A Fossil Assemblage from the Lower Cambrian Liuchapo Formation in Guizhou Province and Its Implications for Biostratigraphy and Evolution

The Ediacaran–Cambrian transition (ECT) was characterized by substantial alterations in the Earth-life system and represented a crucial juncture in the evolution of complex multicellular organisms. South China provides indispensable fossil and stratigraphic data for carrying out relevant research. Nevertheless, previous studies have predominantly concentrated on the fossil-abundant shallow-water platform facies, resulting in an inadequate comprehension of the biosphere in deep-water regions. This research conducts a comprehensive investigation of a fossil assemblage from the chert-dominated Liuchapo Formation at the Jiaobang section in Jianhe County, Guizhou Province. The Liuchapo Formation signifies a slope depositional environment. By means of acid etching and thin-section observations, a substantial quantity of fossils has been identified. These fossils encompass sponge spicules, hyoliths, possible protoconodonts (? Protohertzina sp.) and zhijinitids (? Zhijinites sp.), spherical acritarchs, Megathrix longus, and diverse types of multicellular algae, along with the enigmatic Poratusiramus sp., globular fossils, and morphologically varied filamentous and sheet-like fossils. This fossil assemblage belongs to the Cambrian Fortunian Stage, and the skeletal remains are mainly constituted by sponge spicules. This fossil assemblage encompasses taxa that are common to shallow-water environments as well as taxa that are exclusive to deep-water settings, which holds significance for potential stratigraphic correlation and evolutionary investigations. These findings supplement the palaeontological data from the Fortunian slope facies, and the abundance of fossils in the deep-water facies of the ECT far surpasses traditional conceptions and calls for further exploration and in-depth research.