Tyrannochthonius gracilis, Hou & Feng & Zhang, 2023

Hou, Yanmeng, Feng, Zegang & Zhang, Feng, 2023, Diversity of cave-dwelling pseudoscorpions from Guizhou in China, with the description of twenty-four new species of the genus Tyrannochthonius (Pseudoscorpiones, Chthoniidae), Zootaxa 5262 (1), pp. 1-158 : 48-54

Tyrannochthonius gracilis sp. nov. ‹KḦƟṁae›

Figs 37–41

Type material. Holotype ♂ (Ps.- MHBU-HBUARA#2022-490-01 ): China, Guizhou Province, Hezhang County, Pingshan Town, Jiangnan Village , Xianren Cave , under stones, detritus and on the cave walls within 20–200 m from the cave entrance (Temperature: 14°C, Humidity: 85%) [27°7′51.46″N, 104°57′20.45″E], 1446 m a.s.l., 30 July 2022, Yanmeng Hou, Lu Zhang, Jianzhou Sun & Wenlong Fan leg. Paratypes: 13 ♂ (Ps.- MHBU-HBUARA#2022- 490-02 – HBUARA#2022-490-14 ) , 15 ♀ (Ps.- MHBU-HBUARA#2022-490-15 – HBUARA#2022-490-29 ), all with the same data as the holotype ; 4 ♂ (Ps.- MSWU- GZC190808-01 – GZC190808-04 ) , 8 ♀ (Ps.- MSWU- GZC190808- 05 – GZC190808-12 ), 8 August 2019, Zegang Feng, Zhaoyi Li & Chen Zhang leg., all with the same location as the holotype .

Etymology. The specific name is derived from the Latin word “ gracilis ”, meaning gracile, which refers to the elongated coxal spines.

Diagnosis (J ♀). Moderately sized troglomorphic species with elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated, epistome small and pointed, triangular; posterior margin of carapace with 2 setae; tergites I–IV each with 2 setae. Pedipalps slender, femur 8.50–8.88 (♂), 8.05–8.53 (♀) times longer than broad; chela 8.79–9.04 (♂), 8.41–8.81 (♀) times longer than broad; only fixed chelal finger with intercalary teeth.

Description. Males (holotype and paratypes) ( Figs 38A , 39A–F , 40 , 41 ).

Colour: generally pale yellow, chelicerae, pedipalps and tergites slightly darker, soft parts pale.

Cephalothorax ( Figs 39C , 40A ): carapace 0.99–1.00 times longer than broad, gently narrowed posteriorly; surface smooth, without furrows; no traces of eyes; anterior margin slightly serrate; epistome small and pointed, triangular, with 2 setae flanking base; with 18 setae arranged s4s: 4: 4: 2: 2, most setae heavy, long and gently curved, anterolateral setae much shorter than others; with two pairs of lyrifissures, first pair situated middle to the setae of ocular row, the second situated exter ior to the sole pair of setae of posterior row. Chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5; manducatory process with two acuminate distal setae, anterior seta less than 1/2 length of medial seta; apex of coxa I with small, rounded anteromedial process; coxae II with 11–12 terminally indented coxal spines on each side, set as an oblique and arc row, longer spines present in the middle of the row, becoming shorter distally and proximally and incised for about half their length ( Fig. 40C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 39D , 40B ): large, about as long as carapace, 2.50–2.53 times longer than broad; 5 setae and 2 lyrifissures (exterior condylar lyrifissure and exterior lyrifissure) present on hand, all setae acuminate, ventrobasal seta shorter than others; movable finger with one medial seta. Cheliceral palm with moderate hispid granulation on both ventral and dorsal sides. Both fingers well provided with teeth, fixed finger with 15–18 teeth, distal one largest; movable finger with 18–21 retrorse contiguous small teeth; galea completely vestigial ( Fig. 40B ). Serrula exterior with 21–22 and serrula interior with 14–15 blades. Rallum with 6 blades, the distal one longest and recumbent basally, with fine barbules and slightly set apart from the other blades, latter tightly grouped and with long pinnae, some of which are subdivided ( Fig. 40E ).

