Sarametra acuta, Mao & Zhang & Eléaume & Zhou & Zhang & Sun & Sha & Wang, 2025

Sarametra acuta sp. nov. ( Figs 7, 14)

ZooBank registration: urn:lsid:zoobank.org:act:.

Material examined: Holotype, RSIOCRI0272, Northwest Pacific, 12.6676°N, 156.5418°E, depth 1681 m, 22 July 2023, collected by HOV Jiaolong.

Diagnosis: A conical aboral pole on a conical centrodorsal with H/D = 1.8. Two or three columns of cirrus sockets per radial area separated by weak interradial ridges. The half of centrodorsal exhibits distinct spines, with some hook like, aligned along the interradial ridges and rims of obsolete sockets, forming continuous, spinose columns that extend to the apex. Radials and proximal brachials with short, protuberance-like spines.P 1 7.3–8.3 mm, 16 pinnulars. The first pinnular of P 1 with L/W = 1.3.

Description of holotype: Centrodorsal conical in shape. D = 3.9 mm, H = 7.1 mm, H/D = 1.8. Aboral pole is flat with a hole in the middle, probably eroded ( Fig. 14A). Cirrus sockets separated interradially by weak interradial ridges. Longitudinal series of sharp spines present along the interradial ridges of centrodorsal and between columns of obsolete socket. These spines are very prominent, and some even form hooks ( Fig. 14A, B).

Cirri XLIX (functional sockets). Functional cirrus sockets in two or three columns per radial area in basal half of centrodorsal. Each column of 4–6 functional sockets. Zero to four obsolete sockets per radial area. Fulcral bowl of cirrus sockets surrounding central lumen, with socket margins finely crenulate. Cirri of 49–60 segments, 30–40 mm long. Longest cirral L/W ratio is 2.9. c 1–4 are very short, measuring twice as wide as they are long. c 5–8 are the longest. Proximal cirrals cylindrical with distinctly concave aboral margins ( Fig. 14H). Opposing spine exists in some cirri. The terminal claw is tapered and exhibits a weak curvature.

The external ends of the basal are visible interradially. Radials short, with a shallow U-shaped distal margin decorated by short spines. Arms 10, more than 150 mm in length. Proximal brachials with short, protuberance-like spines ( Fig. 14C, E). IBr 1 short, W = 2.0 mm, L = 0.6 mm, W/L = 3.3. Distal margin of IBr 1 slightly raised from the axillary. Axillary (IBr 2) rhombic in shape, W = 2.6 mm, L = 1.7 mm, W/L = 1.5. The proximolateral and distal margins are slightly concave. IIBr 1 short, distal margin V-shaped, longer than proximal margin, W = 2.1 mm, L = 0.96mm, W/L = 2.1. IIBr 2 cuneate, W = 1.8 mm, L = 1.0 mm, W/L = 1.8.

First syzygy at IIBr 3 + 4, W = 1.5 mm. Second syzygy at IIBr 9 + 10, W = 1.8 mm. Syzygies at IIBr 3 + 4, IIBr 9 + 10 and IIBr 14 + 15; subsequent interval 4–6. IIBr 5–8 resembles a rectangle. Middle brachials W/L = 1.1–1.2. Brachials exhibit concave lateral margins and occasionally characteristic weakly alternating articular tubercles ( Fig. 14F, G).

Proximal pinnulars compressed, following pinnulars gradually narrower, becoming extremely slender to tip. Pinnule length 8.3–14.2 mm, 9–15 pinnulars. Pinnulars length 0.4–1.5 mm. P 1 7.3–8.3 mm 16 pinnulars. The first pinnular of P 1 with L/W = 1.3. P 1 wide at the base, getting thinner. Middle pinnular of P 1 L/W = 3.73. Distal pinnular of P 1 L/W = 4.0. P 2 up to 11.0 mm long with 19 pinnulars. Middle pinnular of P

2

L/W = 2.0. Distal pinnular of P 2 L/W = 3.8 ( Fig. 14F). The following pinnules have a broad base, the first pinnular is short, and the distal pinnulars are extremely slender ( Fig.14G).Pa 6.5–7.0mm, with11–14 pp.The distal pinnules are composed of oval-shaped and notably large pinnulars ( Fig. 14D).

Colour: Deep purple brown coloured ( Fig. 7F).

Etymology: The specific epithet ‘ acuta ’ is derived from the Latin word for ‘sharp’ or ‘pointed’, reflecting the sharp, prominent spine present on the centrodorsal in this new species.

Distribution: Known from Weijia seamount, Northwest Pacific. At 1681 m depth. Attached to Caulophacus sponge.

Remarks: A defining characteristic of this new species is the development of prominent spines along the interradial ridges and obsolete socket rims of the centrodorsal. In S. acuta , these spines are not only more pronounced than the cirrus sockets but also extend from the middle of the centrodorsal to the aboral pole, with some even developing into a hook. This distinctive morphology of the centrodorsal in Sarametra acuta provides a diagnostic characteristic that differentiates it from other species within the genus. In addition, the characters of P 1 distinguish it from Sarametra triserialis . The spines on the proximal brachials are also of a different shape as compared to what is observed in other species, as they form rows of small protuberance instead of long and sharp spines.