Tyrannochthonius parcidentatus, 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 : 106-108

Tyrannochthonius parcidentatus sp. nov. ‹mffiƟṁae›

Figs 86–90

Type material. Holotype ♂ (Ps.- MHBU-HBUARA#2022-489 - 01 ): China, Guizhou Province, Dafang County, Lvtang Township, Fengchaner Village , Daniu Cave , under the clods and on the cave walls in the deep zone (Temperature: 15°C, Humidity: 85%) [27°3′16.72″N, 105°29′9.31″E], 1574 m a.s.l., 29 July 2022, Yanmeng Hou, Lu Zhang, Jianzhou Sun & Wenlong Fan leg. Paratypes: 1 ♂ (Ps.- MHBU-HBUARA#2022-489 - 02 ), 3 ♀ (Ps.-MSWU-HBUARA#2022-489-03–HBUARA#2022-489-05), all with the same data as the holotype .

Etymology. The specific name is derived from a combination of the Latin word “ parcus ” and “ dentatus ”, meaning few and toothed, respectively, which refers to the low number of intercalary teeth on the fixed chelal finger.

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–III each with 2 setae. Pedipalps slender, femur 9.07–9.13 (♂), 8.41–8.81 (♀) times longer than broad; chela 8.77–9.00 (♂), 7.88–8.42 (♀) times longer than broad; only fixed chelal finger with a few intercalary teeth.

Description. Males (holotype and paratype) ( Figs 87A , 88A–C, E, F, H , 89 , 90 ).

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

Cephalothorax ( Figs 88C , 89A ): carapace 0.98–1.02 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 exterior to the sole pair of setae of posterior row. Chaetotaxy of coxae: P 3, I 3, II 3–4, 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 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. 89C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 88E , 89B ): large, about as long as carapace, 2.34–2.45 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 20–21 teeth, distal one largest; movable finger with 15 retrorse contiguous small teeth; galea completely vestigial ( Fig. 89B ). Serrula exterior with 17–18 and serrula interior with 13–14 blades. Rallum with 7 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. 89E ).

Pedipalp ( Figs 88A, B, H , 89D , 90A, B ): long and slender, trochanter 1.28–1.41, femur 9.07–9.13, patella 2.50, chela 8.77–9.00, hand 3.32–3.38 times longer than broad; femur 2.72–2.74 times longer than patella; movable chelal finger 1.53–1.55 times longer than hand and 0.58 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissure present on patella ( Figs 88H , 89D ). 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 midway between b and st; b and t situated subdistally, t situated distal to b and proximal to est ( Fig. 90A ).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 26–28 macrodenticles, long and pointed, slightly retrorse, plus 3– 4 intercalary microdenticles, 30–31 in total; movable chelal finger with 44–46 macrodenticles (smaller and denser than teeth on fixed chelal finger), slightly retrorse and pointed, without intercalary teeth ( Fig. 90A ). Chelal fingers straight in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs 88B , 90B ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 2: 2: 2: 2–3: 4: 4: 4: 5: 5: 3–4: T2T: 0; tergites VIII and IX each with an unpaired median seta. Sternal chaetotaxy III–XII: 14–16: 12–13: 8: 8: 7–8: 7–8: 7–8: 7: 0: 2. Anterior genital operculum with 11 setae, genital opening slit-like, with 12–15 marginal setae on each side, 36–39 in total ( Fig. 88F ).

Legs ( Fig. 90C, D ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.90–1.93 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.34–2.44 times longer than tibia. Femoropatella of leg IV 4.48–4.63 times longer than deep; tibia 6.64–6.73 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 3.56–3.67 times longer than deep (TS= 0.28–0.30), tarsus 15.50–15.67 times longer than deep and 2.85–2.91 times longer than metatarsus (TS= 0.32–0.33). Arolium slightly shorter than the claws, not divided; claws simple.

Adult females (paratypes) ( Figs 87B , 88D, G ). Mostly same as males, but a little larger; with 17–18 setae of carapace arranged s4s: 4: 4: 2: 2; chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5; tergal chaetotaxy I–XII: 2: 2: 2: 2: 4: 4: 4: 5: 5: 4: T2T: 0; sternal chaetotaxy IV–XII: 12: 8–9: 8: 7: 7: 7: 7: 0: 2; anterior genital operculum with 10–11 setae, posterior margin with 13–14 marginal setae, 23–25 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 3.67–4.00 times longer than deep (TS= 0.27–0.28), tarsus 15.00–16.33 times longer than deep and 2.72–2.73 times longer than metatarsus (TS= 0.31–0.37).

