Comanthus scintillus, Obuchi & Fujita, 2017

Obuchi, Masami & Fujita, Yoshihisa, 2017, Comanthus scintillus, a New Species of Featherstar (Echinodermata: Crinoidea: Comatulida: Comatulidae) from Southern Japan, Species Diversity 22, pp. 201-206 : 203-205

publication ID	https://doi.org/ 10.12782/sd.22_201
publication LSID	lsid:zoobank.org:pub:BFB51880-2ABA-4DAA-9E46-23304BE0B5C4
persistent identifier	https://treatment.plazi.org/id/03C35666-FFCF-FFB9-1F1A-6C66FE27E67B
treatment provided by	Felipe
scientific name	Comanthus scintillus
status	sp. nov.

Treatment

Genus Comanthus A. H. Clark, 1908 Comanthus scintillus n. sp. ( Figs 1–3A, B View Fig View Fig View Fig ) [New Japanese name: Hanabi-Umishida]

Comanthus sp. : Fujita et al. 2015: 76, unnumbered fig. (RUMF-ZE-00437) in color.

Material examined. Holotype. OMNH-Iv6230, R 130– 70 mm, Nishidomari , Otsuki, Kochi Pref., southwestern Shikoku Island, Japan, 6.1 m depth, 20 July 2014, SCUBA, coll. M. Obuchi.

Paratypes. OMNH-Iv6231, R 150– 65 mm, same locality as holotype, 5.0 m depth, 10 June 2011; OMNH-Iv6232, R 155– 70 mm, same locality as holotype, 3.0 m depth, 21 July 2012; OMNH-Iv6233, R 115– 80 mm, same locality as holotype, 7.0 m depth, 16 April 2014; RUMF-ZE-00437, R 90– 45 mm, Shimajiriguchi, Kume Island, Ryukyu Islands , southwestern Japan, 6.8 m depth, 5 March 2005, SCUBA, coll . Y . Fujita; RUMF-ZE-00532: R 160– 60 mm, Maeda-misaki, Okinawa Island, Ryukyu Islands , 4.5 m depth, 22 November 1997, SCUBA, coll . Y . Fujita.

Other materials. OMNH-Iv6234, R 85– 50 mm, same locality as holotype, 15.0 m depth, 11 November 2013; OMNH-Iv6235, R 100– 65 mm, same locality as holotype, 5.0 m depth, 15 July 2016; BIK-EC-CR0091, R 135– 70 mm, same locality as holotype, 3.0 m depth, 6 May 2014; BIK- EC-CR0092, R 135– 70 mm, same data as BIK-EC-CR0091 except depth, 1.7 m; BIK-EC-CR0093, R 180– 90 mm, same locality as holotype, 5.6 m depth, 6 July 2014; BIK- EC-CR0095, R 105– 45 mm, same locality as holotype, 9.3 m depth, 28 July 2014; RUMF-ZE-00432, R 90– 35 mm, Takenchi , Kume Island, Ryukyu Islands, 11.3 m depth, 4 March 2005, SCUBA, coll . Y . Fujita; RUMF-ZE-00438, R 130– 60 mm, Garasaa-oki , Kume Island, Ryukyu Islands, 9.2 m depth, 6 March 2005, SCUBA, coll . Y . Fujita; RUMF- ZE-02005, R 60 mm, Shimoji Island , Miyako Island Group, Ryukyu Islands, 18.0 m depth, 15 March 2006, SCUBA, coll . Y . Fujita.

Comparative materials. Comanthus gisleni Rowe, Hoggett, Birtles, and Vail, 1986 : BIK-EC-CR0107, R 135– 55 mm, Cape Zanpa, Yomitan, Okinawa Island , the Ryukyu Islands, Japan, 13.0 m depth, 30 April 2017, SCUBA, coll . M . Obuchi . Comanthus suavia Rowe, Hoggett, Birtles, and Vail, 1986 : BIK-EC-CR0096, R 175– 95mm, Nishidomari, Otsuki, Kochi Pref ., southwestern Shikoku Island , Japan, 4.6 m depth, 4 May 2013, SCUBA, coll . M . Obuchi.

