Tyrannochthonius infirmus, 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 : 61-67

Tyrannochthonius infirmus sp. nov. ‹NjṄƟṁae›

Figs 47–51

Type material. Holotype ♂ (Ps.- MHBU-GZC190804-01 ): China, Guizhou Province, Pu’an County, Qingshan Town, Xiajiehe Village , Liujiadadong Cave , under stones and clods in the deep zone (Temperature: 13°C, Humidity: 90%) [25°28′6.88″N, 105°0′19.57″E], 1559 m a.s.l., 4 August 2019, Zegang Feng, Zhaoyi Li & Chen Zhang leg. Paratypes: 3 ♂ (Ps.- MHBU-GZC190804-02 – GZC190804-04 ) , 5 ♀ (Ps.- MSWU-GZC190804-05 – GZC190804-09 ), all with the same data as the holotype .

Etymology. The specific name is derived from the Latin word “ infirmus ”, meaning weak, which refers to the presence of a pair of weak eyespots.

Diagnosis (J ♀). Moderately sized troglomorphic species with elongated appendages; carapace with a pair of anterior eyespots only; anterior margin of carapace thin, finely denticulated, epistome small and pointed, triangular; posterior margin of carapace with 2 setae; tergites I–Ⅴ each with 4 setae. Pedipalps slender, femur 6.72–6.88 (♂), 6.47–6.94 (♀) times longer than broad; chela 7.27–7.42 (♂), 6.28–6.83 (♀) times longer than broad; both chelal fingers with intercalary teeth.

Description. Males (holotype and paratypes) ( Figs 48A , 49A–F, H , 50 , 51 ).

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

Cephalothorax ( Figs 49C, D , 50A ): carapace 0.97–0.99 times longer than broad, gently narrowed posteriorly; surface smooth, without furrows; anterior eyes reduced into eyespots, posterior eyes reduced completely; 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 exterior 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 11–13 terminally indented coxal spines on each side, set as an oblique row, longer spines present in the middle of the row, becoming shorter distally and proximally and incised for about half their length ( Fig. 50C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 49E , 50B ): large, about as long as carapace, 2.29–2.30 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 12–14 teeth, distal one largest; movable finger with 12–13 retrorse contiguous small teeth; galea completely vestigial ( Fig. 50B ). Serrula exterior with 18–21 and serrula interior with 13–15 blades. Rallum with 8 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. 50E ).

Pedipalp ( Figs 49A, B, H , 50D , 51A, B ): long and slender, trochanter 1.42–1751, femur 6.72–6.88, patella 2.09–2.32, chela 7.27–7.42, hand 2.64–2.67 times longer than broad; femur 2.50–2.63 times longer than patella; movable chelal finger 1.74–1.78 times longer than hand and 0.63–0.64 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissure present on patella ( Figs 49H , 50D ). 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 midway between it and est; est situated distal to b ( Fig. 51A ). 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 28–31 macrodenticles, slightly retrorse and pointed, plus 20– 21 intercalary microdenticles, 48–52 in total; movable chelal finger with 25–26 macrodenticles (slightly smaller than teeth on fixed chelal finger), slightly retrorse and pointed, plus 18– 19 intercalary microdenticles and 8–10 vestigial, rounded and contiguous basal teeth, 52–54 in total ( Fig. 51A ). Chelal fingers straight in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs 49B , 51B ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 4: 4: 4: 4: 4: 5: 5–6: 5: 5: 4: T2T: 0; tergites VII–IX each with an unpaired median seta. Sternal chaetotaxy III–XII: 12–13: 12–13: 8–9: 10: 9–10: 8–10: 9–10: 9–10: 0: 2. Anterior genital operculum with 10–11 setae, genital opening slit-like, with 20–23 marginal setae on each side, 53 in total ( Fig. 49F ).

Legs ( Fig. 51C, D ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.92–2.09 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.44–2.59 times longer than tibia. Femoropatella of leg IV 3.59–3.85 times longer than deep; tibia 6.25–6.58 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 3.56–3.60 times longer than deep (TS= 0.28), tarsus 12.43–13.83 times longer than deep and 2.42–2.59 times longer than metatarsus (TS= 0.36–0.37). Arolium slightly shorter than the claws, not divided; claws simple.

