A Cambrian unarmoured lobopodian, †Lenisambulatrix humboldti gen. et sp. nov., compared with new material of †Diania cactiformis.

Cambrian marine lobopodians are generally considered as predecessors of modern panarthropods (onychophorans, tardigrades, and arthropods). Hence, further study of their morphological diversity and early radiation may enhance our understanding of the ground pattern and evolutionary history of panarthropods. Here, we report a rare lobopodian species, †Lenisambulatrix humboldti gen. et sp. nov. ("Humboldt lobopodian"), from the early Cambrian Chengjiang Lagerstätte and describe new morphological features of †Diania cactiformis, a coeval armoured lobopodian nicknamed "walking cactus". Both lobopodian species were similar in possessing rather thick, elongate lobopods without terminal claws. However, in contrast to †Diania cactiformis, the body of which was heavily armored with spines, the trunk and limbs of the Humboldt lobopodian were entirely unarmored. Our study augments the morphological diversity of Cambrian lobopodians and presents two evolutionary extremes of cuticular ornamentation: one represented by the Humboldt lobopodian, which was most likely entirely "naked", the other epitomized by †D. cactiformis, which was highly "armoured".