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 2.29–2.62. Pedipalps: trochanter 0.23–0.24/0.17–0.18 (1.28–1.41), femur 1.36–1.37/0.15 (9.07–9.13), patella 0.50/0.20 (2.50), chela 1.89–1.93/0.21–0.22 (8.77–9.00), hand 0.71–0.73/0.21–0.22 (3.32–3.38), movable chelal finger length 1.10–1.12. Chelicera 0.68–0.71/0.29 (2.34–2.45), movable finger length 0.37–0.39. Carapace 0.61–0.62/0.61–0.62 (0.98–1.02). Leg I: trochanter 0.19/0.15–0.17 (1.12–1.27), femur 0.74–0.79/0.09 (8.22–8.78), patella 0.39–0.41/0.08 (4.88–5.13), tibia 0.32–0.35/0.06–0.07 (5.00–5.33), tarsus 0.78–0.82/0.06 (13.00–13.67). Leg IV: trochanter 0.27–0.30/0.15–0.16 (1.69–2.00), femoropatella 1.11–1.12/0.24–0.25 (4.48–4.63), tibia 0.73– 0.74/0.11 (6.64–6.73), metatarsus 0.32–0.33/0.09 (3.56–3.67), tarsus 0.93–0.94/0.06 (15.50–15.67).

Females: body length 2.64–2.66. Pedipalps: trochanter 0.23–0.25/0.20 (1.15–1.25), femur 1.41–1.43/0.16–0.17 (8.41–8.81), patella 0.51–0.52/0.20–0.22 (2.36–2.55), chela 2.02–2.05/0.24–0.26 (7.88–8.42), hand 0.75–0.77/0.24– 0.26 (2.96–3.13), movable chelal finger length 1.19. Chelicera 0.75–0.77/0.30–0.31 (2.48–2.50), movable finger length 0.41–0.42. Carapace 0.63–0.65/0.63–0.64 (0.98–1.03). Leg I: trochanter 0.18–0.21/0.16–0.17 (1.13–1.24), femur 0.78–0.80/0.10 (7.80–8.00), patella 0.42/0.08–0.09 (4.67–5.25), tibia 0.35–0.37/0.06 (5.83–6.17), tarsus 0.79–0.84/0.06 (13.17–14.00). Leg IV: trochanter 0.28–0.31/0.17–0.18 (1.65–1.72), femoropatella 1.08–1.16/0.24– 0.25 (4.50–4.64), tibia 0.72–0.75/0.11 (6.55–6.82), metatarsus 0.33–0.36/0.09 (3.67–4.00), tarsus 0.90–0.98/0.06 (15.00–16.33).

Remarks. Tyrannochthonius parcidentatus sp. nov. is similar to T. gracilis sp. nov. in having intercalary teeth on the fixed chelal finger only and a pointed, triangular epistome, but differs by a larger body size but shorter appendages (body length 2.29–2.62 (♂), 2.64–2.66 (♀) vs. 1.96–2.06 (♂), 2.12–2.58 (♀) mm; chela length 1.89–1.93 (♂), 2.02–2.05 (♀) vs. 2.08–2.11 (♂), 2.27–2.29 (♀) mm; movable chelal finger 1.53–1.55 (♂), 1.55–1.59 (♀) times vs. 1.63–1.76 (♂), 1.67–1.83 (♀) times longer than board), fewer fixed chelal finger teeth (30‒31 vs. 42‒45) and the number of blades of rallum (7 vs. 6).

Tyrannochthonius parcidentatus 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–III (2 vs. 4) ( Mahnert 2009; Gao et al. 2018, 2020).

Distribution. Known only from the type locality.

Figures

FIGURE 86. Daniu Cave, type locality of Tyrannochthonius parcidentatus sp. nov., A. Cave location (red arrow); B. Inside the cave entrance; C. Passage where T. parcidentatus sp. nov. specimens were collected; D–E. Areas where T. parcidentatus sp. nov. specimens were collected.

FIGURE 87. Tyrannochthonius parcidentatus sp. nov., A. Holotype male, habitus (dorsal view); B. Paratype female, habitus (dorsal view).

FIGURE 88. Tyrannochthonius parcidentatus 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. Female carapace (dorsal view), indicate epistome with one seta flanking base; 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 89. Tyrannochthonius parcidentatus 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 90. Tyrannochthonius parcidentatus 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.