Supporting Dataset S2 from Onychophoran-like musculature in a phosphatized Cambrian lobopodian

The restricted, exclusively terrestrial distribution of modern Onychophora contrasts strikingly with the rich diversity of onychophoran-like fossils preserved in marine Cambrian <i>Lagerstätten</i>. The transition from these early forebears to the modern onychophoran body plan is poorly constrained, in part, owing to the absence of fossils preserving details of the soft anatomy. Here, we report muscle tissue in a new Early Cambrian (stage 3) lobopodian, <i>Tritonychus phanerosarkus</i> gen. et sp. nov., preserved in the Orsten fashion by three-dimensional replication in phosphate. This first report of Palaeozoic onychophoran musculature establishes peripheral musculature as a characteristic of the ancestral panarthropod, but documents an unexpected muscular configuration. Phylogenetic analysis reconstructs <i>T. phanerosarkus</i> as one of a few members of the main onychophoran lineage—which was as rare and as cryptic in the Cambrian period as it is today.