Rhynchothorax sidereus, Sabroux & Hassanin & Corbari, 2022

Sabroux, Romain, Hassanin, Alexandre & Corbari, Laure, 2022, Sea spiders (Arthropoda: Pycnogonida) collected during the Madibenthos Expedition from Martinique shallow waters, European Journal of Taxonomy 851 (1), pp. 1-141 : 114-116

Rhynchothorax sidereus sp. nov.

urn:lsid:zoobank.org:act:DF2C9474-DD03-4190-A39F-37F9F8E43435

Fig. 31

Rhynchothorax sp. 1 – Sabroux et al. 2019b: tab. 1, fig. 3.

Material examined

Holotype MARTINIQUE • 1 subadult?; Canal de Ste Lucie ; 14°22.7ʹ N, 60°51.6ʹ W; depth 65 m; 11 Sep. 2016; st. AD222; MNHN-IU-2016-817/ MK411138 .

Etymology

From the Latin ‘ sidereus ’, - a, - um (adj.), ‘starry’, in memory of long working nights sorting samples and of the nice starry sky above. The name also refers to the many tubercular projections of the specimen, which gives it a meteor-like shape.

Description (holotype, MNHN-IU-2016-817)

BODY. Trunk and legs cuticle granulated, incompletely segmented with 3 rd and 4 th segments fused. 1 st to 3 rd segments with mediodorsal conical granulose tubercle near posterior margin. Ocular tubercle grossly club-shaped, slender at base, leaning forward, with 4 large pigmented eyes, ornamented with 3 cones above eyes, one slender anterolateral pair corresponding to lateral sense organs plus single cone on dorsomedian surface. Cephalon ornamented with 2 tall, slender, conical tubercles situated posterior to ocular tubercle base. Lateral projections of cephalon (on which palps articulate) conspicuously diverging from cephalic segment, anteriorly directed. Lateral processes of 1 st, 2 nd and 3 rd segments as long as wide, all well separated by less than half their diameter at base; lateral processes on 4 th segment shorter than wide, touching 3 rd pair at base. All lateral processes unornamented.

PROBOScIS. Surface smooth, reaching 3 rd palp article, without conspicuous dorsomedian tubercle, with 2 pairs of dorsolateral bulges at about mid-length and ⅔ of proboscis length, latter most conspicous. Distal part down-curved. Lips bilateral, vertical, with inner and outer antimeres.

ABDOMEN. Horizontal, cylindrical, blunt, about 3 times as long as wide, extending lightly beyond coxae 2. No basal segmentation.

CHELIFORE. Absent.

PALP. 5-articled. 1 st article shorter than wide, with inconspicuous articulation. 2 nd article longest, about 7 times as long as wide, with dorsal tubercle at distal end, tip with spine. 3 rd article about 0.6 times as long as 2 nd and 4 times as long as 4 th, carrying scarce setae, with large spine on inner side distally. 4 th article about as long as wide, carrying many setae. 5 th article shortest, bud-like, carrying many setae.

OvIGER. 10-articled. 1 st article about as long as wide, glabrous. 2 nd article slightly longer than 1 st, more than 1.5 times as long as wide, glabrous. 3 rd article slightly longer than 2 nd, about 4/3 times as long as wide, glabrous. 4 th article longest, about 2.5 times as long as 3 rd and 5 times as long as wide, with distal seta. 5 th article half as long as 4 th and more than 1.5 times as long as wide, curved, carrying distal seta. 6 th article about 0.9 times as long as 4 th and about 3 times as long as wide, carrying proximal seta. 7 th article about 4/3 times as long as wide. 8 th and 9 th articles subequal, about as long as wide. 10 th article larger, rounded, about as long as wide, typical of the genus in having lamina on inner strigilis surface in addition to strigilis spine and terminal claw. Striglis typical, formula 3:3:3:2, with bifurcated spine on each article. Terminal claw inner surface apparently flattened, about as long as strigilis lamina.

LEGS. Slender. Coxa 1 bearing one dorsomedian and 2 lateral granulated projections on 1 st, 2 nd and 3 rd legs, only one anterior projection on 4 th leg. Coxa 2 of about same size, slenderer, unornamented. Coxa 3 small, unornamented. Femur approximately 4 times as long as wide. Tibiae 1 and 2 slenderer than femur, bearing long dorsomedian spine at distal end. Tibia 1 of about same size as femur, tibia 2 slightly shorter than femur or tibia 1. Tarsus medium-sized. Propodus about ⅙ shorter than tibia 2, setose, sole gently curved, bearing 4 spines. Main claw about half as long as propodus. No auxiliary claw. Gonopores inconspicuous.

MEASUREMENTS (mm). Trunk 0.47; abdomen 0.16; proboscis 0.31; palp 0.33; coxa 1 0.07; coxa 2 0.07; coxa 3 0.06; femur 0.24; tibia 1 0.22; tibia 2 0.19; tarsus 0.04; propodus 0.18; main claw 0.08.

Remarks

Rhynchothorax sidereus sp. nov. is distinguished from most other species of the genus by the following combination of characters: presence of pigmented eyes; presence of one dorsodistal spur on second palp article; two conical tubercles posterior to ocular tubercle base; three tubercles on coxa 1 of first, second and third legs; no ornamentation on lateral processes. These characters are shared with R. orientalis Child, 1988 from Philippines. Rhynchothorax sidereus sp. nov. differs from Child’s (1988a) specimen in showing no bifid extremity of the dorsomedian tubercles or any anterior projection of the ocular tubercle. The species R. sidereus is also morphologically similar to R. swir Staples, 2019 from the southwest Indian Ridge, but the former has distinctive tall tubercles on the ocular tubercle and is without conical tubercles on the lateral processes ( Staples 2019).

Distribution

Only known from type locality.

Depth range

65 m.

Figures

Fig. 31. Rhynchothorax sidereus sp. nov., holotype, MNHN-IU-2016-817. A. Body, dorsal view. B. Body, lateral view (same scale as A). C. Palp terminal segments, ventral view.D. Third leg. E. Oviger.