Nilgirius pygoprominulus Zhao & Zhang, 2023

Zhao, Jingjing, Cheng, Zien & Zhang, Chao, 2023, Description of Nilgirius pygoprominulus sp. n. (Opiliones, Assamiidae, Trionyxellinae) from China, with notes on its sexual dimorphism, Biodiversity Data Journal 11, pp. 102954-102954 : 102954

Nilgirius pygoprominulus Zhao & Zhang sp. n.

Materials

Type status: Holotype. Occurrence: individualID: MHBU-Opi-17ZC 1101m; individualCount: 1; sex: male; lifeStage: adult; occurrenceID: 5C7FD976-0913-5430-9604-D0E35898A1BD; Taxon: scientificName: Nilgirius pygoprominulus; class: Arachnida ; order: Opiliones ; family: Assamiidae ; Location : country: China; countryCode: CHN; stateProvince: Yunnan; municipality: Baoshan ; locality: Lujiang Town ; verbatimElevation: 164m; decimalLatitude: 24.947778; decimalLongitude: 98.832778; Identification : identifiedBy: Chi Jin ; Event : samplingProtocol: by hand; year: 2017; month: 5; day: 29; Record Level : institutionID: the Museum of Hebei University ; institutionCode: MHBU Type status: Paratype. Occurrence: individualID: MHBU-Opi-17ZC1101f-1103f; individualCount: 3; sex: female; lifeStage: adult; occurrenceID: 9C77CD26-48D7-57B1-8571-3E7A693E74A8; Taxon: scientificName: Nilgirius pygoprominulus; class: Arachnida ; order: Opiliones ; family: Assamiidae ; Location : country: China; countryCode: CHN; stateProvince: Yunnan Province; municipality: Baoshan ; locality: Lujiang Town ; verbatimElevation: 164m; decimalLatitude: 24.947778; decimalLongitude: 98.832778; Identification : identifiedBy: Chi Jin ; Event : samplingProtocol: by hand; year: 2017; month: 5; day: 29; Record Level : institutionID: the Museum of Hebei University ; institutionCode: MHBU

Description

Male holotype. Habitus as presented in Fig. 2 A, C, Fig. 3 A and Fig. 5 A-C. Colouration in ethanol: entire body dorsally rusty yellow with dark brown patches; median area of prosoma with dark brown reticulations before and behind the interocular mound; both lateral ridges of scutum with dark brown stripes; dorsal scutal areas I-V and free tergites dark brown with transverse paler interspaces. Coxae with light brown patches on edges and surface. Chelicerae, pedipalpi and legs reticulated with light to dark brown.

Dorsum (Fig. 2 A; Fig. 5 A). Dorsal scutum (DS) pyriform, with the widest portion at scutal area II, as a typical beta shape（Fig. 2 A; Fig. 5 A). Mid-bulge symmetrical, centred around mid-DS, covering two-thirds of scutum length. Carapace narrower than mid-bulge, subparallel, widening posteriorly. Posterior border of scutum moderately convex, narrower than mid-bulge. Anterior margin of carapace with two spines at the lateral portion and a single median spine, all similar spines directed horizontally, the middle one is the smallest. Interocular mound oval and armed with a spine median longer than the height of interocular mound (Fig. 3 A, lateral view). Scutal areas I-V each with a row of acuminate tubercles and a longitudinal row of similar tubercles on the lateral margins. Free tergites and anal operculum also armed with a row of tubercles that are more slender and dapper than scutal areas I-V.

Venter (Fig. 2 C; Fig. 5 C). Genital operculum and free sternites with hair-tipped granules. Spiracles concealed. Coxa I-IV with a row of marginal tubercles at the border and tuberculated on the ventral surface. Coxa IV enlarged.

Chelicerae (Fig. 2 G; Fig. 3 B-D). Basichelicerite elongate, with distinct bulla, no prominent armaments, except five small tubercles. Movable finger with twelve mound-shaped teeth; fixed finger with six teeth.

Pedipalpi (Fig. 3 E and F). Trochanter ventrally with an enlarged setiferous tubercle and a small one. Femur dorsally with a row of six small setiferous tubercles, ventrally with a row of six setiferous tubercles; meso-apically with one setiferous tubercle. Patella ventro-mesally with three and ventro-ectally with one tubercle. Tibia ventro-mesally with five and ventro-ectally with an enlarged tubercle and three small tubercles. Tarsus ventro-mesally and ventro-ectally each with six setiferous tubercles and tarsal claw slightly curved, shorter than tarsus.

Legs (Fig. 2 E; Fig. 6 A and B). All segments rounded in cross section, with scattered small tubercles. Femora III-IV slightly curved, distitarsi I with two tarsomeres and distitarsi II-IV with three tarsomeres. Tarsi III-IV each with a pseudonychium (Fig. 2 E; Fig. 6 A and B) and two bare claws. Tarsal formula (I-IV): 5(2)/10(3)/6(3)/7(3).

