Tyrannochthonius oblongus, 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 : 99-102

Tyrannochthonius oblongus sp. nov. ‹ḢŔƟṁae›

Figs 81–85

Type material. Holotype ♂ (Ps.-MHBU-GZGY-20-04-01): China, Guizhou Province, Huaxi District, Gaopo Township, Houzi Cave , under stones in the deep zone (Temperature: 16°C, Humidity: 75%) [26°16′50.73″N, 106°49′10.46″E], 1485 m a.s.l., 16 August 2020, Zegang Feng, Hongru Xu & Yanmeng Hou leg. Paratypes: 1 ♂ (Ps.-MHBU-GZGY-20-04-02), with the same data as the holotype; 8 ♂ (Ps.- MHBU-HBUARA#2022-481 - 01 – HBUARA#2022-481-08), 2 ♀ (Ps.- MSWU-HBUARA#2022-481 - 09 & HBUARA#2022-481-10), with the same location as the holotype, 26 July 2022, Yanmeng Hou, Lu Zhang & Jianzhou Sun leg.

Etymology. The specific name is derived from the Latin word “ oblongus ” (= rectangular), which refers to the presence of a nearly rectangular carapace.

Diagnosis (J ♀). Moderately sized troglomorphic species with elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated, epistome small and obtuse, represented by a bump; posterior margin of carapace with 2 setae; tergites I–II each with 2 setae. Pedipalps slender, femur 7.80–7.93 (♂), 7.27–7.80 (♀) times longer than broad; chela 7.27 (♂), 6.78–7.09 (♀) times longer than broad; both chelal fingers without intercalary teeth.

Description. Males (holotype and paratypes) ( Figs 81F , 82A , 83A–F , 84 , 85 ).

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

Cephalothorax ( Figs 83C , 84A ): carapace 1.05–1.09 times longer than broad, only slightly narrowed posteriorly resulting in rectangular appearance; surface smooth, without furrows; no traces of eyes; anterior margin slightly serrate; epistome small and obtuse, represented by a bump, 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 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. 84C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 83D , 84B ): large, about as long as carapace, 2.32–2.36 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 15–17 teeth, distal one largest; movable finger with 17–18 retrorse contiguous small teeth; galea completely vestigial ( Fig. 84B ). Serrula exterior with 17–19 and serrula interior with 13–15 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. 84E ).

Pedipalp ( Figs 83A, B, E , 84D , 85A, B ): long and slender, trochanter 1.28–1.33, femur 7.80–7.93, patella 2.41–2.67, chela 7.27, hand 2.59–2.64 times longer than broad; femur 2.78–2.85 times longer than patella; movable chelal finger 1.74–1.79 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 83E , 84D ). 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 at same level as est and distal to b ( Fig. 85A ). A tiny antiaxial lyrifissure present at base of fixed chelal finger (situated distal to ist). Both chelal fingers with a row of teeth, homodentate, 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 23–25 macrodenticles, slightly retrorse, long and pointed; movable chelal finger with 22–23 macrodenticles (markedly smaller than teeth on fixed chelal finger), continuous and retrorse, almost prostrate, plus 8–10 vestigial, rounded and contiguous basal teeth, 30–33 in total ( Fig. 85A ). Chelal fingers slightly curved in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs 83B , 85B ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 2: 2: 3–4: 4: 4: 4: 4: 4: 4–6: 4: T2T: 0. Sternal chaetotaxy III–XII: 14–15: 10–13: 8–9: 8–9: 8–9: 9–10: 10: 7–8: 0: 2. Anterior genital operculum with 10–11 setae, genital opening slit-like, with 12–14 marginal setae on each side, 35–37 in total ( Fig. 83F ).

Legs ( Fig. 85C, D ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.85–1.97 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.63–2.66 times longer than tibia. Femoropatella of leg IV 4.90–4.95 times longer than deep; tibia 7.20–8.00 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 4.57–5.14 times longer than deep (TS= 0.28), tarsus 14.83–15.00 times longer than deep and 2.47–2.81 times longer than metatarsus (TS= 0.31–0.32). Arolium slightly shorter than the claws, not divided; claws simple.

Adult females (paratypes) ( Figs 82B , 83G ). Mostly same as males, but a little larger; with same chaetotaxy of coxae as males; tergal chaetotaxy I–XII: 2: 2: 4: 4: 4: 4: 4: 4: 4: 4: T2T: 0; sternal chaetotaxy IV–XII: 10–11: 8–9: 7–8: 7–9: 8–9: 9: 7: 0: 2; anterior genital operculum with 10–12 setae, posterior margin with 14–15 marginal setae, 24–27 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 3.88–4.57 times longer than deep (TS= 0.28–0.29), tarsus 13.83–17.00 times longer than deep and 2.66–2.68 times longer than metatarsus (TS= 0.29–0.30).

