Metachelifer thailandicus, Li & Shi, 2022

Li, Yun-Chun & Shi, Ai-Min, 2022, Cave-inhabiting Cheliferidae (Arachnida, Pseudoscorpiones) from Thailand, with description of four new species of Metachelifer Redikorzev, ZooKeys 1103, pp. 171-188 : 171

Metachelifer thailandicus sp. nov.

Figs 4 , 6C, D

Type material.

Holotype male: Thailand, Tak Province, Phop Phra district, Mae Ku subdistrict, Tham Sua Yai Cave, 16°40.336'N, 98°40.138'E, 466 m a.s.l., 14 Nov 2016, Yun-Chun Li and Zhi-Gang Chen leg., in MCWNU (Ms20161116-01). Paratypes: 1 male, 4 females, collected with the holotype in MCWNU (Ms20161116-01).

Diagnosis.

Troglobiont habitus. This new species is distinguished from other members of the genus Metachelifer by the following combination of characters: anterior margin of carapace with 6 denticuloclavate setae and a total of 86-88 setae; chelicera galea with 2 short branches; male movable chelal finger 0.96-0.98 × and female 0.93-0.95 × longer than hand with pedicel length; male anterior genital operculum without tubular setae; female genital posterior operculum with 6 setae, without lyrifissures.

Etymology.

Latinized adjective, derived from the country of Thailand, where the type locality is located.

Description.

Adult male (Fig. 6C ). Carapace and pedipalps dark brown, remaining parts yellowish brown (Fig. 6C ).

Carapace (Fig. 4A ): 1.06-1.07 × longer than broad, with a pair of well-developed eyes, length of eyes 0.10 mm, breadth 0.04 mm, carapace surface evenly and strongly granular. Median and posterior furrows prominent, regularly granular. Dorsal setae of carapace, borne on larger but relatively inconspicuous tubercles. With a total of 86-88 denticuloclavate setae, including 6 on anterior margin and 12-13 on posterior margin. Coxae: manducatory process with 4 setae (1 long apical, 1 rather short subapical seta, and 2 suboral setae at base of medial margin). Pedipalpal coxa with 11-12 (non-denticulate) + 7-8 (denticulate) setae, coxa I 9-11, II 13-15, III 15-18, IV with an anterolateral process and 39-45 setae. Coxal sac occupying only 2/5 of coxal length, atrium well developed (Fig. 4D ). Chelicera (Fig. 4B ): 1.90-1.91 × longer than broad, hand with 5 setae and 1 lyrifissure dorsally, movable finger with 1 submedial seta and 1-2 teeth (Fig. 4B ). Galea with 2 short branches. Serrula exterior with about 18-20 blades. Rallum with 3 blades, anterior one weakly denticulate distally. Pedipalp (Figs 4E-G ): all segments with well-developed granulations, except for chelal fingers, which are smooth; dorsal setae short and prominently denticuloclavate. Trochanter 2.00-2.03 × longer than broad, femur 6.13-6.15 × longer than broad, patella 4.74-4.77 × longer than broad, femur 1.15-1.16 × longer than patella. Chela with pedicel 5.50-5.53 × longer than broad, hand with pedicel 2.84-2.85 × longer than broad; movable finger 0.96-0.98 × longer than hand with pedicel length. Fixed finger with 59-61 small cusped teeth, movable finger with 58-61 teeth; venom apparatus present in both chelal fingers, very short (Fig. 4F ). Fixed chelal finger with 8 trichobothria and movable finger with 4, eb - esb (retrolateral view) and ib-isb (dorsal view) at the base of the fixed finger; est in finger middle, et distinctly closer to fingertip than to it; on movable finger, with one pseudotactile seta, nearer t, but the latter distinctly closer to fingertip, st nearer to sb than to t. Opisthosoma: tergal chaetotaxy (I-XI): 14: 13: 13: 17: 14: 15: 18: 13: 13: 13: 9; sternal chaetotaxy (IV-XI): 2 × 1 + 11: 12: 11: 10: 9: 11: 12: 9; anal cone with 2 dorsal and 2 ventral setae. Tergite XI with 2 tactile setae. Because only two specimens were available for the study, the structure of the genitalia could not be examined in detail. Anterior genital operculum with 74-78 setae (without tubular setae) and 2 lyrifissures; posterior operculum with 14-15 setae, 8-9 lyrifissures (Fig. 4H ). Legs: Leg I: surface weakly scale-like sculptured, trochanter 1.33-1.36 ×, femur 2.06-2.08 × longer than deep and 0.63-0.64 × longer than patella; patella 4.00-4.03 ×, tibia 4.67-4.69 ×, tarsus 5.00-5.02 × longer than deep, subterminal seta simple, claws modified and asymmetrical, lateral claw shorter than mesal one (Fig. 4C ). Leg IV: trochanter 1.94-1.95 ×, femoropatella 3.36-3.39 ×, tibia 7.50-7.53 × longer than deep and tarsus 6.67-6.71 × longer than deep. Arolia on legs I and IV shorter than claws (Fig. 4C ).

