Clarkcomanthus Rowe, Hoggett, Birtles & Vail, 1986

Summers, Mindi M., Messing, Charles G. & Rouse, Greg W., 2017, The genera and species of Comatulidae (Comatulida: Crinoidea): taxonomic revisions and a molecular and morphological guide, Zootaxa 4268 (2), pp. 151-190 : 176-180

Clarkcomanthus Rowe, Hoggett, Birtles & Vail, 1986

Table 1; Figs. 12–14

Type species. Comanthus luteofuscum HL Clark, 1915.

Other included taxa (7). Actinometra alternans Carpenter, 1881 ; Actinometra littoralis Carpenter, 1888 ; Clarkcomanthus albinotus Rowe, Hoggett, Birtles & Vail, 1986 ; Comanthus mirabilis Rowe, Hoggett, Birtles & Vail, 1986 ; Comanthus perplexum HL Clark, 1916; Comanthus (Vania) parvicirra ß comanthipinna Gislén, 1922; Oxycomanthus exilis Rowe, Hoggett, Birtles & Vail, 1986 ; Oxycomanthus mirus Rowe, Hoggett, Birtles & Vail, 1986 .

Diagnosis. Mouth excentric in fully developed individuals; up to 125 arms; centrodorsal circular to pentagonal; cirri in one row or absent ( Figs. 12 E–F, 12J, 12L–M, 13C–H, 13K–M, 13Q, 13S); IBr2 united by synarthry; IIBr and subsequent brachitaxes 2 or 4(3+4); first syzygy at 3+4 on all undivided arms; distal intersyzygial interval 4; distalmost pinnule comb on P2, P3, or at intervals sometimes reaching near arm tip; comb terminating in large discrete tooth, or tapering either to a smaller terminal tooth or to a point; primary comb tooth confluent with exterior edge of pinnulars or nonconfluent; smaller secondary tooth present or not; transverse proximal tooth present or not ( Fig. 13 I–J, N, R, T).

Distribution. Tropical and warm temperate Indo-western Pacific from northern Australia (Lancelin, WA, to Byron Bay, NSW), east to Kwajalein ( C. alternans identified as Comanthus briareus in Zmarzly 1985 ), Fiji and Tonga, and north to Sagami Bay, Japan. Except for western Australia and Indonesia, no reliable records are yet known from the Indian Ocean (AH Clark 1931; Kogo & Fujita 2014; Rowe et al. 1986; Rowe & Gates 1995; Zmarzly 1985). Depth range: 0–144 m; chiefly shallower than 50 m.

Molecular results. Summers et al. (2014a) expanded Clarkcomanthus to contain eight clades as species-level taxa. All but one was assignable to an available species name (uncorrected distances of COI minimally>2.8% between each) ( Fig. 14 ). In addition to the three species previously included in Clarkcomanthus , two each were formerly assigned to Comanthus ( C. alternans , C. mirabilis ) and Oxycomanthus ( O. comanthipinnus , O. mirus ). The unnamed clade included only one specimen identified in the field at Raja Ampat , Indonesia, as Oxycomanthus exilis . Those assignable to descriptions of Australian Clarkcomanthus exilis and Cl. comanthipinnus also formed a clade with intra specific divergence <0.3%, suggesting that Australian comanthipinnus and exilis are the same species. Although we did not sequence specimens from near the type locality of O. comanthipinnus ( Bonin Islands , Japan), the identifications are unambiguous, and exilis appears to simply be smaller specimens of comanthipinnus . Multiple specimens assigned morphologically to Clarkcomanthus littoralis based on Rowe et al. (1986) nested within a clade of specimens identified as Cl. albinotus (intra specific divergence <2.3%).