Pedipalp ( Figs 39A, B, E , 40D , 41A, B ): long and slender, trochanter 1.24–1.40, femur 8.50–8.88, patella 2.70–3.05, chela 8.79–9.04, hand 3.08–3.30 times longer than broad; femur 2.47–2.48 times longer than patella; movable chelal finger 1.63–1.76 times longer than hand and 0.60–0.62 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissure present on patella ( Figs 39E , 40D ). Chelal palm not constricted towards fingers, apodeme complex of movable chelal finger only slightly sclerotized, with weak granulation dorsally at base of fixed chelal finger. Fixed chelal finger and hand with 8 trichobothria, movable chelal finger with 4 trichobothria, ib and isb situated close together, submedially on dorsum of chelal hand; eb, esb and ist forming a nearly straight oblique row at base of fixed chelal finger; it slightly distal to est, situated subdistally; et slightly near to tip of fixed chelal finger, very close to chelal teeth; dx situated distal to et; sb closer to b than to st; b and t situated subdistally, t situated distal to b and slightly proximal to est ( Fig. 41A ). A tiny antiaxial lyrifissure present at base of fixed chelal finger (situated distal to ist). Both chelal fingers with a row of teeth, heterodentate, spaced regularly along the margin, larger and well-spaced teeth present in the middle of the row, becoming smaller and closer distally and proximally: fixed chelal finger with 28–30 macrodenticles, long and pointed, plus 14– 15 intercalary microdenticles, 42–45 in total; movable chelal finger with 34–37 macrodenticles (smaller than teeth on fixed chelal finger), slightly retrorse and pointed, plus 5–6 vestigial, rounded and contiguous basal teeth, 40–42 in total, without intercalary teeth ( Fig. 41A ). Chelal fingers straight in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs 39B , 41B ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 2: 2: 2: 2: 4: 4: 4: 4: 5: 4: T2T: 0; tergite IX with an unpaired median seta. Sternal chaetotaxy III–XII: 11–12: 10: 8: 7–8: 6–7: 7: 7: 7: 0: 2. Anterior genital operculum with 10–12 setae, genital opening slit-like, with 9–11 marginal setae on each side, 31–33 in total ( Fig. 39F ).

Legs ( Fig. 41C, D ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.76–1.77 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.37–2.41 times longer than tibia. Femoropatella of leg IV 3.93–4.41 times longer than deep; tibia 6.75–6.83 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 3.80–4.00 times longer than deep (TS= 0.23–0.26), tarsus 14.14–14.57 times longer than deep and 2.48–2.68 times longer than metatarsus (TS= 0.27). Arolium slightly shorter than the claws, not divided; claws simple.

Adult females (paratypes) ( Figs 37D , 38B , 39G ). Mostly same as males, but a little larger; chaetotaxy of coxae: P 3, I 3, II 3–4, III 5, IV 5; with same tergal chaetotaxy as males; sternal chaetotaxy IV–XII: 12–14: 8: 7–8: 7: 7: 7: 7: 0: 2; anterior genital operculum with 10 setae, posterior margin with 10–12 marginal setae, 20–22 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 4.56 times longer than deep (TS= 0.22–0.27), tarsus 13.25–14.57 times longer than deep and 2.49–2.59 times longer than metatarsus (TS= 0.21–0.26).

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 1.96–2.06. Pedipalps: trochanter 0.26–0.28/0.20–0.21 (1.24–1.40), femur 1.51–1.53/0.17–0.18 (8.50– 8.88), patella 0.61–0.62/0.20–0.23 (2.70–3.05), chela 2.08–2.11/0.23–0.24 (8.79–9.04), hand 0.74–0.76/0.23–0.24 (3.08–3.30), movable chelal finger length 1.24–1.30. Chelicera 0.80–0.86/0.32–0.34 (2.50–2.53), movable finger length 0.43–0.45. Carapace 0.68–0.71/0.68–0.72 (0.99–1.00). Leg I: trochanter 0.23/0.18–0.19 (1.21–1.28), femur 0.85–0.88/0.09–0.10 (8.80–9.44), patella 0.48–0.50/0.09 (5.33–5.56), tibia 0.38–0.39/0.06–0.08 (4.88–6.33), tarsus 0.90–0.94/0.06–0.07 (13.43–15.00). Leg IV: trochanter 0.32–0.33/0.18–0.20 (1.65–1.78), femoropatella 1.18–1.19/0.27–0.30 (3.93–4.41), tibia 0.81–0.82/0.12 (6.75–6.83), metatarsus 0.38–0.40/0.10 (3.80–4.00), tarsus 0.99–1.02/0.07 (14.14–14.57).

