Stylasterids (Hydrozoa: Stylasteridae) from Mar del Plata submarine canyon and adjacent area (southwestern Atlantic), with a key to the species off Argentina Bernal, M. C. Cairns, S. D. Penchaszadeh, P. E. Lauretta, D. Zootaxa 2021 2021-05-12 4969 3 401 452 7NSK3 Cairns, 1983 a Cairns 1983 [238,601,1806,1833] Hydrozoa Stylasteridae Cheiloporidion Animalia Anthoathecata 2 3 Cnidaria genus    Typespecies.  Cheiloporidion pulvinatum Cairns, 1983a  Included species.  Cheiloporidion pulvinatum   Distribution.SWA off Argentinafrom Mar del Plata to Tierra del Fuegoand Cape Horn. Depth: 642–1137 m(see Cairns 1983a). New record off Mar del Plata, 852–1289 m.   Diagnosis(from Cairns 1983b; changes in bold). Colonies uniplanar with a strong tendency toward branch anastomosis, producing a network of irregularly shaped fenestrae. Branches elliptical to rectangular in cross section, the greater axis perpendicular to the plane of branching. Branches ridged on both anterior and posterior faces. Coenosteum reticulate, composed of short discontinuous strips, which are smooth or granularand have rounded edges. Dactylopores occur randomly on anterior and lateral branch surfaces; gastropores loosely aligned along lateral edges. Gastro- and dactylopore tubes short, branches compact. Gastropores flush with branch surface; gastrostyles ridged, bearing fused spines. Dactylopores rimmed by two to four vertical platelets, which form a discontinuous collar around the pore; no dactylostyles. Ampullae superficial. Soft parts unknown.