Sarametra A.H. Clark, 1917

Mao, Jingwen, Zhang, Ruiyan, Eléaume, Marc, Zhou, Yadong, Zhang, Dongsheng, Sun, Shao’e, Sha, Zhongli & Wang, Chunsheng, 2025, Description of three new species of Zenometridae (Echinodermata, Crinoidea, Comatulida), with new insights on species and genus delimitation, Zoological Journal of the Linnean Society 204 (4) : -

Genus Sarametra A.H. Clark, 1917

Revised diagnosis: A genus of Zenometridae with a conical or truncated conical centrodorsal. Peripheral cirrus sockets separated interradially by narrow flat strip or weak interradial ridges, except in S. varians , which has more conspicuous, sinuous interradial ridges extending to the tip of the centrodorsal. Cirrus sockets with fulcral bowls surrounding central lumen; socket margins finely crenulate. Distal cirrals wider than long. Row of spines present on proximal brachials. First segment of P 1 with L/W = 1.1–1.8. Angle between the lateral edge of IBr 1 and the oral/aboral axis largely obtuse.

Type species: Zenometra triserialis A.H. Clark, 1908 ( Fig. 6F).

Sarametra varians sp. nov. ( Figs 7–10) ZooBankregistration: urn:lsid:zoobank.org:act:.

Diagnosis: Centrodorsal conical or truncated conical, taller than wide ( H/D = 1.2–1.3), with two or three columns of cirrus sockets in each radial area. Cirrus sockets are separated interradially by weak to moderately developed interradial ridges, usually sinuous and extend to the aboral pole. Proximal brachials with conspicuous synarthrial and articular tubercles. Sparse and short spines on proximal brachials. P 1 6.7–10.0 mm, 13–15 pinnulars. The first pinnular of P

1

with L/W = 1.5–1.7.

Material examined: Holotype (RSIOCRI0292), Northwest Pacific, 12.5365°N, 149.6961°E, depth 2922 m, 26 July 2023, collected by HOV Jiaolong. Paratypes: RSIOCRI0007, Northwest Pacific, 15.9769°N, 155.2828°E, depth 2743m, 23 July 2014, collected by HOV Jiaolong; RSIOCRI0207, Northwest Pacific, 25.4525°N, 149.4811°E, depth 2749 m, 25 June 2023, collected by HOV Jiaolong; RSIOCRI0291, Northwest Pacific, 12.5365°N, 149.6961°E, depth 2922 m, 26 July 2023, collected by HOV Jiaolong. Other specimens: RSIOCRI0067 (broken arms only), Northwest Pacific, 15.4665°N, 161.7706°E, depth 2498 m, 21 September 2019, collected by ROV Hailong III.

Description of holotype RSIOCRI0292: Centrodorsal truncated conical and taller than wide ( H = 5.1 mm, D = 3.9 mm, H/D = 1.3) ( Fig. 8A). Cirrus sockets are separated interradially by elevated and sinuous interradial ridges that extends to the aboral pole. Aboral pole of centrodorsal excavated ( Fig. 8B). Tegmen naked, domed, with mouth central or subcentral. Surface of tegmen level at IIBr 4–5 ( Fig. 8D). Edge of lateral margins of radial articular facets visible interradially.

Cirri LII (functional sockets) in two or three columns per radial area. Each column with 4–6 functional sockets. There are very few obsolete sockets, only 1 or 2 per radial area. Fulcral bowl of cirrus sockets surrounding central lumen. Marginal crenulations of cirrus sockets fine. Cirri of 51–62 segments, 20–35 mm long. Longest cirral L/W = 2.0–2.5. Proximal cirrals cylindrical with distinctly concave aboral margins. c 1–4 very short. Cirrals increase in length from c 5 to c 10 ( Fig. 8G). Cirrals at distal fourth of the cirrus shorter than wide. Terminal claw curved beyond aboral margin of penultimate cirral. Few cirri with opposing spine.

Basals visible externally in each interradial. Radials short, without spines. Arms 10. IBr 1 short, W/L = 2.7 (2.7/1.0 mm). The distal edge of IBr 1 is prominent at straight angles to the axillary (IBr 2). Distal margin broadly V-shaped, longer than the proximal margin. Axillary (IBr 2) rhombic, W/L= 1.3 (3.3/ 2.6 mm). The proximolateral and distal margins are slightly concave. The dorsal surfaces of IBr 1 and IBr 2 are very high and arched with conspicuous synarthrial tubercles ( Fig. 8A, white arrow). IIBr 1 short, distal margin V-shaped, longer than proximal margin. W/L = 2.2 (2.0/ 0.9 mm). IIBr 2 cuneate, W = 1.6–2.2 mm, L = 1.6–1.8 mm, W/L = 1.0–1.3. First syzygy at IIBr 3+4, W = 1.9 mm. IIBr 5–8 square-shaped, W/L = 1.2–1.3. Second syzygy at IIBr 9 + 10, rectangle-shaped, W = 2.1 mm. Second syzygy occasionally at IIBr 10 + 11 or IIBr 12 +13. Subsequent interval 2–8. Proximal brachials equipped with sparse and short spines. From IIBr 5 onwards, brachials are smooth on the proximal margin, with fewer spines distally. Middle brachials cuneate or triangular, W/L = 1–1.2. Distal spines alternating on successive brachials. Distal brachials W/L = 0.9–1.2 ( Fig. 8F). Distal brachials cuneate in shape and much slender as arm narrows nearer tip.