Females: body length 2.12–2.58. Pedipalps: trochanter 0.27–0.30/0.21 (1.29–1.43), femur 1.61–1.62/0.19–0.20 (8.05–8.53), patella 0.64–0.67/0.23–0.24 (2.67–2.91), chela 2.27–2.29/0.26–0.27 (8.41–8.81), hand 0.78–0.83/0.26– 0.27 (3.00–3.07), movable chelal finger length 1.39–1.43. Chelicera 0.89–0.91/0.36–0.38 (2.39–2.47), movable finger length 0.48–0.49. Carapace 0.74–0.76/0.74–0.76 (0.97–1.03). Leg I: trochanter 0.23–0.24/0.18–0.19 (1.21– 1.33), femur 0.89–0.92/0.09–0.10 (9.20–9.89), patella 0.47/0.09 (5.22), tibia 0.39–0.41/0.07–0.08 (5.13–5.57), tarsus 0.95–0.98/0.07 (13.57–14.00). Leg IV: trochanter 0.35/0.19 (1.84), femoropatella 1.23–1.25/0.27–0.28 (4.39– 4.63), tibia 0.82–0.86/0.12 (6.83–7.17), metatarsus 0.41/0.09 (4.56), tarsus 1.02–1.06/0.07–0.08 (13.25–14.57).

Remarks. Tyrannochthonius gracilis sp. nov. is similar to T. parcidentatus sp. nov. in having intercalary teeth on the fixed chelal finger only and a pointed, triangular epistome, but differs by a smaller body size but longer appendages (body length 1.96–2.06 (♂), 2.12–2.58 (♀) vs. 2.29–2.62 (♂), 2.64–2.66 (♀) mm; chela length 2.08–2.11 (♂), 2.27–2.29 (♀) vs. 1.89–1.93 (♂), 2.02–2.05 (♀) mm) and more fixed chelal finger teeth (42‒45 vs. 30‒31).

Tyrannochthonius gracilis sp. nov. can be distinguished from T. akaelus , T. antridraconis and T. ganshuanensis by the presence of intercalary teeth on the fixed chelal finger only, from T. harveyi by the presence of intercalary teeth on the fixed chelal finger, from T. chixing and T. zhai by the number of setae on tergites I–IV (2 vs. 4) ( Mahnert 2009; Gao et al. 2018, 2020).

Distribution. Known only from the type locality.

Figures

FIGURE 37. Xianren Cave, type locality of Tyrannochthonius gracilis sp. nov., A. Entrance; B. Inside the cave entrance; C. Area where T. gracilis sp. nov. specimens were collected (red arrow); D. Live female of T. gracilis sp. nov. in its natural environment.

FIGURE38.Tyrannochthoniusgracilissp.nov.,A.Holotypemale,habitus(dorsalview);B.Paratypefemale,habitus(dorsalview).

FIGURE 39. Tyrannochthonius gracilis sp. nov., holotype male (A–F), paratype female (G): A. Left chela (lateral view); B. Left chela (dorsal view); C. Carapace (dorsal view); D. Left chelicera (dorsal view); E. Left pedipalp (minus chela, dorsal view); F. Male genital area (ventral view); G. Female genital area (ventral view).

FIGURE 40. Tyrannochthonius gracilis sp. nov., holotype male: A. Carapace (dorsal view); B. Left chelicera (dorsal view), with details of teeth; C. Coxal spines on coxae II (ventral view); D. Left pedipalp (minus chela, dorsal view); E. Rallum. Scale bars: 0.20 mm (A–B, D); 0.10 mm (C, E).

FIGURE 41. Tyrannochthonius gracilis sp. nov., holotype male: A. Left chela (lateral view), with details of teeth and with trichobothrial pattern; B. Left chela (dorsal view); C. Leg I (lateral view); D. Leg IV (lateral view). Scale bars: 0.20 mm.