Remarks. The taxa included in Clarkcomanthus possess a wide variety of comb structures, e.g., teeth paired or not, confluent or not, tapering to a point or not, and with a transverse proximal tooth or not. Unlike Comanthus , however, Clarkcomanthus species share combs restricted to the most proximal few pairs of pinnules [although a few combs sometimes occur beyond mid-arm in Cl. alternans (Rowe et al. 1986) ]. Also, although Cl. alternans and Cl. mirabilis have a transverse proximal comb tooth as in Comanthus species, the following teeth are well separated, unlike the triangular, basally abutting teeth in Comanthus species.

Clarkcomanthus is most abundant along the reef crest and in shallow water. Members showcase incredible morphological variation, especially in color patterns, leading us to suggest that robust identifications should incorporate genetic information. Within Clarkcomanthus , cirri are uniformly absent in Cl. mirabilis and Cl. littoralis (see below), and are lost with development in Cl. alternans and, possibly, Cl. mirus (Rowe et al. 1986) .

Figures

FIGURE 12. Clarkcomanthus. (A – F) Clarkcomanthus mirabilis— (A – D) live, on reef, fully exposed (A, C) or semicryptic (B, D), illustrating color variations; (E – F) aboral surface, showing different color patterns and small, acirrate centrodorsal. (G – M) Clarkcomanthus alternans— (G, H, I, K) live, exposed on reef, (J, L) aboral views, showing small centrodorsal with no cirri, exposed radials, and overlapping division series and arm bases, (M) aboral view of small specimen with larger centrodorsal bearing few cirri and covering most of radials, and fewer non-overlapping arms. Madang, Papua New Guinea: A. MNHN-IE- 2013 - 8158; B. MNHN-IE- 2013 - 8111; C. MNHN-IE- 2013 - 8162; E. MNHN-IE- 2013 - 8086; F. not vouchered, SIO-BIC E 5973 (DNA subsample); G. MNHN-IE- 2013 - 8180; I. MNHN-IE- 2013 - 8055; J. MNHN-IE- 2013 - 8173; K. MNHN-IE- 2013 - 8173; L. not vouchered, SIO-BIC E 5968 (DNA subsample). Timor: D. AM J. 25411. Raja Ampat, Indonesia: H. not vouchered (RA 226); M. SIO- BIC E 6219.

FIGURE 13. Clarkcomanthus. (A – J) Clarkcomanthus albinotus— (A) live, oral view following extraction from rubble; (B) semicryptic under ledge; (C – H) aboral views; (I – J) short combs tapering near tip, with J showing paired confluent comb teeth. (K – L) Clarkcomanthus luteofuscum, aboral surface showing rounded centrodorsal with row of cirri. (M – N) Clarkcomanthus cf. littoralis — (M) aboral surface showing centrodorsal with no cirri; (N) comb with separated confluent teeth, smaller near tip. (O – R) Clarkcomanthus comanthipinnus— (O, P) live, oral view following extraction from rubble; (Q) aboral surfaces showing rounded centrodorsal with few cirri at interradials; (R) comb tapering to distal point, composed of separated nonconfluent teeth. (S – T) Clarkcomanthus mirus— (S) aboral surface showing centrodorsal with cirrus buds at interradials; (T) comb tapering to blunt tip, composed of separated nonconfluent teeth. Madang, Papua New Guinea: A. MNHN-IE- 2013 - 8060; B, C. MNHN-IE- 2013 - 8122; D. MNHN-IE- 2013 - 8068; K. MNHN-IE- 2013 - 8184; O. MNHN-IE- 2013 - 8082; P. MNHN-IE- 2013 - 8151. Raja Ampat, Indonesia: E. SIO-BIC E 6186; F. SIO-BIC E 6187; G, I. SIO-BIC E 6190; L. SIO-BIC E 6210; M, N. SIO-BIC E 6193. South Island, near Lizard Island, Australia: H, J. AM J 17360; holotype. Lizard Island, Australia: Q-R. AM J 16992, holotype; S, T. AM J 17202, holotype.

FIGURE 14. Maximum likelihood tree of Clarkcomanthus inferred from COI. Symbols, location abbreviations, and labels as in Figure 2. New COI sequences are Genbank KR 010190 - KR 010244.