Pinnules 10.0–14.0 mm in length, each with 9–20 pinnulars. Pinnular length 0.6–1.2mm. Proximal pinnulars compressed, following pinnulars gradually narrower, becoming extremely slender to tip. P 1 10 mm in length, with 15 segments. First pinnular L/W = 1.5 ( Fig. 8E). Middle pinnular of P 1 L/W = 1.8–3. Distal pinnular of P 1 L/W = 3. P 2 8.9–12.0 mm with 11–13 pinnulars. First genital pinnule P 4. P 4 flat and thin, the length of which is about 7.5mm, genitals not conspicuous. The following pinnules have a broad base, with short first pinnular and extremely slender distal pinnulars ( Fig.8F). The distal pinnules is about 14 mm long. P a 7.0– 8.7 mm, 11–13 pinnulars.The distal pinnules composed of oval-shaped and notably large pinnulars ( Fig. 8C, white arrow).

Description of paratypes: RSIOCRI0007 ( Fig. 9A–C), centrodorsal H = 4.1 mm, D = 3.1 mm, H/D = 1.3. Aboral pole of centrodorsal is convex. Interradial ridges slightly developed. Cirri XLVII (functional sockets). Functional cirrus sockets in two columns per radial area. Obsolete sockets 0–2 per radial area. 20–38mm long, with 38–60 segments. Longest cirral L/W = 2.4. c 1–4 very short. Cirrals increase in length from c 5 to c 8. IBr 1 short, W/L = 2.7 (2.5/ 0.9 mm). The distal edge of IBr 1 is prominent at straight angles to the axillary (IBr 2). Distal margin broadly V-shaped, longer than the proximal margin. Axillary (IBr 2) rhombic, W/L = 1.1 (3.2/3.0 mm). The proximolateral and distal margins are slightly concave.IIBr 1 short, distal margin V-shaped, longer than proximal margin. W/L = 2.4. IIBr 2 cuneate. W/L = 1.0 (1.6/ 1.6 mm). First syzygy at IIBr 3+ 4, W = 1.9 mm. Second syzygy at IIBr 9 +10, rectangle-shaped, W = 1.5 mm. IIBr 5–8 square-shaped, W/L = 1.1–1.2. Pinnules 7.0–15.0 mm in length, with 11–16 pinnulars. Pinnular length 0.6–1.1 mm. P 1 8.5 mm, 14 pinnulars. First pinnular L/W = 1.7. P 2 8.4 mm, 13 pinnulars. P a 7.0 mm, 12 pinnulars.

RSIOCRI0207 ( Fig. 9E, G), centrodorsal half-broken, H = 5.3 mm, D = 4.4 mm, H/D = 1.2. Centrodorsal is completely hollow. Cirri XLVII (functional sockets).Functional cirrus sockets in two columns per radial area, separated by elevated interradial ridges extending to the aboral pole. Cirri of 60–71 segments. Longest cirral L/W = 2. IBr 1 short, W/L = 4.0 (2.9/ 0.7 mm). The distal edge of IBr 1 is prominent at straight angles to the axillary (IBr 2). Distal margin broadly V-shaped, longer than the proximal margin. Axillary (IBr 2) rhombic, W/L = 1.1 (2.6/ 2.2 mm). The proximolateral and distal margins are slightly concave. IIBr 1 short, distal margin V-shaped, longer than proximal margin. W/L = 1.9. IIBr 2 cuneate. W/L = 1.1 (1.9/ 1.8 mm). First syzygy at IIBr 3 + 4, W = 1.7 mm. Second syzygy at IIBr 9 + 10, rectangle-shaped, W = 1.8 mm. IIBr 5-8 square-shaped, W/L = 1.1–1.3. Pinnule length 8.0– 12.5 mm, each with 9–18 pinnulars. P 1 8.0 mm in length, with 13 pinnulars. First pinnular L/W = 1.7. P 2 7.3 mm with 13 pinnulars. P a 7.0 mm, 13 pinnulars.

