Sinonychia martensi, Zhang & Derkarabetian, 2021

Zhang, Chao & Derkarabetian, Shahan, 2021, First record of Travunioidea (Arachnida: Opiliones: Laniatores) from China, with the description of a new monotypic genus from a cave, Zootaxa 4984 (1), pp. 87-97 : 88-93

Sinonychia martensi sp. n.

Figs 1–31 , 33

ZooBank LSID: urn:lsid:zoobank.org:act:1FD58240-64B2-4B4B-8679-718B8A65FAFB

Type material. CHINA: Beijing: Holotype male (MHBU-Opi-18 ZC0604 ), Beijing City, Fangshan District, Beiyao Village , Tangren Cave , N 39°47’, E 115°52’, 70 m elevation, leg. Z.G. Feng 12.9.2018 . Paratypes: 1 female allotype (MHBU-Opi-18 ZC0605 ) , 14 females (MHBU-Opi-18 ZC0606–0619 ) with collecting data as for holotype except: leg. Z.Y. Li. 12 females (MHBU-Opi-20 ZC1201–1212 ) with collecting data as for holotype except: leg. C. Zhang, X.H. Ru & Q.W. Cui 20.12.2020 .

Diagnosis. As given for the genus.

Etymology. The new species is dedicated to Prof. Dr Jochen Martens (Mainz, Germany), one of the top ten opilionologists who have described the most species ( Machado et al. 2007); name in the genitive case.

Description. Male (holotype). Habitus as in Figs 1 , 7 , 22–24 . Colouration ( Figs 22–24 ): entire body pale yellow. Body length 1.92, scute length 1.54, scute width 1.15, carapace width 0.95, LII/SL 9.65.

Dorsum ( Figs 7 , 22 ). Scutum minutely granular, scutum outline of the “eta” (η) category; posterior region of scutum widest, posterior end of opisthosoma convex. Surface of carapace completely smooth, anterior margin unarmed. Ocularium low, slightly conical, unarmed, without eyes, set back from anterior margin of scutum by 0.08 mm. Grooves between scutal areas inconspicuous. Free tergites and anal operculum unarmed.

Venter ( Figs 8 , 24 ). Genital operculum nearly triangular ( Fig. 9 ). Coxae I–IV, genital operculum and free sternites finely granular and covered with scattered minute setae. Sternum elongate, narrowly triangular ( Fig. 8 ). Spiracles clearly visible.

Chelicerae ( Figs 2–4 ). Basichelicerite slender, without distinct dorso-distal bulla, no prominent armament except for three small SBTs. Cheliceral hand unarmed, pro-dorsally with SBTs, the inner ones larger than the outer ones, some SBTs ectally, ventrally, and entally in sub-distal portion. Fingers relatively short, inner edges dentate ( Fig. 4 ); movable finger with eight small, rounded teeth; fixed finger with five more distinctly pointed teeth.

Pedipalps ( Figs 5–6 ). Measurements given in Table 1 . Coxae dorsally unarmed and ventrally with one large and one small SBT ( Figs 6, 8 ). Trochanter dorsally with one very small SBT, ventrally with one large SBT and one small accessory SBT. Femur dorsally convex, with a row of reduced SBTs; ventrally with three enlarged SBTs basally, followed by three small SBTs, the most distal one of them located ectally, with two SBTs distally on ental side. Patella ventro-entally with two SBTs and ventro-ectally with one SBT. Tibia with three SBTs each ventro-entally and ventro-ectally. Tarsus ventro-entally with three and ventro-ectally with four SBTs. Tarsal claw 0.38 long, curved, shorter than tarsus.

Legs. All elongated; measurements given in Table 1 . All segments smooth, with only few short setae. Femur IV straight. Claws of legs III–IV developed as peltonychia with only one pair of distolateral prongs in both wings of the central shield and with pointed distal prong ( Figs 10–11 ). Distitarsus I with two, distitarsus II with seven tarsomeres. Distitarsi III–IV without scopula. Tarsal formula (I–IV): 7,17,4,4.

Penis ( Figs 16–19 ). Penis 1.31 long, truncus slender, nearly parallel-sided. Joint between glans and truncus articulated. Truncus distally and basally inflated; musculature limited to base of truncus. Glans almost cylindrical, longer than wide, distally contracted (in lateral view), basally slightly inflated. Distal portion of glans dorsally with weak invagination from where stylus arises, and laterally with two pairs of thick recurved setae. Apical pair of setae smaller than other pair and nearly perpendicular to axis of stylus; subapical pair of setae larger than apical pair and more strongly inclined towards base of penis. Stylus thin, cylindrical, and tubular.

Female ( Figs 12–15 , 20–21 , 25–31 , 33 ). In general appearance very similar to male. Allotype (MHBU-Opi- 18ZC0605): Body length 2.09, dorsal scute length 1.41, scute width 1.23, carapace width 0.85. Measurements of pedipalp and legs given in Table 1 . Pedipalpal claw length 0.40. Midgut ( Fig. 15 ) with triangular D1, elongate OD2 with two branches, and an elongate OD3 with two branches. Free ninth tergite and lateral sclerites present ( Fig. 14 ).

