Data from: Cambrian petalonamid Stromatoveris phylogenetically links Ediacaran biota to later animals

Macro-organisms of the Ediacaran period (635-541 Ma) were large and morphologically complex, with some living in aphotic habitats, presenting the possibility that they were early animals. However, ‘bizarre’ Ediacaran morphologies and mouldic preservation have frustrated comparison to later taxa. Consequently, both the positions of Ediacaran biota in the tree of life and the origins of the Metazoa have been unresolved. Here we provide phylogenetic evidence to identify Ediacaran macro-biota as animals, based on 206 new fossils of Stromatoveris psygmoglena from the Lower Cambrian Chengjiang Lagerstätte. Exceptionally preserved soft-tissue anatomy shows that Stromatoveris was a soft-bodied, radially symmetric animal with multiple, sub-branched petaloids and a differentiated holdfast. Photo-referenced morphological character analysis enables phylogenetic reconstruction of a monophyletic clade designated Petalonamae, following Pflug, 1970, that unites Stromatoveris with iconic Ediacaran genera (Rangea, Pteridinium, Ernietta, Swartpuntia, Arborea, Pambikalbae and Dickinsonia), placed as sister-group to the Eumetazoa. Therefore the Ediacaran petalonamids are established as animals, based on phylogenetic bracketing within the Metazoa. From these findings, it follows that petalonamids remained an important component of Cambrian marine ecosystems and that the metazoan radiation can be dated to a minimum age of between 558 and 571 Ma.

埃迪卡拉纪（Ediacaran Period，635~541百万年前）的宏体生物体型硕大且形态复杂，部分类群栖息于无光生境，提示其可能为早期动物。然而，埃迪卡拉纪生物怪异的形态特征与铸型保存方式，阻碍了其与后世分类群的比对研究。因此，埃迪卡拉纪生物群在生命之树中的演化位置，以及后生动物（Metazoa）的起源问题长期悬而未决。本研究基于采自下寒武统澄江特异埋藏化石库（Chengjiang Lagerstätte）的206枚新发现的斯氏帚形虫（Stromatoveris psygmoglena）化石，提供了系统发育证据，将埃迪卡拉纪宏体生物归属于动物界。该化石的软组织解剖结构保存异常精美，显示斯氏帚形虫为一类软体、辐射对称动物，具有多组亚分枝瓣状结构与分化明显的固着器。本研究采用影像参照的形态性状分析方法完成了系统发育重建，确立了单系演化支扇盘动物类（Petalonamae，遵循Pflug 1970年的命名规则），该演化支将斯氏帚形虫与典型埃迪卡拉纪属类（Rangea、Pteridinium、Ernietta、Swartpuntia、Arborea、Pambikalbae以及Dickinsonia）归入同一类群，并将其置于真后生动物（Eumetazoa）的姊妹群位置。因此，基于后生动物类群内的系统发育括号法，扇盘动物类被确立为动物类群。据此研究结果可知，扇盘动物类在寒武纪海洋生态系统中仍占据重要地位，同时后生动物辐射演化的最小年代可追溯至558~571百万年前。