Diagnosis. A medium-sized species with anterior arm length 100–150 (to 180) mm. Centrodorsal small, thin discoidal. Cirri weak, II–IX, 11–16 segments, 5.5–8.0 mm long, arranged in single row with gaps; longest cirrals 1.3 times longer than broad; distal cirrals with low transverse ridge. Radials narrowly exposed. Arms 21–38 in number; anteri- or arms about twice as long as posterior. IIBr and IIIBr of mostly 4(3+4), rarely 2; each division series well separated, except first ossicle of each in lateral contact interiorly. First arm syzygy at br 3+4, second at br 9+10 to br 11+12, and following at 4 intervals of muscular articulations. Pinnules on division series and P 1 longest; P 2 shortest, about half length of P 1; following gradually longer; distal pinnules slender, with distal fringe of spines on middle segments, but sometimes indistinct. Terminal combs of 6–11 teeth, always present to P 2 and at intervals to P 11 –P 18, about proximal third of anteri- or arms; teeth large, triangular, confluent, basally in contact, without secondary teeth; proximal segment with transverse spoon-like tooth; terminal segment with discrete tooth. In life, whole body red with scattered small yellow spots.

Description of holotype. Centrodorsal small, thin, stellate, 3.2 mm across, slightly raised above level of radials ( Figs 1A View Fig , 2C View Fig ); polar area smooth, slightly concave at center, about 0.7 times as wide as centrodorsal; few cirri and obsolete sockets present at margin.

Cirri weak, III, plus V rudimentary, 15 segments, 6.5– 7.0 mm long, arranged in single row ( Fig. 1A, B View Fig ); c 1 short, cylindrical; c 2 –c 3 as long as wide; c 4 –c 7 longest, L/W up to 1.2; followings decreasing in length; distal margin of distal cirrals aborally thickened, becoming transverse ridge on 3–5 segments preceding penultimate; penultimate L/ W 0.6, with small conical, occasionally transversely chisel-shaped, opposing spine on distal part; terminal claw curved, pointed, and slightly longer than penultimate.

Radials narrowly exposed, not exceeding 0.2 times as long as centrodorsal ( Figs 1A View Fig , 2C View Fig ). Each division series well separated, except first ossicles laterally united interiorly. IBr series of 2 ossicles; Ibr 1 short, oblong, W/L 3.3; Ibr 2 pentagonal with short lateral margins, W/L 2.2. Ten IIBr series all 4(3+4); IIbr 2 bearing PII. Twelve IIIBr series all 4(3+4); IIIbr 2 bearing PIII.

Arms 32. Anterior arms 123 mm long; posterior arms 60 mm long. Proximal brachials short; br 1 W/L 2.1, interiorly united with neighbor; br 2 trapezoid with longer exterior margin, W/L 2.5, totally separated from neighbor, bearing P 1; br 3+4, united by first arm syzygy, oblong, W/L 1.9; br 4 bearing Pa; br 5 –br 7 cuneate, W/L 1.8–2.3. Middle brachials triangular thickened at distal margin, gradually becoming cuneate again distally. Distal brachials of anterior arms elongated, cylindrical, W/L 0.4, smooth; brachials of posterior arms shorter, with W/L 0.6–0.8. Second arm syzygy at br 9+10 to br 11+12; following syzygies at 4 intervals of muscular articulations.

Pinnules on division series and P 1 similar, longest, composed of 35–40 segments, 12.0–13.0 mm long ( Fig. 1C View Fig ); proximal four to five pinnulars rhombic, broader than long; following cylindrical, as broad as long. P 2 shortest, composed of 22–26 segments, 5.0– 6.5 mm long; all pinnulars broader than long. P 3 same length as, or slightly longer than P 2, composed of 18–25 segments, 5.0– 6.5 mm long, first genital pinnule; all pinnulars broader than long, with fine spines on aboral side. Following middle pinnules to P 12 –P 16 similar to P 3, successively becoming longer; P 4 of 24–27 segments, 6.0–8.0 mm long; P 5 of 15–16 segments (no terminal comb), 6.5–7.0 mm long. Distal pinnules on anterior arms slender, composed of 19–22 segments, 8.5–10.0mm long; middle segments L/ W 3.0, with fringe of distal spines ( Fig. 3A View Fig ); spines sometimes indistinct ( Fig. 3B View Fig ); pinnules on posterior arms shorter, almost same length as or slightly longer than middle pinnules on same arm.

