Tyrannochthonius breviculus, 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 : 31-37

Tyrannochthonius breviculus sp. nov. ‹ÑṚƟṁae›

Figs 22–26

Type material. Holotype ♂ (Ps.- MHBU-HBUARA#2021-202 - 01 ): China, Guizhou Province, Libo County, Maolan Town, Yaochao Village , Yanjia Cave , under stones in the deep zone (Temperature: 13°C, Humidity: 90%) [25°22′41.97″N, 108°3′40.08″E], 609.5 m a.s.l., 1 August 2021, Zegang Feng, Hongru Xu, Liu Fu & Nana Zhan leg. Paratypes: 2 ♂ (Ps.- MHBU-HBUARA#2021-202 - 02 & HBUARA#2021-202-03), 2 ♀ (Ps.-MSWU-HBUARA#2021-202-04 & HBUARA#2021-202-05), all with the same data as the holotype .

Etymology. The specific name is derived from the Latin word “ breviculus ”, meaning short, which refers to the short pedipalps.

Diagnosis (J ♀). Small-sized troglomorphic species with slightly elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated, epistome small, rounded and obtuse; posterior margin of carapace with 2 setae; tergites I–Ⅴ each with 4 setae (more variation in females). Palpal femur 5.10–5.33 (♂), 5.00–5.30 (♀) times longer than broad; chela 5.69–5.85 (♂), 5.57–5.64 (♀) times longer than broad; both chelal fingers with intercalary teeth; chemosensory setae present on dorsum of chelal hand.

Description. Males (holotype and paratypes) ( Figs 23A , 24A–C, E, F, H ).

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

Cephalothorax ( Figs 24C , 25A ): carapace 0.95–0.98 times longer than broad, gently narrowed posteriorly; surface smooth, without furrows; no traces of eyes; anterior margin slightly serrate; epistome small, rounded and obtuse; 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 setae of ocular row, second pair situated lateral 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 8–9 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. 25C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 24E , 25B ): large, about as long as carapace, 2.05–2.11 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 both dorsal and ventral side. Both fingers well provided with teeth, fixed finger with 10–11 teeth, distal one largest; movable finger with 13–15 retrorse contiguous small teeth; galea completely vestigial ( Fig. 25B ). Serrula exterior with 17–18 and serrula interior with 12–14 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. 25E ).

Pedipalp ( Figs 24A, B, H , 25D , 26A, B ): long and slender, trochanter 1.00–1.18, femur 5.10–5.33, patella 2.00–2.09, chela 5.69–5.85, hand 1.85–1.92 times longer than broad; femur 2.09–2.13 times longer than patella; movable chelal finger 2.12–2.13 times longer than hand and 0.69–0.70 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissure present on patella ( Figs 24H , 25D ). 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 and hand. 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 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 midway between st and b; b and t situated subdistally, t situated distal to b and midway between it and est; est situated distal to b ( Fig. 26A ). 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 29–30 macrodenticles, slightly retrorse and pointed, plus 13– 15 intercalary microdenticles, 42–45 in total; movable chelal finger with 9–10 macrodenticles (slightly smaller than teeth on fixed chelal finger), slightly retrorse and pointed, plus 8 intercalary microdenticles and 14–16 vestigial, rounded and contiguous basal teeth, 32–33 in total ( Fig. 26A ). Chelal fingers slightly curved in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs 24B , 26B ).

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: 5: 5: 4: T2T: 0, tergites VI–IX each with an unpaired median seta. Sternal chaetotaxy III–XII: 13–14: 11–13: 8–9: 9: 9: 8–9: 9: 9–10: 0: 2. Anterior genital operculum with 10–11 setae, genital opening slit-like, with 10–12 marginal setae on each side, 32–33 in total ( Fig. 24F ).

Legs ( Fig. 26C, D ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.87–2.00 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.00–2.27 times longer than tibia. Femoropatella of leg IV 2.67 times longer than deep; tibia 4.00–4.43 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 2.80 times longer than deep (TS= 0.36), tarsus 11.33–11.67 times longer than deep and 2.43–2.50 times longer than metatarsus (TS= 0.24–0.29). Arolium slightly shorter than the claws, not divided; claws simple.

Adult females (paratypes) ( Figs 23B , 24D, G ). Mostly same as males, but a little larger; with same chaetotaxy of coxae; tergal chaetotaxy I–XII: 3–4: 2–4: 4–5: 4–5: 5: 5: 5: 5: 5: 4: T2T: 0; sternal chaetotaxy IV–XII: 12–13: 7–9: 8–9: 9: 9: 10: 9: 0: 2; anterior genital operculum with 10 setae, posterior margin with 14–16 marginal setae, 24–26 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 2.33–2.80 times longer than deep (TS= 0.36–0.43), tarsus 11.00–12.00 times longer than deep and 2.36–2.57 times longer than metatarsus (TS= 0.24–0.25).

