Macroprimnoa ornata, Cairns, 2018

Cairns, Stephen D., 2018, Primnoidae (Cnidaria: Octocorallia: Calcaxonia) of the Okeanos Explorer expeditions (CAPSTONE) to the central Pacific, Zootaxa 4532 (1), pp. 1-43 : 19

Macroprimnoa ornata , n. sp.

Figs. 1I , 9 A–H

Etymology. Named ornata (Latin for decorated or adorned), an allusion to the somewhat ornate ridging on the body wall scales.

Types and Type Locality. Holotype: a complete colony, USNM 1463530 . Paratypes: EX 1708-2-1, 25.553˚N, 158.214˚W (topotypic), 3282 m, colony fragment, USNM 1467528 ; EX 1605-L 1-4-05, 11.41˚N, 144.78˚E ( Enigma Seamount , south of Guam, Northern Mariana Islands), 3643 m , colony fragment, USNM 1424086 ; EX 1606-13-03, 16.581˚N, 166.472˚E ( Batfish Seamount , south of Wake Island), 3066 m , colony fragment, SEM stubs 2386-2388, USNM 1424231 . Type Locality: EX 1708-2-GEO2-A2, 25.553˚N, 158.215˚W ( Beach Ridge , Musicians Seamounts), 3207 m .

Material Examined. Types; EX 1605-L1-13, 16.027˚N, 147.113˚E (off Saipan, northern Mariana Islands), 3676 m, image only .

Description. Colonies are unbranched (flagelliform), the holotype ( Fig. 1I ) an intact stem 8.7 cm in height supporting 12 polyps. A larger colony (USNM 1424086, paratype) was estimated to have been 27 cm in height at the time of collection). The polyps are uniserially arranged on one side of the stem and very widely spaced (1 polyp/cm), about 6–7 mm of branch coenenchyme between each polyp ( Fig. 1I ). The polyps stand perpendicular to the branch, are 3.5–3.7 mm in height, and are shaped as a squat cylinders topped with a conical operculum, which accounts for well over half of the height.

The body wall scales consist of eight longitudinal rows or two or three roughly rectangular (1.8–2.5 mm in width) scales, resulting in only 16–24 body wall scales ( Fig. 9 A–B). The body wall scales have a sinuous upper margin, sometimes similar to a Parastenella -like flute ( Fig. 9F ), and those nearest the branch often bear several vertical ridges on their outer surface ( Fig. 9H ). The proximal margin of the body wall scales bear a series or irregular digitiform processes.

The operculum is prominent ( Fig. 9 A–B), composing over half the height of the polyp. The symmetrical abaxial operculars are up to 3.1 mm in length, have an L:W of 2.6–3.1, and have a pointed tip and irregular lateral edges. The asymmetrical lateral operculars are only slightly shorter (2.5–2.7 mm) and have an L:W of about 1.6. The symmetrical adaxials are about 2.5 mm in length, with an L:W of about 1.9. All operculars ( Fig. 9G ) have a highly concave outer surface, a keeled inner surface, and a digitiform base, like the body wall scales, and are fragile.

The coenenchymal scales ( Fig. 9H ) are elongate (up to 3.3 mm in length with an L:W = 2.6–5.6), and usually pointed on both ends. Each coenenchymal bears tall (up to 0.5 mm, sail scales) ridges that sometimes coalesce into a network of interconnecting ridges.

Comparisons. Monotypic.

Remarks. The length of each pinnate tentacle is approximately 6.5 mm, with 16–18 pinnules on either side of each tentacle. This might explain why the polyps are so widely spaced and the opercular scales so long, but even so, tentacles from contiguous polyps overlap.

Distribution. Musicians Seamounts, northern Mariana Islands, and south of Wake Island, 3066–3676 m.

Figures

FIGURE 1. In situ images of various species: A, Callogorgia cracentis, holotype. B, Calyptrophora lyra, holotype (not in situ). C, C. diaphana, EX1606-9-1. D, C. carinata, holotype. E, C. clarki, EX1605-L3-6. F, C. pourtalesi, holotype. G, C. distolos, holotype. H, Candidella gigantea, EX1606-6. I, Macroprimnoa ornata, holotype. J, Narella virgosa, holotype. K-L, N. aurantiaca, holotype. M, N. merga, holotype. N, N. horrida, EX1703-2-3. O, N. fordi, holotype. P, N. calamus, holotype. Q, N. virgosa, paratype, EX1504-L4-9-4. R, N. macrocalyx, EX1606-7. S, N. hawaiiensis, EX1504-9-2. T, Paracalyotrophora hawaiiensis, EX1703-2-1. U, P. echinata, EX1703-10-1. V, P. spiralis, holotype. W, Plumarella circumoperculum, EX1603-2-3. X, Thouarella hilgendorfi, EX1605-L1-17.

FIGURE 9. Macroprimnoa ornata, paratype from USNM 142423: A–C, stereo views of lateral and opercular sides of a polyp. D, stereo view of coenenchymal scales, in situ. E, body wall scales, in situ. F, highly ridged body wall scales. G, opercular scales. H, ridged coenenchymal scales. Scale bars in mm.