Tyrannochthonius brevispinus, 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 : 37-39

Tyrannochthonius brevispinus sp. nov. ‹ÑḦƟṁae›

Figs 27–31

Type material. Holotype ♂ (Ps.- MHBU-HBUARA#2022-518-01 ): China, Guizhou Province, Danzhai County, Longquan Town, Jinguadong Village , Jingua Cave , under stones about 20 m from the cave entrance (Temperature: 12°C, Humidity: 90%) [26°8′15.94″N, 107°48′25.09″E], 749 m a.s.l., 12 August 2022, Yanmeng Hou, Lu Zhang, Jianzhou Sun & Wenlong Fan leg. Paratype: 1 ♀ (Ps.- MSWU-HBUARA#2022-518-02 ), with the same data as the holotype .

Etymology. The specific name is derived from a combination of the Latin word “ brevis ” and “ spineus ”, meaning short and spined, respectively, which refers to the short coxal spines.

Diagnosis (J ♀). Moderately sized troglomorphic species with elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin and finely denticulated, epistome small and represented by a slight bump; posterior margin of the carapace with 2 setae; tergites I–II each with 2 setae. Pedipalps slender, femur 6.64 (♂), 6.67 (♀) times longer than broad; chela 7.39 (♂), 7.53 (♀) times longer than broad; both chelal fingers without intercalary teeth, movable chelal finger teeth distinctly smaller and denser than fixed chelal finger teeth; chemosensory setae present on dorsum of chelal hand; coxal spines short.

Description. Male (holotype) ( Figs 28A , 29A–F , 30 , 31 ).

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

Cephalothorax ( Figs 29C , 30A ): carapace 1.02 times longer than broad, slightly narrowed posteriorly; surface smooth, without furrows; no traces of eyes; anterior margin slightly serrate; epistome small and represented by a slight 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 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. 30C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 29D , 30B ): large, about as long as carapace, 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 12 teeth, distal one largest; movable finger with 16 retrorse contiguous small teeth; galea represented by a very slight bump on movable finger ( Fig. 30B ). Serrula exterior with 17 and serrula interior with 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. 30E ).

Pedipalp ( Figs 29A, B, E , 31A, B ): long and slender, trochanter 1.33, femur 6.64, patella 2.13, chela 7.39, hand 2.39 times longer than broad; femur 2.74 times longer than patella; movable chelal finger 2.05 times longer than hand and 0.66 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissure present on patella ( Figs 29E , 30D ). 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 proximal to est ( Fig. 31A ). 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 26 macrodenticles, slightly retrorse and pointed; movable chelal finger with 18 macrodenticles (markedly smaller than teeth on fixed chelal finger), continuous, retrorse and pointed, plus 18 small, rounded and contiguous basal teeth, 36 in total ( Fig. 31A ). Chelal fingers slightly curved in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs 29B , 31B ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 2: 2: 4: 4: 4: 4: 4: 5: 5: 4: T2T: 0. Sternal chaetotaxy III–XII: 12: 12: 7: 8: 9: 9: 9: 9: 0: 2. Anterior genital operculum with 10 setae, genital opening slit-like, with 12–14 marginal setae on each side, 36 in total ( Fig. 29F ).

Legs ( Fig. 31C, D ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.76 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.32 times longer than tibia. Femoropatella of leg IV 3.43 times longer than deep; tibia 5.67 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 3.29 times longer than deep (TS= 0.26), tarsus 12.80 times longer than deep and 2.78 times longer than metatarsus (TS= 0.33). Arolium slightly shorter than the claws, not divided; claws simple.

Adult female (paratype) ( Figs 28B , 29G ). Mostly same as male, but a little larger; chaetotaxy of coxae: P 3, I 3, II 3–4, III 5, IV 5; with same tergal chaetotaxy as male; sternal chaetotaxy IV–XII: 12: 8: 9: 9: 9: 9: 9: 0: 2; anterior genital operculum with 10 setae, posterior margin with 12 marginal setae, 22 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 4.00 times longer than deep (TS= 0.25), tarsus 12.40 times longer than deep and 2.58 times longer than metatarsus (TS= 0.31).

