Relict from the Jurassic: new family of brittle-stars from a New Caledonian seamount.

The deep-seafloor in the tropical Indo-Pacific harbours a rich and diverse benthic fauna with numerous palaeoendemics. Here, we describe a new species, genus and family of brittle-star (Ophiuroidea) from a single eight-armed specimen collected from a depth between 360 and 560 m on Banc Durand, a seamount east of New Caledonia. Leveraging a robust, fossil-calibrated (265 kbp DNA) phylogeny for the Ophiuroidea, we estimate the new lineage diverged from other ophiacanthid families in the Late Triassic or Jurassic (median = 187-178 Myr, 95% CI = 215-143 Myr), a period of elevated diversification for this group. We further report very similar microfossil remains from Early Jurassic (180 Myr) sediments of Normandy, France. The discovery of a new ancient lineage in the relatively well-known Ophiuroidea indicates the importance of ongoing taxonomic research in the deep-sea, an environment increasingly threatened by human activities.