovery of Small Shelly Fossils from the Early Cambrian Xinji Formation in Western Henan Province, North China

The Cambrian successions in North China (NC) have long been a focus of paleontological and stratigraphical interest. The phosphorus-bearing Xinji Formation is a particular hot spot as it represents the earliest Cambrian sediments in many regions of the NC, playing key roles in deciphering the early radiation of biomineralized animals. However, biomineralized animal fossils of the Xinji Formation in western Henan Province remain poorly understood, hampering a comprehensive understanding of the biostratigraphic and evolutionary significance of the Xinji assemblage. Here we report abundant small shelly fossils (SSFs) from the basal phosphatic limestone of the Xinji Formation in western Henan Province.Preliminary taxonomic identification revealed a high-diversity fauna characterized by exceptionally preserved Hyoliths, Helcionelloids, Gastropods, Lingulates, Bivalves, Chancelloriids, Poriferans, Arthropods, Echinoderms, Cnidarians, and various skeletal remains of uncertain taxonomic affinity. Biostratigraphically important taxa include Stenotheca, Pelagiella, Triplicatella, and Anabarites, indicating Cambrian Stage 3 to Stage 4 for the Xinji Formation in western Henan Province. By comparing the taxonomic similarity of the Xiji Formation with adjacent tectonic units during the early Cambrian, the Xinji fauna provides critical evidences for constraining the palaeogeographic position of the NC.Therefore, this study adds to a better understanding on the biodiversity of the Xinji Formation with implications on its depositional age and paleogeographic setting of the NC.