Chuaria Walcott from the early Cambrian Qingjiang biota: a taxon persisted for billions of years

Abstract

As a globally distributed genus, Chuaria has an extremely long temporal range from the late Paleoproterozoic to the Cambrian Miaolingian but it is still absent in the pre-Miaolingian Cambrian. Here, we describe new specimens of Chuaria from the Qingjiang biota (black shale of the Cambrian Stage 3 Shuijingtuo Formation, ca. 518 Ma) in Hubei Province, South China, and review its tempo-spatial distribution worldwide. Chuaria from the Qingjiang biota is preserved as carbonaceous compressions or impressions that are discoidal or subdiscoidal in outline and range from 1.40 mm to 5.60 mm in diameter, it is interpreted as a spheroidal and thick-walled eukaryote, and its presence fills the early Cambrian gap in the fossil record. Chuaria remained consistent in morphology and survived harsh environmental perturbations throughout its evolutionary history. Its earliest record was restricted in a small region of Columbia supercontinent; thereafter its records were across a range of continents and became worldwide during the time of Rodinia supercontinent.