Resurgence of cloudinomorph fossils with possible cnidarian affinity at the peak of the Cambrian Explosion (Cambrian Series 2, Stage 3) in southern Shaanxi, China

• DOI: 10.1002/spp2.1596
• Publication Date: 2024-10-02T10:27:06Z
• Authors: Jinzhou Luo; Hong Hua; Meng Gong; Yang Hou; Qiaokun Dai; Song Zhang; Xinzi Wang; Lin Bai

Abstract During the Precambrian–Cambrian transition, tubicolous animals were prevalent among small shelly fossils. These include oldest‐known skeletal fossil Cloudina from terminal Ediacaran, and anabarites hyoliths early Cambrian; considered to be possible annelids, cnidarians, molluscs, respectively. Tubular fossils have important bio‐stratigraphic significance during this period, their diversity evolutionary radiation trend herald Cambrian explosion. However, relative morphological simplicity of these lack preserved soft‐body information has resulted in poor taxonomic constraints. Here, numerous tubular exhibiting multi‐stage cylindrical or conical cups recovered middle–upper Guojiaba Formation Series 2, Stage 3, Mianxian, South China. One new genus ( Mianxiantubus ) three species M. cyathiformis , M . obconicus varius established accommodate affinities remain contentious undetermined been tentatively ascribed Cnidaria. The morphology growth patterns suggest a close relationship with cloudinomorph fossils, although it is notably distinct quintessential cloudinids owing presence transverse septa. Moreover, many other same level, which may extend overlying Xiannvdong (Stage 3), co‐occurring archaeocyathids. This suggests that organisms continued diversify occupied specific ecological niches even peak phase explosion, dominated by bilateral epifaunal vagrants.