Data from: Ontogeny, morphology and taxonomy of the soft-bodied Cambrian ‘mollusc’ Wiwaxia

The soft-bodied Cambrian organism Wiwaxia poses a taxonomic conundrum. Its imbricated dorsal scleritome suggests a relationship with the polychaete annelid worms, whereas its mouthparts and naked ventral surface invite comparison with the molluscan radula and foot. 476 new and existing specimens from the 505-Myr-old Burgess Shale cast fresh light on Wiwaxia's sclerites and scleritome. My observations illuminate the diversity within the genus and demonstrate that Wiwaxia did not undergo discrete moult stages; rather, its scleritome developed gradually, with piecewise addition and replacement of individually secreted sclerites. I recognize a digestive tract and creeping foot in Wiwaxia, solidifying its relationship with the contemporary Odontogriphus. Similarities between the scleritomes of Wiwaxia, halkieriids, Polyplacophora and Aplacophora hint that the taxa are related. A molluscan affinity is robustly established, and Wiwaxia provides a good fossil proxy for the ancestral aculiferan – and perhaps molluscan – body plan.软躯体寒武纪生物威瓦亚虫（Wiwaxia）长期以来是分类学上的难解谜题。其覆瓦状排列的背部骨片复合体（scleritome）暗示其与多毛类环节动物存在亲缘关系，而它的口器与裸露的腹面则让人联想到软体动物的齿舌与腹足。 本次研究依托5.05亿年前布尔吉斯页岩（Burgess Shale）中出土的476件新标本及现存馆藏标本，为威瓦亚虫的骨片与骨片复合体研究提供了全新视角。本研究的观察结果揭示了该属内的形态多样性，并证实威瓦亚虫并未经历离散的蜕皮阶段；相反，其骨片复合体呈渐进式发育，通过逐段添加与替换单个分泌形成的骨片完成生长。 研究中识别出威瓦亚虫体内存在消化道与匍匐足，进一步巩固了它与同期生物齿形虫（Odontogriphus）的亲缘关系。威瓦亚虫、霍克壳类（halkieriids）、多板纲（Polyplacophora）与无板纲（Aplacophora）的骨片复合体之间存在诸多相似特征，这暗示这些类群之间存在亲缘关联。 本研究有力证实了威瓦亚虫的软体动物亲缘属性，它可作为原始铠壳类（aculiferan）——乃至原始软体动物——躯体构型的优质化石替代模型。