Tyrannochthonius arificus, 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 : 19-25

Tyrannochthonius arificus sp. nov. ‹ȐƮƟṁae›

Figs 12–16

Type material. Holotype ♂ (Ps.- MHBU-HBUARA#2022-506 - 01 ): China, Guizhou Province, Anlong County, Dushan Town, Polao Village , Hei Cave , under stones and clods in the deep zone (Temperature: 16°C, Humidity: 65%) [25°18′46.56″N, 105°36′2.69″E], 1067 m a.s.l., 6 August 2022, Yanmeng Hou, Lu Zhang, Jianzhou Sun & Wenlong Fan leg. Paratypes: 3 ♂ (Ps.- MHBU-HBUARA#2022-506 - 02 –HBUARA#2022-506-04), 3 ♀ (Ps.-MSWU-HBUARA#2022-506-05–HBUARA#2022-506-07), all with the same data as the holotype .

Etymology. The specific name is derived from the Latin word “ arificus ”, meaning arid, which refers to the species that lives in a dry environment.

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. Palpal femur 5.27–5.55 (♂), 5.36–5.50 (♀) times longer than broad; chela 6.29–6.62 (♂), 6.07–6.20 (♀) times longer than broad; both chelal fingers with intercalary teeth.

Description. Males (holotype and paratypes) ( Figs 13A , 14A–F, H , 15 , 16 ).

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

Cephalothorax ( Figs 14C, D , 15A ): carapace 0.93–0.95 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 17–18 setae arranged s3–4s: 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 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 10 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. 15C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 14E , 15B ): large, about as long as carapace, 2.05–2.20 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 dorsal side. Both fingers well provided with teeth, fixed finger with 11–12 teeth, distal one largest; movable finger with 11–13 retrorse contiguous small teeth; galea completely vestigial ( Fig. 15B ). Serrula exterior with 18–20 and serrula interior with 11–13 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. 15E ).

Pedipalp ( Figs 14A, B, H , 16A, B ): long and slender, trochanter 1.15–1.25, femur 5.27–5.55, patella 2.15–2.17, chela 6.29–6.62, hand 2.07–2.15 times longer than broad; femur 2.18–2.23 times longer than patella; movable chelal finger 2.10–2.14 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 14H , 15D ). 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 closer to st than to b; b and t situated subdistally, t situated distal to b and at same level as est ( Fig. 16A ). 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 30–32 macrodenticles, slightly retrorse and pointed, plus 25– 26 intercalary microdenticles, 56–57 in total; movable chelal finger with 12–13 macrodenticles (slightly smaller than teeth on fixed chelal finger), slightly retrorse and pointed, plus 10– 11 intercalary microdenticles and 17–19 vestigial, rounded and contiguous basal teeth, 41 in total ( Fig. 16A ). Chelal fingers slightly curved in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs 14B , 16B ).

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: 3: T2T: 0, tergites VI–IX each with an unpaired median seta. Sternal chaetotaxy III–XII: 13–15: 13–14: 10: 9: 9: 9: 9–10: 9: 0: 2. Anterior genital operculum with 10–11 setae, genital opening slit-like, with 11–14 marginal setae on each side, 35–36 in total ( Fig. 14F ).

Legs ( Fig. 16C, D ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.76–1.89 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.22–2.37 times longer than tibia. Femoropatella of leg IV 2.84–3.06 times longer than deep; tibia 4.78–5.00 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 3.17 times longer than deep (TS= 0.26–0.37), tarsus 11.75–14.67 times longer than deep and 2.32–2.47 times longer than metatarsus (TS= 0.25–0.34). Arolium slightly shorter than the claws, not divided; claws simple.

Adult females (paratypes) ( Figs 13B , 14G ). Mostly same as males, but a little larger; chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5; with same tergal chaetotaxy as males; sternal chaetotaxy IV–XII: 14–15: 10: 9–10: 9: 9–10: 9–11: 8–9: 0: 2; anterior genital operculum with 10–11 setae, posterior margin with 14 marginal setae, 24–25 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 3.00–3.50 times longer than deep (TS= 0.33), tarsus 12.00–14.67 times longer than deep and 2.29–2.44 times longer than metatarsus (TS= 0.27–0.29).

