Kokosaster acanthodes, Mah, 2025

Kokosaster acanthodes View in CoL nov. gen. nov. sp.

Figures 11A–G

Material Examined. Holotype. NMV F307960 About NMV . Cocos (Keeling) Islands, Indian Ocean Territory , 12º 13 ‘ 32" S, - 12º 14' 21" S to 96º 57' 36" E, - 96º 58' 16" E 1113–1343 m. Coll. O’Hara et al. RV Investigator 17 October 2022. 1 wet spec. R = 3.9 r = 2.3 GoogleMaps

Paratypes. NMV F307959 About NMV . Cocos (Keeling) Islands Territory , Australia. 12º 13' 32" S, 12º 14' 21" S to 96º 57' 36" E, - 96º 58' 16 “ E, 1113–1343 m. Coll. Tim O’Hara et al. IN 2022 GoogleMaps V 08IOT 2, Marine Invertebrates Team, 17 October 2022. 1 wet spec . R = 3.8 r = 2.1

NMV F307961 About NMV . Cocos (Keeling) Islands Territory , Australia. 12º 13' 32" S, 12º 14' 21" S to 96º 57' 36" E, - 96º 58' 16" E, 1113–1343 m. Coll. Tim O’Hara et al. IN 2022 GoogleMaps V 08IOT 2, Marine Invertebrates Team, 17 October 2022. 1 wet spec . R = 3.5 r = 1.8.

Etymology. The genus, Kokosaster is named for the type locality, the Cocos Islands (spelled Pulu Kokos in Cocos Malay). The species epithet acanthodes alludes to the numerous spines present on the actinal plates.

Diagnosis. Body stout, inflexible, weakly stellate, R/r = 1.69, arms wide at base, arm tips blunt. Interradial arcs weakly curved. Abactinal plates flat to weakly convex covered by granules, 5 to 30, mostly 15 to 20, Peripheral granules elongate different from round/irregularly polygonal granules elsewhere. Marginal plates 18/20 superomarginal/inferomarginal. Superomarginal surface bare, inferomarginals bare distally, but with granules proximally. Granules present interstitially between superomarginals and inferomarginals. Actinal plates covered with short spinelets, 1 to 6, mostly 4 to 5 conical present centrally on each plate especially on those close to inferomarginal plates. Furrow spines 6, with two series of 3 conical subambulacral spines, widely spaced.

Comments. Characters on Kokosaster acanthodes nov. gen. nov. sp. appear intermediate between other pentagonal shaped Goniasteridae , such as Peltaster (granular covered abactinal plates) and Alloceramaster (smooth superomarginal plate surface, differing peripheral granules around the abactinal plates of the papular region). The actinal spination, showing spines with blunt tips as expressed on Kokosaster could not be located on other goniasterid taxa, in contrast to taxa such as Calliaster and Calliderma that show distinct, pointed conical spines present on the actinal surface ( Fig. 11F). However, similar types of spines are found on the actinolateral boundary of the inferomarginal plates on Ahuastra gfoei ( Mah, 2020) .

Occurrence/Distribution. Cocos Keeling Islands, Indian Ocean Territory, 1113–1343 m.

Description. Body rigid, weakly stellate, R/r = 1.69–1.8, arms wide at base, arm tips blunt. Interradial arcs weakly curved ( Fig. 11A).

Abactinal plates polygonal with more plates more distinctly hexagonal along radial regions, more irregularly polygonal and smaller shaped interradially adjacent to the superomarginal plates. Abactinal plates restricted to disk, absent from distalmost arm regions where superomarginal plates are abutted. Plates flat to weakly convex, covered by granules, 5 to 30 flattened, weakly polygonal, close but evenly arranged in linear series ( Fig. 11A–C). Where granules are absent, shallow concavities are present. Peripheral granules of two types, weakly polygonal granules present around interradial plates and elongate, rod-shaped granules, approximately 25–30 total, 5 per side, present around radial plates, papular regions in three series. Papulae around proximal arm regions, absent distally and interradially. Madreporite quadrate in shape, flanked by four plates. Small paddle-shaped pedicellariae, approximately 1.0 mm in length, variably present.

Superomarginal plates 16 to 18 per interradius (arm tip to arm tip) at R = 3.5, 20 inferomarginal plates ( Fig. 11A, D). Superomarginal plates wide, blocky curved abactinal-lateral edge, forming approximately 13% of the total “r” distance (0.3/2.3). Distalmost four superomarginals abutted along arm midline. Superomarginal plate surface completely bare on dorsal and lateral surface. Inferomarginal plates with ventralfacing bare patch, covered by granules on lateral surface. Peripheral granules, round present in interstitial regions, forming two to four series especially at contact between superomarginal and inferomarginal plates. No pedicellariae.

Actinal plates in four, full series, chevron-like series. Plates quadrate in shape with rounded edges. Fasciolar grooves shallow. Actinal plates with spines, blunt, short, and pointed, 1 to 6 present centrally on each plate ( Fig. 11F). One paratype with much shorter spines, comparable in height to adjacent granules. Peripheral granules, approximately 3 to 4 per side, 12–18 total, each quadrate to polygonal in cross-section, shorter than actinal spines. Actinal plate surface otherwise bare. No pedicellariae. Inferomarginal plates with pointed conical spinelets similar to others on actinal plate surface on surface adjacent to actinal surface. Actinal surface adjacent to inferomarginal plates with blunt spinelets. Paddle-like pedicellariae variably present on actinal plate surface, 2 to 6, per interradius.

Furrow spines 5 to 6, mostly 6, blunt, laterally flattened, subambulacral spines in two series, three spines each, conical, pointed, widely spaced with central spine most prominent ( Fig. 11G). Further adambulacral granules, 4 to 8, short, irregularly pointed to rough. Oral plates with furrow spines, 12 and a single prominent spine, quadrate in shape, blunt tipped directed into the mouth (a total of 2 per interradius). Oral plate surface with 7 prominent elongate pointed spines (identical to subambulacral spines) and 7 shorter spines, quadrate in cross-section, paired on either side of the central diastema between the oral plate sides. 6 to 8 granules similar to those on actinal surface on remaining oral plate surface.