Chuandianella ovata: An early Cambrian stem euarthropod with feather-like appendages

Abstract

Micro-CT scanning reveals unprecedented three-dimensional soft anatomy of the early Cambrian (Epoch 2, Age 3) euarthropod Chuandianella ovata. We interpret the presence of an elongate, antenniform first appendage, and a short uniramous second appendage, followed by 10 homonomous biramous appendages comprising a short paddle-shaped exopod and a unique feather-like limb-branch with at least 27 podomeres each of which bears a long blade-like endite with a short terminal seta: we interpret this as the endopod. Alternative interpretations, that these limbs might represent an epipod+basipod or epipod+exopod arrangement, are unlikely, in that they would require either the complete reduction of the exopod or the endopod. We also find no evidence for head appendage morphologies that would support a more crownward position, for example among pancrustaceans, that has previously been suggested for