RSIOCRI0291 ( Fig. 9D, F), centrodorsal H = 5.3 mm D = 4.1 mm, H/D = 1.3. Aboral pole of centrodorsal excavated. Cirrus sockets are separated interradially by elevated, sinuous interradial ridges that extends to the aboral pole. Cirri LV (functional sockets). Functional cirrus sockets in two or three columns per radial area. Obsolete sockets 1–4 per radial area. Cirri 20–45 mm long, with 49–70 segments. Longest cirral L/W = 2.5. c 1–4 very short. Cirrals increase in length from c 5 to c 10. IBr 1 short, W/L =2.6 (2.6/1.0 mm).The distal edge of IBr 1 isprominent at straight angles to the axillary (IBr 2). Distal margin broadly V-shaped, longer than the proximal margin. Axillary (IBr 2) rhombic, W/L = 1.3. The proximolateral and distal margins are slightly concave. IIBr 1 short, distal margin V-shaped, longer than proximal margin. W/L = 2.5. IIBr 2 cuneate. W/L = 1.3 (2.2/ 1.7 mm). First syzygy at IIBr 3 +4, W = 1.7 mm. Second syzygy at IIBr 9 + 10, rectangle-shaped, W = 1.3 mm. IIBr 5-8 square-shaped, W/L = 1.2–1.4. Pinnule length 8.0– 17.6 mm, each with 10–20 pinnulars. P 1 9.5 mm in length, with 13 pinnulars. First pinnular L/W = 1.5. P

2

8.5 mm with 11 pinnulars. P

a

8.7 mm, 11 pinnulars.

Ossicle morphology: Paratypes RSIOCRI0291, RSIOCRI0007, and RSIOCRI0207 were partially dissected for ossicle observation. Cirrus sockets are well separated by the sinuous interradial ridges ( Fig. 10A). The proximal portion of the interradial ridges, where the basals are attached, exhibits a deep groove in both paratypes ( Fig. 10A, white arrow). Socket margins finely crenulate; concave fulcral stereom restricted to central bowl surrounding socket lumen ( Fig. 10A, B). The aboral pole shows a pentagonal-shaped regenerating skeleton with thin stereom ( Fig. 10C). The five radials attached closely with the basals ( Fig. 10D). Interradial processes of basal is broad, about as long as wide. The stereom on the inner side corresponds to a portion of the rosette ( Fig. 10E). The articular facet of each radial to the first brachial bears five fossae, including a pair of adoral muscle fossae (mf), a pair of interarticular ligament fossae (il), and an aboral ligament fossae (al). Narrow ridges separate the two adoral muscle fossae and two interarticular ligament fossae. Aboral to the fulcral ridge is the unpaired aboral ligament fossa which houses the extensor ligament bundle ( Hays 2016). IBr 1 W = 2.6 mm ( Fig. 10F). Axillary (IBr 2) rhombic bears two articular faces distally, with thin marginal spines. W = 3.3 mm, L = 2.6 mm, W/L = 1.3 ( Fig. 10G, H). IIBr 1 W = 2.8 mm ( Fig. 10I). IIBr 2 with short and inconspicuous spines ( Fig. 10J). First syzygy at IIBr 3+ 4. The syzygial articular surface of IIBr 3 oval shaped, with alternating radial ridges and depressions ( Fig. 10K).

Colour: Purple brown coloured ( Fig. 7A–C).

Etymology: The specific epithet ‘ varians ’ is a Latin adjective meaning ‘changing’ or ‘variable’, alluding to the morphological variability observed within this species, particularly in the shape of the centrodorsal and development of the interradial ridges.

Distribution: Known from RC seamount, Nazuna (HNN) seamount, RF seamount, Caiwei seamount, Northwest Pacific. Depth range 2498–2922 m. Attached to remnant coral stalk (RSIOCRI0291, RSIOCRI0292) or Primnoidae coral (RSIOCRI0207).

Remarks: The holotype RSIOCRI0292, and paratypes RSIOCRI0207 and RSIOCRI0291 demonstrated morphological similarities to the genus Zenometra , particularly in possessing a ‘cylindrical’ centrodorsal and elevated interradial ridges. However, molecular evidence suggests a close relationship of these specimens with Sarametra species ( Fig. 2). Paratype RSIOCRI0007, on the other hand, presents traits that occurs in typical Sarametra , such as having a conical centrodorsal and less developed interradial ridges. With intraspecific COI distances less than 0.4% ( Table 4), the polymorphism found in S. varians challenged the validity of the cylindrical centrodorsal and interradial ridge in defining genera, as noted in the assessment of generic diagnostic characters. Whether the observed similarity between S.varians and Zenometra columnaris suggests a close phylogenetic relationship is unknown as no DNA data of Z. columnaris is currently available.

In spite of the intraspecific variations, all specimens of S. varians share the same characters, in particular short and sparse spines on the proximal brachials, conspicuous synathrial and articular tubercles, as well as characters that fit with the genus, such as distal cirrals wider than long, first pinnular of P 1 less than twice as long as wide. It is attributed to Sarametra based on the current molecular and morphological evidence.The differences between S. varians and its congeners are listed in Table 6.