The scopelocheirid genus Aroui (Crustacea: Amphipoda: Lysianassoidea) with notes on the association between scopelocheirid amphipods, cassid gastropods and spatangoid echinoids
Formerly Aroui was a monotypic scopelocheirid genus known only from the Mediterranean Sea. The type species, Aroui setosus Chevreux, is redescribed. It is shown that a neotype, recently established for this species, is invalid, and a lectotype is selected from syntype material in the Museum National d'Histoire Naturelle, Paris. A second species, Aroui hamatopodus, is described, based on widespread collections from the Australian continental shelf and slope. The genus is rediagnosed and distinguished from all other scopelocheirids by two autapomorphic character states. Evidence is presented which suggests that scopelocheirids are very primitive scavengers, and that there is a three-way association between cassid gastropod predators, scopelocheirid amphipod scavengers and their common prey, spatangoid echinoids. An hypothesis is presented which suggests that scopelocheirid scavengers may have evolved by the early Tertiary and that the association involving cassid gastropods and spatangoid echinoids may date from this time.