Aquilonastra cassini, O’Loughlin, 2015

O’Loughlin, P. Mark, 2015, New asterinid seastars from northwest Australia, with a revised key to Aquilonastra species (Echinodermata: Asteroidea), Memoirs of Museum Victoria 73, pp. 27-40 : 35

Aquilonastra cassini sp. nov.

Zoobank LSID. http://zoobank.org/ urn:lsid:zoobank.org:act:

EBFF184D-ADAE-4C5C-AA63-619D69B4AE4A

Material examined. Holotype. North Western Australia, Kimberley Region, Woodside Collection Project (Kimberley) 2008–2015, station 37/K10, Cassini I., 13.95156S - 125.624123E, rock substrate, 3 m, coll. L. Walker, 18 Oct 2010, WAM Z26198 (one ray cut off proximally and cleared).

Paratype. Woodside Collection Project (Kimberley) 2008–2015, station 33/K10 (see database), Cassini Island, 13.92816 S - 125.623337 E, lagoon, rock substrate, 1.8 m, coll. A. Sampey et al., 17 Oct 2010, WAM Z26201 (1) (one ray cut off proximally and cleared) .

Description. Asterinid seastar, asymmetrical, five or 6 sub-equal rays, sub-digitiform, narrow and rounded distally, slightly widened basally, up to R = 7.0 mm, r = 2.5 mm, rays merging at bases, inter-radial junction of rays sub-acute, rays low convex abactinally, rays slightly convex actinally, margin acute. Disc not discretely demarcated. Three small, inconspicuous, abactinal madreporites seen on holotype. Fissiparous. No abactinal or actinal gonopores detected. Pedicellariae not detected. Glassy convexitiesonclearedabactinalandactinalplates.Inferomarginal plates significantly larger than superomarginal plates; inferomarginal plates project noticeably at margin. Internal superambulacral and superactinal plates present.

Abactinal surface: disc plates imbricate irregularly with those of upper rays; upper ray plates proximal to disc irregular; lacking secondary plates; regular carinal series of plates along some upper rays only, up to 11 carinal plates per series, each carinal plate with paired deep lateral notches to create paired single papular spaces; plates on sides of rays with single papular space; single series of papulae adcarinally on rays, up to 15 per series, short lower series of smaller papulae along rays, 4 prominent longitudinal series of papulae across rays; abactinal spinelets predominantly conical; disc with 6–3 spinelets per plate, each carinal plate with cluster of 5–3 spinelets on crown of plate, adcarinal plates with up to 7 spinelets across angled plate, proximal and distal inter-radial abactinal plates with predominantly 4 spinelets, variably 6–3, conical to splay-pointed; superomarginal plates with 5–4 splay-pointed spinelets per plate.

Actinal surface spines per plate: oral 4–3, sub-oral 1–0, digitiform, slightly spatulate, with minute distal spinelets; proximal furrow 4–3, subambulacral 3–2; actinal predominantly 4, conical form with pointed distal end; inferomarginal up to about 11, predominantly splay-pointed, frequently with 2 and 6 abactinalinferomarginalgroups,3conicalactinalinferomarginals. Actinal plates in longitudinal and more noticeably oblique series.

Distribution. North Western Australia, Kimberley Region, Cassini Island, rock substrate, 1.8– 3 m.

Etymology. Named cassini (in apposition) for the type locality, Cassini Island, in the Kimberley Region of north Western Australia.

Remarks. The subequal ray lengths of the five-rayed holotype prompted us to not think fissiparity for this species. But the presence of three small madreporites on the holotype, and irregular abactinal plate arrangement, lead us to conclude that this species is fissiparous. It differs in particular from other species of Aquilonastra from the Kimberley region by having a combination of: 5–6 rays; predominantly conical abactinal spinelets; up to 3 madreporites; fissiparous habit; absence of pedicellariae.