Errina is a cosmopolitan genus of arborescent stylasterids that includes, discounting Errina cyclopora incertae sedis, 26 recent species and one extinct species. So far, only one species has been described from the Southwest Atlantic (SWA) off Argentina, Errina antarctica. Here, we describe a new species from that region, Errina argentina, collected in the Mar del Plata submarine canyon at 1398m depth. The new species is most similar to Errina kerguelensis in general growth form, arrangement of pores, and coenosteal texture, but differs in coenosteal strip width, gastrostyle and gastropore tube morphology, ampullae position, and the presence of numerous flush dactylopores. It differs from E. antarctica in coenosteum color, gastropore and dactylopore spine size, and shape of flush dactylopores. This record provides an extension of the present known distribution of the genus Errina in the SWA off Argentina.
