Lobopodians are an iconic group of animals from the Paleozoic that includes Hallucigenia and Opabinia, as well as living animals such as tardigrades and velvet worms. They would also eventually give rise to the first arthropods by developing a hard, sclerotized exoskeleton. During the Cambrian, a rare subset of lobopodians possessed large swimming flaps, sometimes alongside ventral walking limbs. A new, large-bodied pelagic lobopodian from the Cambrian of Nevada is described, possessing more swimming flaps than any other lobopodian or radiodont.

Lobopodians are an iconic and diverse group of animals from the Cambrian, which alongside radiodonts, present an important window into the evolution of arthropods and the development of Paleozoic ecosystems. Of these, a rare few species outside of Radiodonta possess lateral swimming flaps. The recent discovery of Utahnax provided much-needed insight into the evolution of swimming flaps, suggesting that the ventrolateral flaps of Kerygmachela evolved independently from other flap-bearing lobopodians and radiodonts. Here a new pelagic lobopodian species is described, Mobulavermis adustus new genus new species, the first lobopodian to be reported from the Cambrian-age Pioche Shale of Nevada. Mobulavermis adustus was large and possessed more ventrolateral flap pairs than any other known lobopodian or radiodont. It is found to be a close relative of both Kerygmachela and Utahnax, allowing the establishment of the new lobopodian family Kerygmachelidae new family. In addition, an indeterminate euarthropod fossil from the Pioche Formation is described in brief, and the recently described Chengjiang species Parvibellus avatus Liu et al., 2022, thought to have been related to the “gilled lobopodians,” is reinterpreted as a juvenile siberiid lobopodian.