DataSheet1_A Cambrian fossil from the Chengjiang fauna sharing characteristics with gilled lobopodians, opabiniids and radiodonts.docx

Parvibellus atavus gen. et sp. nov. from the Early Cambrian Chengjiang fauna of China is a small fossil having a distinct cephalic region bearing a pair of lateral projections and a circular, ventral mouth. The trunk bears eleven pairs of probably flap-like appendages and a short pair of terminal projections. This character combination is unique for the Chengjiang biota. A circular ventral mouth is seen in Radiodonta and in some of the gilled lobopodians which are thought to be among the radiodont’s closest relatives. P. atavus, gilled lobopodians, opabiniids, and radiodonts also share the putative character of flap-like appendages along the trunk. However, the new fossil differs from radiodonts and gilled lobopodians by the absence of enlarged and/or raptorial frontal appendages. It also differs from gilled lobopodians by lacking in ventral lobopod limbs and from radiodonts by lacking in stalked eyes. It provisionally resolves as a sister-group to a clade containing the gilled lobopodians, opabiniids, and radiodonts, and could potentially be part of an early radiation of the nektonic lower stem—Euarthropoda.

产自中国早寒武世澄江生物群的新属新种Parvibellus atavus gen. et sp. nov.是一种小型化石，其头部区域特征鲜明，带有一对侧生突起与圆形腹侧口器。躯干具十一对疑似叶状附肢，以及一对短小的末端突起。该特征组合在澄江生物群中具有唯一性。圆形腹侧口器可见于射齿类（Radiodonta）以及部分被认为是射齿类近亲的鳃叶足动物（gilled lobopodians）中。Parvibellus atavus、鳃叶足动物、欧巴宾海蝎类（opabiniids）与射齿类还共享沿躯干分布叶状附肢这一推定特征。然而，该新化石与射齿类和鳃叶足动物的区别在于缺乏膨大或掠食性前附肢；其与鳃叶足动物的另一区别为缺少腹侧叶足肢体，与射齿类的区别则在于无柄眼。该物种经系统发育分析暂被复原为包含鳃叶足动物、欧巴宾海蝎类与射齿类的演化支的姊妹群，或可归入游移型真节肢动物干群（Euarthropoda）基部的早期辐射演化类群。