Clarkcomanthus littoralis ( Carpenter, 1888 )

Obuchi, Masami, 2020, Shallow-water Comatulids (Echinodermata: Crinoidea: Comatulida) of the Ashizuri-Uwakai Sea, Shikoku Island, Southern Japan, Species Diversity 25, pp. 309-328 : 316-317

15. Clarkcomanthus littoralis ( Carpenter, 1888) [Japanese name: Kuraaku-umishida]

Morphology. Centrodorsal flat, pentagonal, 2.9–3.9 mm across, at almost same level of radials; polar area 0.6–0.8 times of centrodorsal diameter. Cirri weak, 0–XI, most of which rudimental, up to 15 segments, 11.5 mm long, arranged in single row with gap; c5–6 longest, L/ W 1.4; distal segments with aboral process. Radials exposed, length less than 15% of centrodorsal diameter. IBr series composed of 2 ossicles, IIBr of 2 or 4(3+4), and III–IVBr of mostly 4(3+4), rarely 2. Arms up to 51, 160 mm long; anterior arms sometimes distinct, 1.7 times longer than posterior; first arm syzygy at br 3+4; distal intersyzygial intervals 4. Comparative pinnule length PD > P 1 >>P 2 =P 3 =P 4 =P 5; PD to P 1 enlarged, with segments broader than long; segments of pinnules beyond P 3 with distal-oral edge projected like spine . Terminal combs present as far as P 1–2, consisting of 6–9 segments; tooth usually paired, rarely single; primary tooth confluent with lateral margin, straight, widely spaced from adjacent one; secondary tooth much smaller; terminal and proximal segments diminished discrete tooth. Disk four to five times as wide as centrodorsal.

Posture. Nocturnal. Hiding under overhangs or between foliose corals. Some arms extended in multidirectional posture at nighttime.

Coloration in life. Rays grey to black, with narrow stripes of white articulation, often distally whitish.

Distribution. Ashizuri-Uwakai Sea, Japan (present study) to Great Barrier Reef. Tonga to West Australia ( Rowe et al. 1986). North Mariana Islands ( Kirkendale and Messing 2003).

Remarks. The examined specimens were identified by the oral pinnules with broad segments, and the terminal combs restricted to P 3 and composed of paired small teeth not fused at distal-most segments. Compared to the specimen from the Ryukyu Islands, the examined specimens were generally smooth: projections on distal end of brachials and on distal-oral edge of pinnule segments were less developed. Rowe et al. (1986) recognized three groups in the specimens from Australia on the basis of coloration. Specimens from the Ryukyu Islands with green to yellow coloration agreed with the group including the holotype, while the group to which the examined specimens refer to was unclear.