Adult female (Fig. 6D ). Mostly the same as the holotype. Carapace: Slightly longer than broad (1.01-1.02 ×), posterior margin with 8-9 setae. Well-developed paramedian impressions behind eyes like in male. Coxae: pedipalpal coxa with 11-13 (non-denticulate) + 5-6 (denticulate) setae, coxa I 11, II 15, III 23, IV 46. Chelicera: 1.80-1.86 × longer than broad, movable finger with 2 teeth. Pedipalp: trochanter 2.04-2.06 × longer than broad, femur 5.94-5.97 × longer than broad, patella 4.29-4.31 × longer than broad, femur 1.19-1.20 × longer than patella. Chela with pedicel 5.47-5.50 × longer than broad, hand with pedicel 2.87-2.89 × longer than broad; movable finger 0.93-0.95 × longer than hand with pedicel length. Opisthosoma: tergal chaetotaxy (I-XII): 10: 9: 11: 9: 10: 12: 11: 11: 12: 11: 10; sternal chaetotaxy (IV-XII): 2 × 1 + 9: 12: 13: 14: 13: 12: 11: 10; anal cone with 2 dorsal and 2 ventral setae. Anterior genital operculum with 18-20 setae (without tubular setae) and 1 lyrifissure; posterior operculum with 6 setae, without lyrifissures (Fig. 4I ). Sternites with 2 lateral cribriform plates.

Dimensions

(length/width or, in the case of the legs, length/depth in mm). Males (females in parentheses): body length 3.38-3.42 (2.86-3.32). Carapace 0.99-1.01/0.93-0.94 (0.81-0.82/0.80-0.81). Pedipalp: trochanter 0.60-0.62/0.30-0.31 (0.49-0.51/0.24-0.26), femur 1.47-1.49/0.24-0.25 (1.07-1.09/0.18-0.20), patella 1.28-1.30/0.27-0.28 (0.90-0.92/0.21-0.22), hand with pedicel 1.08-1.10/0.38-0.39 (0.86-0.89/0.30-0.32), length of movable chelal finger 1.04-1.06 (0.80-0.83), length of chela 2.09-2.11/0.38-0.39 (1.64-1.67/0.30-0.32). Chelicera: 0.27-0.28/0.14-0.15 (0.23-0.25/0.13-0.14). Leg I: trochanter 0.24-0.25/0.18-0.19 (0.18-0.20/0.14-0.16), femur 0.35-0.37/0.17-0.19 (0.21-0.23/0.14-0.15), patella 0.56-0.58/0.14-0.15 (0.46-0.49/0.13-0.14), tibia 0.56-0.58/0.12-0.13 (0.40-0.43/0.10-0.11), tarsus 0.50-0.51/0.10-0.11 (0.41-0.42/0.09-0.10). Leg IV: trochanter 0.33-0.34/0.17-0.19 (0.31-0.33/0.17-0.19), femoropatella 0.94-0.97/0.28-0.29 (0.72-0.75/0.22-0.23), tibia 0.90-0.93/0.12-0.13 (0.65-0.68/0.11-0.12), tarsus 0.60-0.61/0.09-0.10 (0.45-0.49/0.08-0.09).

Distribution.

Thailand (Tak).

Figures

Figure 4. Metachelifer thailandicus sp. nov., holotype male (A-H) and paratype female (I) A carapace B right chelicera C detail on tarsus I, lateral view D coxa IV, ventral view E palp (minus chela) F chela, retrolateral view G chela, dorsal view H male genital area I female genital area. Scale bars: 0.50 mm.

Figure 6. A, B Metachelifer takensis sp. nov., dorsal views A holotype male B paratype female C, D M. thailandicus sp. nov., dorsal views C holotype male D paratype female. Scale bar: 1.00 mm (A-D).