Data from: Molecular palaeontology illuminates the evolution of ecdysozoan vision

Colour vision is known to have arisen only twice – once in Vertebrata and
once within the Ecdysozoa, in Arthropoda. However, the evolutionary
history of ecdysozoan vision is unclear. At the molecular level, visual
pigments, composed of a chromophore and a protein belonging to the opsin
family, have different spectral sensitivities and these mediate colour
vision. At the morphological level, ecdysozoan vision is conveyed by eyes
of variable levels of complexity; from the simple ocelli observed in the
velvet worms (phylum Onychophora) to the marvellously complex eyes of
insects, spiders and crustaceans. Here we explore the evolution of
ecdysozoan vision at both the molecular and morphological level; combining
analysis of a large-scale opsin dataset that includes previously-unknown
ecdysozoan opsins with morphological analyses of key Cambrian fossils with
preserved eye structures. We found that while several non-arthropod
ecdysozoan lineages have multiple opsins, arthropod multi-opsin vision
evolved through a series of gene duplications were fixed in a period of 35
to 71 Million years (Ma) along the stem-arthropod lineage. Our integrative
study of the fossil and molecular record of vision indicates that fossils
with more complex eyes were likely to have possessed a larger complement
of opsin genes.