An early Cambrian Sidneyia (Arthropoda) resolves the century-long debate of its head organization

We report the extraordinarily preserved euarthropod Sidneyia minor sp. nov. from the Cambrian Stage 3 Xiaoshiba Lagerstätte in Yunnan, South China. So far this is the earliest occurrence of the genus. As with other species of Sidneyia , the new taxon shares similar features such as a crescent-shaped head shield with paired lateral notches for stalked eyes, but more significantly and new, is the presence of three pairs of post-antennal appendages beneath the head shield identified by micro-CT methods. We conclude that Sidneyia is a sister group to other members of Vicissicaudata within the diverse radiation of Artiopoda.