Yang Xiaoyu, Aguado M Teresa, Helm Conrad, Zhang Zhiqian, Bleidorn Christoph
Yunnan Key Laboratory for Palaeobiology, Institute of Palaeontology, Yunnan University, Kunming 650500, People's Republic of China.
Animal Evolution and Biodiversity, Georg-August-Universität Göttingen, Göttingen 37073, Germany.
R Soc Open Sci. 2024 Apr 10;11(4):231580. doi: 10.1098/rsos.231580. eCollection 2024 Apr.
Molecular clock estimates suggest the origin of Annelida dates back to the Ediacaran period, which is in discordance with the first appearance of this taxon in the early Cambrian, as evidenced by the fossil records of stem-group and basally branching crown-group annelids. Using new material from the early Cambrian Guanshan biota (Cambrian Series 2, Stage 4), we re-interpret Zhao, Li & Selden, 2023, as the earliest known errantian annelid. has a prominent anterior end bearing three pairs of putatively sensory appendages and a pair of anterior eyes; a muscular eversible pharynx with papillae is identified. The presence of enlarged parapodia with acicula-like structures and long capillary chaetae suggests a pelagic lifestyle for this taxon. Our phylogenetic analyses recover within the Phyllodocida (Pleistoannelida, Errantia), extending the origin of Errantia back to the early Cambrian. Our data are in line with the hypothesis that Annelida diverged before the Cambrian and indicate both morphological and ecological diversification of annelids in the early Cambrian.
分子钟估计表明，环节动物门的起源可追溯到埃迪卡拉纪，这与该分类单元在寒武纪早期的首次出现不一致，干群和基部分支冠群环节动物的化石记录证明了这一点。利用寒武纪第二统第4阶早期关山生物群的新材料，我们重新将赵、李和塞尔登（2023年）鉴定的物种解释为已知最早的游走类环节动物。它有一个突出的前端，有三对可能是感觉附肢和一对复眼；确定有一个带乳头的可外翻肌肉咽。具有针状结构的扩大的疣足和长的毛细管刚毛的存在表明该分类单元的浮游生活方式。我们的系统发育分析将该物种置于叶须虫目（多毛纲，游走亚纲）之内，将游走亚纲的起源追溯到寒武纪早期。我们的数据符合环节动物门在寒武纪之前分化的假说，并表明寒武纪早期环节动物在形态和生态上的多样化。