Terminal combs consisting of 6–11 teeth, always present to P 2 and at intervals to P 11 –P 18, about proximal one third of anterior arms and half of posterior arms ( Fig. 1D View Fig ); teeth large, triangular, curved inward, basally in contact, confluent with exterior side of pinnular; proximal segment with transverse spoon-like tooth; terminal segment with discrete tooth not fused to others; no secondary teeth.

Disk rounded, 14 mm diameter, four to eight times as wide as centrodorsal, largely smooth but with fleshy conical papillae on anal cone ( Fig. 2D View Fig ); mouth marginal; anal cone central.

Notes on other materials. Large specimen (RUMF- ZE-00532, paratype): centrodorsal 2.8 mm across; cirri VII, plus III rudimentary, to 14 segments, 7.5 mm long; eight IIBr series 4(3+4), and two of 2; most IIIBr series 4(3+4), and one of 2; arms 36, 155– 55mm long; terminal combs distributed to P 12 –P 14 at intervals; disk 15 mm across.

Small specimen (OMNH-Iv6234): centrodorsal 2.3 mm across; cirri IX, plus II rudimentary, to 13 segments, 7 mm long; all IIBr and IIIBr series 4(3+4); arms 21, 80– 45 mm long; terminal combs to P 10 –P 14 at intervals; disk 5 mm across.

Juvenile specimen (RUMF-ZE-02005): radials more exposed, length one third of centrodorsal diameter; arms 13, 60 mm long; terminal comb to P 2 –P 4.

Habitat and feeding posture. Dwelling within infrastructure of rocky reefs or between branches of stony corals ( Fig. 2A View Fig ). Anterior arms extended with pinnules arranged alternately to make two planes along each side of arms (multidirectional posture of Meyer and Macurda (1980)).

Color in life. Uniformly red with scattered small yellow spots ( Fig. 2 View Fig ); distal arms and pinnules often almost yellow with dense spots ( Fig. 2B View Fig ).

Distribution. From southwestern Shikoku Island to the Ryukyu Islands, southern Japan: Ashizuri-Uwakai Sea, Okinawa Island, Kume Island, and Shimoji Island of Miyako Island Group. Depth range subtidal to 18 m.

Etymology. The specific name scintillus indicates spark from Latin, named after its impressive coloration in life, in which scattered yellow spots are associated with sparks.

Remarks. Comanthus scintillus n. sp. is diagnosed by the following characters: (1) the centrodorsal is small with few cirri; (2) terminal combs occur to the middle of the arms; (3) middle segments of distal pinnules bear a distal fringe of spines, and (4) secondary comb teeth are absent. The new species seems most closely related to Comanthus gisleni in that both have a distal fringe of spines on the middle segments of the distal pinnules ( Fig. 3C View Fig ). However, in C. gisleni , the terminal combs are distributed to the distal pinnules on the arm tip (see Rowe et al. 1986). Distribution of the combs distinguishes the new species from Comanthus parvicirrus and Comanthus kumi , which both have combs to near the arm tips as in C. gisleni ( Rowe et al. 1986; Fujita and Obuchi 2012). The new species shares with Comanthus suavia combs as far as the middle of the arms: up to P 18 and P 15 respectively, and more restricted in small specimens of both species ( Rowe et al. 1986). However, C. suavia lacks cirri in mature specimens, and has radials largely exposed, and distinct secondary comb teeth. In addition, in C. suavia , middle segments of the distal pinnules are distally smooth without spines ( Fig. 3D View Fig ). When living, C. scintillus n. sp. can be easily recognized by the unique coloration. The spotted pattern is similar to some individuals of Comatella stelligera (Carpenter, 1888) , rather than other members of Comanthus (see Obuchi 2016: pl. 1A).