Fig. 4.

A panarthropod phylogenetic tree with diagrammatic summary of central nervous system (CNS) and evolution of visual structures within Panarthropoda. a Diagrammatic representation of the CNS in panarthropod lineages, with the inferred CNS condition in the last common ancestor (LCA) of panarthropods. Although it is not unequivocal, the lack of segmental ganglia in the trunk of onychophorans⁷ and the stem-group euarthropod Lyrarapax¹ suggests that segmental ganglia were absent in the LCA of panarthropods. b Visual structures of different panarthropod lineages. The diagrammatic representations of the visual organs of Tardigrada and Onychophora are modified from ref.¹³. “Cambrian lobopodians” is also referred to as xenusians in the literature³⁷. The polytomy in this cladogram represents the unresolved phylogenetic relationship among Tardigrada, Onychophora, “Cambrian lobopodians,” and the total-group euarthropods