Penis (Fig. 4 A-E). Truncus (pars basalis) without muscle and tendon system, slender, sides nearly parallel, then slightly enlarged (Fig. 4 A, ventral view) and curved (Fig. 4 B and C, lateral view) towards distal end. Distal portion of penis (pars distalis) markedly enlarged: ventral plate nearly triangle and frontal rim with median crevice (Fig. 4 A, ventral view), convex in dorsal view and concave in ventral view (Fig. 4 B and C, lateral view); basal section mainly with two rounded lobes, convex in ventral view (Fig. 4 A and D, ventral and dorsal view). Glans composed of two-thirds of prickly funnel near the base and one-third of stylus and lamella (Fig. 4 B and C, lateral view). The distal portion of truncus (pars distalis) with 18 macrosetae distributed symmetrically. Five pairs of macrosetae inserted in both sides of ventral plate, the distal C1-C2 form a vertical line comparatively with the transversal A1-A3 proximally. Three pairs of macrosetae ventrally close to the centre of distal section (Fig. 4 A), one pair of proximal B proximally and two pairs of E1-E2 distally. One pair of D near the basal glans.

Female (Fig. 2 B, D, F and H; Fig. 4 F and G; Fig. 5 D-F; Fig. 6 C and D). Similar in colouration to male. Body size smaller than male. Scutum approximately trapezoidal. Legs and pedipalpi much shorter and thinner than those of male (Tables 1 , 2 ). Pseudonychium of legs III-IV in female reduced compared to that of male (Fig. 2 E and F; Fig. 6 ). Tarsal formula (I-IV): 5(2)/9(3)/6(3)/7(3). Movable finger of chelicera with eleven round teeth in female.

Ovipositor (Fig. 4 F and G). Short. Ventral surface with four setae and dorsal surface with six setae.

Sexual dimorphism. (1) body of male much larger than that of females; (2) dorsal scutum slightly piriform in male and approximately trapezoidal in females; (3) coxa of leg IV and pseudonychia of leg III-IV enlarged in male; (4) male leg IV much longer than female’s; (5) teeth on cheliceral finger in male a bit more robust than those of females.

Measurements. Male holotype (female paratype): Body 4.66 (3.35) long, 2.74 (2.09) wide at the widest portion. Scutum 3.65 (2.49) long. Interocular mound 0.40 (0.39）long, 0.26 (0.25) wide, 0.19 (0.18) high, 0.18 (0.15) far from the anterior border of the scutum. Pedipalpal claw 0.32 (0.26) long. Measurements of left pedipalpus and legs as in Tables 1 , 2 .

Diagnosis

The distal portion of male genital truncus (pars distalis) markedly enlarged and with two rounded lobes (Fig. 4 A). Penial macroseate A clustered transversally on the lateral vetral plate (Fig. 4 B). Dorsal scutum of male outline of type beta (Fig. 2 A; Fig. 5 A). Scutal areas I-V with scattered tubercles, free tergites each with transverse rows of acuminate tubercles. Interocular mound with one single large spine (Fig. 3 A; Fig. 5 B and E). Pedipalpal femur meso-apically with a setiferous tubercle and tibia ventro-ectally with an enlarged tubercle and three small tubercles (Fig. 3 E and F).

Etymology

The specific epithet combines the Greek word pyge, meaning "rump, buttocks", plus the Latin adjective prominulus, meaning "tubercle" or "spine". Pyge refers to the shape of penis and prominulus refers to the tubercle of the dorsal scutumn and legs of the new species.

Distribution

Known only from the type locality.

Figures

Figure 2. Nilgirius pygoprominulus sp. n., male holotype and female paratype (MHBU-Opi- 17 ZC 1101 f). A Male body, dorsal view; B Female body, dorsal view; C Male body, ventral view; D Female body, ventral view; E Right tarsal claw IV of male, lateral view; F Right tarsal claw IV of female, lateral view; G Cheliceral fingers of male, frontal view; H Cheliceral fingers of female, frontal view. Scale bars: 1 mm (A-D); 0.5 mm (E, F); 0.25 mm (G, H).

Figure 3. Nilgirius pygoprominulus sp. n., male holotype. A Male body, lateral view; B Left chelicera of male, ental view; C Same, ectal view; D Left cheliceral fingers, frontal view; E Left pedipalp of male, ental view; F Left pedipalp of male, ectal view; G Left pedipalp of male, dorsal view. Scale bars: 1 mm (A); 0.5 mm (B, C, E-G); 0.25 mm (D).

Figure 4. Nilgirius pygoprominulus sp. n., genitalia of male holotype and female paratype (MHBU-Opi- 17 ZC 1101 f). A Penis, ventral view; B Distal part of penis, lateral view; C Expanded, same; D Distal part of penis, dorsal view; E Expanded, same; F Ovipositor, dorsal view; G Same, ventral view. Scale bars: 0.25 mm.

Figure 5. Photographs of male (A-C, holotype) and female (D-F, paratype, MHBU-Opi- 17 ZC 1101 f) of Nilgirius pygoprominulus sp. n .. A Male body and parts of appendages, dorsal view; B Same, lateral view; C Same, ventral view; D Female body and parts of appendages, dorsal view; E Same, lateral view; F Same, ventral view. Scale bars: 1 mm.

Figure 6. Photographs of pseudonychium of leg III-IV in male holotype and female paratype (MHBU-Opi- 17 ZC 1101 f). A-B Pseudonychium of leg III-IV in male (holotype); C-D Pseudonychium of leg III-IV in female paratype (MHBU-Opi- 17 ZC 1101 f). Scale bars: 0.25 mm.