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 2.18–2.26. Pedipalps: trochanter 0.20–0.23/0.15–0.18 (1.28–1.33), femur 1.11–1.17/0.14–0.15 (7.80–7.93), patella 0.40–0.41/0.15–0.17 (2.41–2.67), chela 1.60/0.22 (7.27), hand 0.57–0.58/0.22 (2.59–2.64), movable chelal finger length 1.01–1.02. Chelicera 0.58–0.59/0.25 (2.32–2.36), movable finger length 0.32. Carapace 0.59– 0.62/0.56–0.57 (1.05–1.09). Leg I: trochanter 0.17/0.15–0.16 (1.06–1.13), femur 0.67–0.72/0.08–0.09 (8.00–8.38), patella 0.34–0.39/0.08 (4.25–4.88), tibia 0.29–0.30/0.06 (4.83–5.00), tarsus 0.77–0.79/0.06 (12.83–13.17). Leg IV: trochanter 0.25–0.30/0.15–0.17 (1.67–1.76), femoropatella 0.99–1.03/0.20–0.21 (4.90–4.95), tibia 0.72/0.09–0.10 (7.20–8.00), metatarsus 0.32–0.36/0.07 (4.57–5.14), tarsus 0.89–0.90/0.06 (14.83–15.00).

Females: body length 2.33–2.53. Pedipalps: trochanter 0.21–0.23/0.16–0.17 (1.24–1.44), femur 1.09–1.17/0.15 (7.27–7.80), patella 0.36–0.42/0.17–0.18 (2.12–2.33), chela 1.56/0.22–0.23 (6.78–7.09), hand 0.56–0.57/0.22–0.23 (2.48–2.55), movable chelal finger length 0.98–0.99. Chelicera 0.59/0.25–0.26 (2.27–2.36), movable finger length 0.31. Carapace 0.57–0.59/0.56 (1.02–1.05). Leg I: trochanter 0.17/0.14–0.15 (1.13–1.21), femur 0.67/0.08 (8.38), patella 0.37/0.07 (5.29), tibia 0.28/0.05–0.07 (4.00–5.60), tarsus 0.70–0.72/0.05–0.06 (12.00–14.00). Leg IV: trochanter 0.27–0.28/0.15–0.16 (1.75–1.80), femoropatella 0.96–0.97/0.20 (4.80–4.85), tibia 0.65–0.68/0.09 (7.22– 7.56), metatarsus 0.31–0.32/0.07–0.08 (3.88–4.57), tarsus 0.83–0.85/0.05–0.06 (13.83–17.00).

Remarks. Tyrannochthonius oblongus sp. nov. is similar to T. brevispinus sp. nov. in having the same number of setae on tergites I–II (2) and lacking intercalary teeth on both chelal fingers, but differs by a larger body size (body length min. 2.18 mm vs. max. 2.12 mm; chela min. 1.56 mm vs. max. 1.43 mm; palpal femur length min. 1.09 mm vs. max. 1.00 mm; movable chelal finger 1.74–1.79 (♂), 1.74–1.75 (♀) vs. 2.05 (♂), 2.00 (♀) times longer than hand), the relative position of trichobothrium sb (sb nearer b than st vs. midway between b and st) and the number of blades of rallum (7 vs. 8).

Tyrannochthonius oblongus sp. nov. can be distinguished from T. akaelus , T. antridraconis , T. chixing , T. ganshuanensis and T. zhai by lacking intercalary teeth on the fixed chelal finger, from T. harveyi by the number of setae at the anterior margin of the carapace (6 vs. 4) and a slender palp (chela 7.27 (♂), 6.78–7.09 (♀) vs. 7.50 (♂), 7.22 (♀) times longer than board, length min. 1.56 mm vs. max. 1.30 mm; palpal femur 7.80–7.93 (♂), 7.27–7.80 (♀) vs. 6.29 (♂), 5.80 (♀) times longer than board, length min. 1.09 mm vs. max. 0.88 mm) ( Mahnert 2009; Gao et al. 2018, 2020).

Distribution. Known only from the type locality.

Figures

FIGURE 81. Houzi Cave, type locality of Tyrannochthonius oblongus sp. nov., A. Cave location (red arrow); B. Entrance; C. Inside the cave entrance; D–E. Area where T. oblongus sp. nov. specimens were collected (white arrow); F. Live male of T. oblongus sp. nov. in its natural environment.

FIGURE82.Tyrannochthoniusoblongussp.nov.,A.Holotypemale,habitus(dorsalview);B.Paratypefemale,habitus(dorsalview).

FIGURE 83. Tyrannochthonius oblongus 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 84. Tyrannochthonius oblongus 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 85. Tyrannochthonius oblongus 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.