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 1.31–1.40. Pedipalps: trochanter 0.15/0.12–0.13 (1.15–1.25), femur 0.58–0.61/0.11 (5.27–5.55), patella 0.26–0.28/0.12–0.13 (2.15–2.17), chela 0.86–0.88/0.13–0.14 (6.29–6.62), hand 0.28–0.29/0.13–0.14 (2.07–2.15), movable chelal finger length 0.60–0.61. Chelicera 0.41–0.44/0.20 (2.05–2.20), movable finger length 0.23–0.24. Carapace 0.41–0.43/0.43–0.46 (0.93–0.95). Leg I: trochanter 0.12/0.10 (1.20), femur 0.36–0.37/0.06–0.07 (5.14– 6.17), patella 0.19–0.21/0.05 (3.80–4.20), tibia 0.18–0.19/0.04 (4.50–4.75), tarsus 0.40–0.45/0.03–0.04 (11.25– 13.33). Leg IV: trochanter 0.16–0.17/0.11–0.12 (1.33–1.55), femoropatella 0.52–0.54/0.17–0.19 (2.84–3.06), tibia 0.40–0.43/0.08–0.09 (4.78–5.00), metatarsus 0.19/0.06 (3.17), tarsus 0.44–0.47/0.03–0.04 (11.75–14.67).

Females: body length 1.62–1.69. Pedipalps: trochanter 0.16–0.17/0.12–0.14 (1.21–1.33), femur 0.59–0.66/0.11– 0.12 (5.36–5.50), patella 0.30–0.32/0.13–0.15 (2.13–2.31), chela 0.91–0.93/0.15 (6.07–6.20), hand 0.31/0.15 (2.07), movable chelal finger length 0.62–0.63. Chelicera 0.45–0.47/0.21–0.23 (2.04–2.14), movable finger length 0.24–0.25. Carapace 0.45–0.48/0.46–0.49 (0.98). Leg I: trochanter 0.12–0.13/0.10–0.11 (1.18–1.20), femur 0.37– 0.39/0.06–0.07 (5.57–6.17), patella 0.19–0.22/0.06 (3.17–3.67), tibia 0.19–0.20/0.04–0.05 (4.00–4.75), tarsus 0.44– 0.45/0.04 (11.00–11.25). Leg IV: trochanter 0.18/0.11 (1.64), femoropatella 0.50–0.56/0.17–0.19 (2.94–2.95), tibia 0.39–0.45/0.08–0.09 (4.88–5.00), metatarsus 0.18–0.21/0.06 (3.00–3.50), tarsus 0.44–0.48/0.03–0.04 (12.00–14.67).

Remarks. Tyrannochthonius arificus 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 the larger body size (body length 1.62–1.69 (♀) vs. 1.29–1.33 (♀) mm; chela 6.07–6.20 (♀) vs. 5.69–5.75 (♀) times longer than board), the number of setae on tergite Ⅴ (4 vs. 5) and tergite Ⅹ (3 vs. 5), more intercalary teeth on the fixed chelal finger (25–26 vs. 14), the number of blades of coxal spines (10 vs. 7–8) and the number of blades of rallum (8 vs. 7).

Tyrannochthonius arificus sp. nov. can be distinguished from T. akaelus , T. ganshuanensis and T. harveyi by the number of setae on the tergites I–II (4 vs. 2), from

T. chixing and T. zhai by the number of setae at the anterior margin of the carapace (6 vs. 4), a shorter palp (chela length max. 0.93 vs. min. 1.21 mm; palpal femur length max. 0.66 vs. min. 0.84 mm) and the presence of intercalary teeth on both chelal fingers, from T. antridraconis by a smaller size (body length max. 1.40 vs. min. 1.80 mm; chela length max. 0.88 vs. min. 1.70 mm) ( Mahnert 2009; Gao et al. 2018, 2020).

Distribution. Known only from the type locality.

Figures

FIGURE 12. Hei Cave, type locality of Tyrannochthonius arificus sp. nov., A. Cave location (red arrow); B. Entrance; C. Inside the cave entrance; D–E. Some narrow tunnels in the cave; F. Area where T. arificus sp. nov. specimens were collected.

FIGURE13.Tyrannochthoniusarificussp.nov.,A.Holotypemale,habitus(dorsalview);B.Paratypefemale,habitus(dorsalview).

FIGURE 14. Tyrannochthonius arificus sp. nov., holotype male (A–C, E–F, H), paratype male (D), paratype female (G): A. Left chela (lateral view); B. Left chela (dorsal view); C. Carapace (dorsal view); D. 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 15. Tyrannochthonius arificus 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 16. Tyrannochthonius arificus 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.