A relict Triassic brittle star (Echinodermata: Ophiuroidea) in the Lower Jurassic of Asturias, Spain

Abstract Ophiuroids, also called brittle stars, are an important component of modern marine benthos, yet their fossil record is still poorly understood. Here, we describe new finds of ophiuroids from the Upper Sinemurian (Lower Jurassic) of Asturias, Spain. The material consists of several articulated specimens showing all relevant anatomical details to allow for an exhaustive description. The specimens belong to a new species, Arenorbis santameraensis sp. nov., adding a Jurassic species to the genus Arenorbis previously known exclusively from the Middle Triassic of central Europe. We show that Arenorbis has characters typically found in the suborder Ophiodermatina. The new Jurassic occurrence of Arenorbis shows remarkable parallels with its Middle Triassic equivalents in terms of sedimentologic and taphonomic context, suggesting niche conservatism in Arenorbis . In contrast to the wide geographical distribution of the genus in the Middle Triassic, the new species is currently only known from a restricted area, suggesting that it represents a Jurassic relict of a formerly widespread Triassic lineage.