Ovipositor ( Figs 20–21 ). Four distal lobes. Ventral and dorsal lobes without setae. Each lateral lobe with two pairs of setae on lateral surface, without distal setae.

Variation. Size range of females (n = 27): body length 1.63–2.14, width 1.10–1.25. Colouration of the body varies from yellowish white to pale yellow ( Figs 28–31 ). The outline of the dorsum varies from trapezoidal ( Fig. 28 ) to elongate trapezoidal ( Figs 29–31 ). The distal portion and prongs of claws III–IV vary in their degree of fusion with the central shield ( Figs 12–13 ).

Notes. Sexual dimorphism is not exhibited in this species. Only a single male specimen was found among a total of 28 specimens. To avoid damage to the male holotype, some characters of the male that are not easily observable were only examined in the females. For example, the ninth tergite and lateral sclerites were observed by placing specimens into 10% KOH for a few minutes to dissolve the tissue ( Fig. 14 ), and midgut morphology was observed by dissecting specimens ( Fig. 15 ).

Distribution. Known only from the type locality.

Habitat. Tangren Cave lies in the Majiagou Formation of the Middle Ordovician, formed about 440–500 million years ago. The main body of the cave is deep in the mountain, 40 to 60 metres below the surface, with a northeast to southwest course. The temperature in the cave is 15–18℃ and the relative humidity is 95%. The cave entrance on the hillside ( Fig. 32 ) leads to a relatively narrow and small vertical shaft. The cave is divided into three sections. The first section is about 6 metres long, close to the cliff. The second section is about 39 metres long and vertical, nearly 30 metres of it requires a suspended descent. The third section is about 10 metres long and also requires a suspended descent. The Tangren cave extends downward along the limestone stratum in the southwest of the mountain, with a slope of 20–30 degrees. About 100 metres from the entrance there is a spacious hall, 3–20 metres high and 2–40 metres wide. All specimens were collected in this hall, most of them under stones by hand, a few on the cave walls. The cave was visited by the collectors twice.

Figures

FIGURES 1–5. Sinonychia martensi gen. n. & sp. n., holotype male (MHBU-Opi-18ZC0604). 1 Body, lateral. 2–3 Left chelicera (2 ental, 3 ectal). 4 Cheliceral fingers, frontal. 5 Left pedipalp, ectal. Scale bars: 1 mm (1, 5); 0.5 mm (2–3); 0.25 mm (4).

FIGURES 6–15. Sinonychia martensi gen. n. & sp. n., holotype male (6–11: MHBU-Opi-18ZC0604) and female paratypes (12–13: MHBU-Opi-18ZC0605, 14: MHBU-Opi-18ZC0616, 15: MHBU-Opi-20ZC1205). 6 Left pedipalp, ental. 7 Body, dorsal. 8 Sternum, leg coxae I–IV and palpal coxae (genital operculum removed). 9 Genital operculum. 10–11 Right tarsal claw IV (10 lateral, 11 dorsal). 12–13 Right tarsal claw III (12 lateral, 13 dorsal). 14 Opisthosoma, lateral. 15 Midgut, dorsal. Abbreviations: D1—first primary diverticula, OD2—opisthosomal diverticula 2, OD3—opisthosomal diverticula 3. Scale bars: 1 mm (6–7, 14); 0.5 mm (8, 15); 0.25 mm (9–13).

FIGURES 16–21. Sinonychia martensi gen. n. & sp. n., holotype male (16–19: MHBU-Opi-18ZC0604) and female paratype (20–21: MHBU-Opi-18ZC0605). 16 Penis, lateral. 17–19 Distal part of penis (17 ventral, 18 dorsal, 19 lateral). 20–21 Ovipositor (20 ventral, 21 dorsal). Scale bars: 0.5 mm (16); 0.25 mm (20–21); 0.125 mm (17–19).

FIGURES 22–27. Sinonychia martensi gen. n. & sp. n., male holotype (22–24: MHBU-Opi-18ZC0604) and female allotype (25–27: MHBU-Opi-18ZC0605), photographs of body and parts of appendages (22, 25 dorsal; 23, 26 lateral; 24, 27 ventral). Scale bars: 1 mm.

FIGURES 28–31. Sinonychia martensi gen. n. & sp. n., photographs of body and parts of appendages of four female paratypes (MHBU-Opi-18ZC0608–0611), dorsal. Scale bars: 0.5 mm (30); 1 mm (28–29); 2 mm (31).

FIGURES 32–33. Sinonychia martensi gen. n. & sp. n. and its type locality. 32. Entrance of Tangren Cave. 33. Living female (MHBU-Opi-20ZC1212) in its natural habitat.