The morphology of the eyes of the olenid trilobite Jujuyaspis keideliKobayashi, 1936, is described and illustrated. Studied specimens come from Early Tremadocian pyritiferous black shales of the Casa Colorada Formation (=Purmamarca shales) at Purmamarca, Jujuy Province, northwestern Argentina. The eyes are holochroal and proportionately large relative to the overall size of cephalon. They are always found attached to the librigena, showing no preserved lenses, only molds of their surfaces. Their molds demonstrate that lenses were numerous, biconvex, hexagonal in outline and arranged in an hexagonal close-packing system. The eye curvature and the disposition of the facets covering all the visual surface indicate that Jujuyaspis keideli Kobayashi had a visual field wider than that of most benthic olenids. The pattern of lens arrangement and the poorly developed peripheral zone support pelturine affinities for the species.

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