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Male: body length 1.73. Pedipalps: trochanter 0.20/0.15 (1.33), femur 0.93/0.14 (6.64), patella 0.34/0.16 (2.13), chela 1.33/0.18 (7.39), hand 0.43/0.18 (2.39), movable chelal finger length 0.88. Chelicera 0.52/0.22 (2.36), movable finger length 0.28. Carapace 0.49/0.48 (1.02). Leg I: trochanter 0.14/0.13 (1.08), femur 0.51/0.07 (7.29), patella 0.29/0.07 (4.14), tibia 0.25/0.05 (5.00), tarsus 0.58/0.05 (11.60). Leg IV: trochanter 0.22/0.14 (1.57), femoropatella 0.72/0.21 (3.43), tibia 0.51/0.09 (5.67), metatarsus 0.23/0.07 (3.29), tarsus 0.64/0.05 (12.80).

Female: body length 2.12. Pedipalps: trochanter 0.21/0.16 (1.31), femur 1.00/0.15 (6.67), patella 0.36/0.17 (2.12), chela 1.43/0.19 (7.53), hand 0.47/0.19 (2.47), movable chelal finger length 0.94. Chelicera 0.58/0.24 (2.42), movable finger length 0.30. Carapace 0.55/0.54 (1.02). Leg I: trochanter 0.14/0.14 (1.00), femur 0.56/0.08 (7.00), patella 0.28/0.07 (4.00), tibia 0.26/0.05 (5.20), tarsus 0.62/0.05 (12.40). Leg IV: trochanter 0.23/0.13 (1.77), femoropatella 0.73/0.21 (3.48), tibia 0.51/0.09 (5.67), metatarsus 0.24/0.06 (4.00), tarsus 0.62/0.05 (12.40).

Remarks. Tyrannochthonius brevispinus sp. nov. is similar to T. oblongus sp. nov. in having a small and slight bump epistome and the same number of setae on tergites I–II (2), but differs by a smaller size (body length 1.73 (♂) vs. 2.18–2.26 (♂) mm; chela 7.39 (♂), 7.53 (♀) vs. 7.27 (♂), 6.78–7.09 (♀) times longer than board, length 1.33 (♂), 1.43 (♀) vs. 1.60 (♂) mm, 1.56 (♀) mm; palpal femur length 0.93 (♂), 1.00 (♀) vs. 1.11–1.17 (♂), 1.09–1.17 (♀) mm), the proportion of movable chelal finger and chelal hand (movable chelal finger 2.05 (♂), 2.00 (♀) vs. 1.74–1.79 (♂), 1.74–1.75 (♀) times longer than hand), the relative position of trichobothrium sb (sb midway between b and st vs. nearer b than st) and the number of blades of rallum (8 vs. 7).

Tyrannochthonius brevispinus sp. nov. can be distinguished from T. akaelus , T. antridraconis , T. chixing , T. ganshuanensis and T. zhai by lacking intercalary teeth on both chelal fingers, from T. harveyi by the number of setae at the anterior margin of the carapace (6 vs. 4), a larger body size (body length min. 1.73 mm vs. max. 1.56 mm; chela length min. 1.33 mm vs. max. 1.30 mm; palpal femur length min. 0.93 mm vs. max. 0.88 mm), the number of setae on tergite III (4 vs. 2) and the number of blades of rallum (8 vs. 6) ( Mahnert 2009; Gao et al. 2018, 2020).

Distribution. Known only from the type locality.

Figures

FIGURE 27. Jingua Cave, type locality of Tyrannochthonius brevispinus sp. nov., A. Entrance; B–C.Area where T. brevispinus sp. nov. specimens were collected; D. Stalactites in the cave.

FIGURE 28. Tyrannochthonius brevispinus sp. nov., A. Holotype male, habitus (dorsal view); B. Paratype female, habitus (dorsal view).

FIGURE 29. Tyrannochthonius brevispinus 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 30. Tyrannochthonius brevispinus 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 31. Tyrannochthonius brevispinus 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.