Sinonychia, 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

Sinonychia gen. n.

Figs 1–31 , 33

ZooBank LSID: urn:lsid:zoobank.org:act:3E5B75D9-94F0-4B4E-8D09-89A5A916495C

Type species: Sinonychia martensi sp. n.

Diagnosis. Sinonychia gen. n. can be differentiated from all other Cladonychiidae genera on the basis of penis morphology, having a combination of two pairs of relatively thick lateral setae on the glans, a cylindrical, basally widening glans, and an elongate stylus arising apically. Morphologically the new genus is most similar to Speleonychia from the Pacific Northwest of North America but can be distinguished by several characters. First, in spination of the penis: in Sinonychia gen. n. two pairs of apical setae on the penis are thick and at a 90˚ or larger angle to the stylus, whereas in Speleonychia these setae are at a much smaller angle, directed apicad ( Briggs 1974: figs 7–8). Second, the shape of the glans: in Sinonychia gen. n. the glans is almost cylindrical, with a wide, blunt apex and with the stylus arising sub-terminally, while in Speleonychia the glans is more triangular, with a more pointed apex and a stylus arising terminally. Third, in spination of the pedipalpal femur: Sinonychia gen. n. has multiple distal SBTs on the ventral surface at the distal end ( Figs 5–6 ), while Speleonychia has only a single SBT ( Briggs 1974: fig. 2).

Etymology. The generic name is composed of “Sino”, derived from the Latin word “Sinae” (from the Ancient Greek “Σῖναι”) which generally refers to China, and of the Latin noun “onyx” (from the Ancient Greek “ὄνῠχος”) meaning ‘claw’, a common name applied to many travunioid and triaenonychoid genera. The second part of the new genus name also indicates morphological similarity with the genus Speleonychia . The genus name is feminine.

Description. Highly troglomorphic with unpigmented body ( Figs 22–31 ). Ocularium greatly reduced in size, smooth, set back from anterior margin of carapace; eyes and retinae completely absent ( Figs 1 , 22–31 ). Dorsal scutum of the “eta” (η) category of Kury & Medrano (2016). Genital operculum nearly triangular ( Fig. 9 ). Sternum elongate and narrowly triangular ( Fig. 8 ). Pedipalps thin, elongate, lacking pigment, with thin SBTs ( Figs 5–6 ). Legs extremely long, thin, and lacking pigment. Claws III–IV with peltonychium ( Figs 10–13 ). Penis truncus thin and elongate, musculature restricted to its base ( Fig. 16 ); glans articulated with truncus, with two pairs of setae, the more distal pair being smaller than the other pair; stylus elongate, arising apically from glans ( Figs 17–19 ).

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.