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 1.24–1.26. Pedipalps: trochanter 0.11–0.13/0.11 (1.00–1.18), femur 0.48–0.51/0.09–0.10 (5.10–5.33), patella 0.23–0.24/0.11–0.12 (2.00–2.09), chela 0.74–0.76/0.13 (5.69–5.85), hand 0.24–0.25/0.13 (1.85–1.92), movable chelal finger length 0.51–0.53. Chelicera 0.38–0.39/0.18–0.19 (2.05–2.11), movable finger length 0.20. Carapace 0.38–0.40/0.40–0.41 (0.95–0.98). Leg I: trochanter 0.10–0.11/0.09 (1.11–1.22), femur 0.28/0.05–0.06 (4.67–5.60), patella 0.14–0.15/0.05 (2.80–3.00), tibia 0.15–0.16/0.04 (3.75–4.00), tarsus 0.32–0.34/0.03 (10.67–11.33). Leg IV: trochanter 0.13–0.14/0.09–0.10 (1.40–1.44), femoropatella 0.40/0.15 (2.67), tibia 0.28–0.31/0.07 (4.00–4.43), metatarsus 0.14/0.05 (2.80), tarsus 0.34–0.35/0.03 (11.33–11.67).

Females: body length 1.33–1.44. Pedipalps: trochanter 0.12–0.14/0.11–0.12 (1.08–1.09), femur 0.53–0.55/0.10– 0.11 (5.00–5.30), patella 0.25–0.26/0.13 (1.92–2.00), chela 0.78–0.79/0.14 (5.57–5.64), hand 0.26–0.27/0.14 (1.86– 1.93), movable chelal finger length 0.53–0.55. Chelicera 0.42–0.43/0.20–0.21 (2.05–2.10), movable finger length 0.22–0.23. Carapace 0.40–0.42/0.42–0.45 (0.93–0.95). Leg I: trochanter 0.11/0.09–0.10 (1.10–1.22), femur 0.27– 0.30/0.06 (4.50–5.00), patella 0.14–0.16/0.05 (2.80–3.20), tibia 0.17/0.04 (4.25), tarsus 0.33–0.35/0.04 (8.25–8.75). Leg IV: trochanter 0.12–0.14/0.09–0.10 (1.33–1.40), femoropatella 0.42–0.46/0.14–0.15 (2.80–3.29), tibia 0.32– 0.33/0.07 (4.57–4.71), metatarsus 0.14/0.05–0.06 (2.33–2.80), tarsus 0.33–0.36/0.03 (11.00–12.00).

Remarks. Tyrannochthonius breviculus sp. nov. is similar to T. yanshanensis sp. nov. in having intercalary teeth on both chelal fingers and a small, rounded and obtuse epistome, but differs by a shorter palp (chela length 0.78–0.79 (♀) vs. 0.91–0.92 (♀) mm; palpal femur 5.00–5.30 (♀) vs. 4.92–5.08 (♀) times longer than board, length 0.53–0.55 (♀) vs. 0.59–0.61 (♀) mm; movable chelal finger 2.04 (♀) vs. 2.17–2.21 (♀) times longer than hand), the number of setae on the tergites VIII‒IX (5 vs. 6), the relative position of trichobothrium sb (sb midway between st and b vs. nearer st than b) and the number of blades of rallum (8 vs. 7).

Tyrannochthonius breviculus sp. nov. can be distinguished from T. chixing , T. harveyi and T. zhai by the presence of intercalary teeth on both chelal fingers, from T. akaelus , T. antridraconis and T. ganshuanensis by a shorter palp (chela length max. 0.79 vs. min. 1.21 mm; palpal femur length max. 0.55 vs. min. 0.90 mm) ( Mahnert 2009; Gao et al. 2018, 2020).

Distribution. Known only from the type locality.

Figures

FIGURE 22. Yanjia Cave, type locality of Tyrannochthonius breviculus sp. nov., A. Entrance; B. Live male of T. breviculus sp. nov. in its natural environment.

FIGURE 23. Tyrannochthonius breviculus sp. nov., A. Holotype male, habitus (dorsal view); B. Paratype female, habitus (dorsal view).

FIGURE 24. Tyrannochthonius breviculus sp. nov., holotype male (A–C, E–F, H), paratype female (D, G): A. Left chela (lateral view); B. Left chela (dorsal view); C. Carapace (dorsal view); D. Eggs (ventral view); 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 25. Tyrannochthonius breviculus 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: 0.10 mm.

FIGURE 26. Tyrannochthonius breviculus 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: 0.10 mm.