Adult females (paratypes) ( Figs 48B , 49G ). Mostly same as males, but a little larger; with same chaetotaxy of coxae as males; tergal chaetotaxy I–XII: 4: 4: 4: 4: 4: 4–5: 5–6: 5–7: 6: 4: T2T: 0; sternal chaetotaxy IV–XII: 11–13: 9: 10: 9–10: 9–10: 10–11: 10: 0: 2; anterior genital operculum with 10 setae, posterior margin with 11–13 marginal setae, 21–23 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 3.44–3.56 times longer than deep (TS= 0.28–0.29), tarsus 12.29–13.50 times longer than deep and 2.53–2.77 times longer than metatarsus (TS= 0.35–0.38).

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 2.41–2.54. Pedipalps: trochanter 0.27–0.35/0.19–0.20 (1.42–1.75), femur 1.10–1.21/0.16–0.18 (6.72–6.88), patella 0.44–0.46/0.19–0.22 (2.09–2.32), chela 1.60–1.78/0.22–0.24 (7.27–7.42), hand 0.58–0.64/0.22–0.24 (2.64– 2.67), movable chelal finger length 1.01–1.14. Chelicera 0.69–0.71/0.30–0.31 (2.29–2.30), movable finger length 0.37–0.40. Carapace 0.62–0.68/0.64–0.69 (0.97–0.99). Leg I: trochanter 0.19–0.21/0.15–0.17 (1.24–1.27), femur 0.67–0.75/0.09–0.11 (6.82–7.44), patella 0.32–0.39/0.09 (3.56–4.33), tibia 0.29–0.34/0.06–0.08 (4.25–4.83), tarsus 0.75–0.83/0.06–0.07 (11.86–12.50). Leg IV: trochanter 0.31–0.33/0.17–0.19 (1.74–1.82), femoropatella 0.97– 1.04/0.27 (3.59–3.85), tibia 0.75–0.79/0.12 (6.25–6.58), metatarsus 0.32–0.36/0.09–0.10 (3.56–3.60), tarsus 0.83– 0.87/0.06–0.07 (12.43–13.83).

Females: body length 2.50–2.67. Pedipalps: trochanter 0.21–0.24/0.18 (1.17–1.33), femur 1.10–1.18/0.17 (6.47–6.94), patella 0.45/0.20 (2.25), chela 1.57–1.64/0.24–0.25 (6.28–6.83), hand 0.59–0.61/0.24–0.25 (2.36–2.54), movable chelal finger length 1.00–1.04. Chelicera 0.69–0.71/0.32–0.33 (2.15–2.16), movable finger length 0.37– 0.39. Carapace 0.66–0.67/0.69–0.70 (0.94–0.97). Leg I: trochanter 0.17–0.19/0.15–0.16 (1.06–1.27), femur 0.64– 0.68/0.10 (6.40–6.80), patella 0.35/0.08–0.09 (3.89–4.38), tibia 0.28–0.32/0.07–0.08 (4.00), tarsus 0.70–0.77/0.07 (10.00–11.00). Leg IV: trochanter 0.29/0.17 (1.71), femoropatella 0.95–0.97/0.25–0.26 (3.73–3.80), tibia 0.69– 0.72/0.11–0.12 (6.00–6.27), metatarsus 0.31–0.32/0.09 (3.44–3.56), tarsus 0.81–0.86/0.06–0.07 (12.29–13.50).

Remarks. Tyrannochthonius infirmus sp. nov. can be distinguished from other described Chinese troglomorphic Tyrannochthonius species by the presence of a pair of anterior eyespots.

Distribution. Known only from the type locality.

Figures

FIGURE 47. Liujiadadong Cave, type locality of Tyrannochthonius infirmus sp. nov., A. Entrance; B. Inside the cave entrance; C. Area where T. infirmus sp. nov. specimens were collected; D. Live male of T. infirmus sp. nov. in its natural environment; E. Live female of T. infirmus sp. nov. in its natural environment.

FIGURE48.Tyrannochthoniusinfirmussp.nov.,A.Holotypemale,habitus(dorsalview);B.Paratypefemale,habitus(dorsalview).

FIGURE 49. Tyrannochthonius infirmus sp. nov., holotype male (A–F, H), paratype female (G): A. Left chela (lateral view); B. Left chela (dorsal view); C. Carapace (dorsal view); D. Carapace (lateral view), indicate eyespot; E. Left chelicera (dorsal view); F. Male genital area (ventral view); G. Female genital area (ventral view); H. Left pedipalp (minus chela, dorsal view).

FIGURE 50. Tyrannochthonius infirmus 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 51. Tyrannochthonius infirmus 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.