Tyrannochthonius yanwuensis, Sun & Guo & Zhang, 2025

Sun, Jianzhou, Guo, Xiangbo & Zhang, Feng, 2025, Three new cave-dwelling species of Tyrannochthonius Chamberlin, 1929 (Pseudoscorpiones, Chthoniidae) from Guangxi, China, Subterranean Biology 51, pp. 115-133 : 115-133

Tyrannochthonius yanwuensis sp. nov.

Figs 9 , 10 , 11

Type material.

Holotype • ♂ (Ps. - MHBU -GX 2024042801 ): China, Guangxi, Baise City, Leye County, Yanwu Cave [24.823900 ° N, 106.431500 ° E], 695 m a. s. l., 28 April 2024, Sunbin Huang, Mingzhi Zhao, Yan Li & Rong Chen leg.

Etymology.

Named after the type locality, Yanwu Cave.

Diagnosis.

(♂) Moderately sized troglomorphic species with elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated, epistome distinctly triangular; posterior margin of carapace with two setae; tergites I – IV each with two setae. Pedipalps slender, femur 7.23 times longer than broad (length 0.94); chela 8.73 times longer than broad (length 1.31); both chelal fingers with intercalary teeth, and fixed finger teeth strongly heterodentate, movable finger teeth strongly retrorse; sb midway between st and b.

Description.

Adult male (Figs 9 – 11 ).

Color generally pale yellow, chelicerae, carapace, pedipalps and tergites slightly darker black, soft parts pale.

Cephalothorax (Figs 10 E , 11 D ): carapace nearly subquadrate, 0.96 times as long as broad, weakly constricted basally; posterior region with squamous sculpturing laterally, other area smooth, without furrows; anterior margin slightly serrate; epistome triangular, without eyes or eyespots; with 18 setae arranged s 4 s: 4: 4: 2: 2, most setae acuminate, sturdy, long and gently curved, anterolateral setae much shorter than others; with three pairs of lyrifissures, first and second pair situated middle and flank to the setae of ocular row, third pair situated lateral to the sole pair of setae of posterior row. Manducatory process with two acuminate distal setae, anterior seta more than 1 / 2 length of medial seta; apex of coxa I with a rounded anteromedial process; coxae II with 10–11 terminally indented coxal spines on each side, set as an oblique and arched row, central spines slightly longer than the others (Fig. 11 F ); intercoxal tubercle absent; chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5.

Chelicera (Figs 10 D , 11 C ): almost as long as carapace, 2.32 times as long as broad; five setae and two lyrifissures (exterior condylar lyrifissure and exterior lyrifissure) present on hand, all setae acuminate, ventrobasal setae shorter than others; movable finger with one medial seta. Cheliceral hand with moderate wrinkle on both ventral and dorsal sides. Both fingers well provided with teeth, fixed finger with 18 teeth, distal one largest; movable finger with 12 contiguous small teeth; galea completely vestigial (Fig. 11 C ). Serrula exterior with 23 and serrula interior with 16 blades. Rallum with eight blades, the distal one longest, with fine barbules and slightly set apart from the other blades, latter tightly grouped and with long pinnae, some of which are subdivided (Fig. 11 E ).

Pedipalp (Figs 10 A, B, E , 11 A, B, G ): trochanter 1.86, femur 7.23, patella 3.21, chela 8.73, hand 2.67 times as long as broad; femur 2.09 times as long as patella; movable chelal finger 2.22 times as long as hand and 0.68 times as long as chela. Setae generally long and acuminate. Chelal hand not constricted towards fingers, apodeme complex of movable chelal finger slightly sclerotized. Fixed chelal finger and hand with eight trichobothria, movable chelal finger with four trichobothria, ib and isb situated close together, submedially on dorsum of chelal hand; eb, esb and ist at base of fixed chelal finger; esb slightly distal eb and ist slightly distal to esb; it slightly distal to est, situated subdistally; et slightly near to tip of fixed chelal finger, slightly close to chelal teeth; dx situated distal to et; sb midway between st and b; b and t situated subdistally, t slightly distal to it and distal to b; est situated proximal to b and close to it (Figs 10 A , 11 A ). Microsetae (chemosensory setae) present on dorsum of chelal hand (Figs 10 B , 11 B ). Both chelal fingers with a row of teeth, spaced regularly along the margin, teeth smaller distally and proximally: fixed finger with 45 well-spaced, strongly pointed teeth and six intercalary microdenticles at the terminal; movable finger with 47 well-spaced, pointed retrorse teeth with and seven intercalary microdenticles at the terminal.

Opisthosoma: generally typical, pleural membrane finely granulated. All tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I – XII: 2: 2: 2: 2: 4: 4: 4: 5: 5: 4: T 2 T: 0. Sternal chaetotaxy IV – XII: 10: 8: 8: 7: 7: 8: 7: -: 2. Genital region: sternite II with ten setae scattered on median area, genital opening slit-like, sternite III with a row of 16 setae (Fig. 10 C ).

Legs (Fig. 11 H – I ): Leg I: femur 1.90 times as long as patella; tarsus 2.27 times as long as tibia. Leg IV: femoropatella 3.90 times as long as deep; tibia 6.33 times as long as deep; with basal tactile setae on both tarsal segments: basitarsus 4.17 times as long as deep (TS = 0.28), telotarsus 12.80 times as long as deep and 2.56 times as long as basitarsus (TS = 0.28). Setae of leg I (trochanter to tibia) 3: 13: 7: 9, setae of leg IV (trochanter to basitarsus) 2: 3: 5: 8: 9. Arolium not divided, slightly shorter than the simple claws.

Dimensions (length / breadth or, in the case of the legs, length / depth in mm; ratios in parentheses). Male: body length 1.36. Pedipalps: trochanter 0.26 / 0.14 (1.86), femur 0.94 / 0.13 (7.23), patella 0.45 / 0.14 (3.21), chela 1.31 / 0.15 (8.73), hand 0.40 / 0.15 (2.67), movable chelal finger length 0.89. Chelicera 0.58 / 0.25 (2.32), movable finger length 0.32. Carapace 0.51 / 0.53 (0.96). Leg I: trochanter 0.18 / 0.13 (1.38), femur 0.55 / 0.07 (7.86), patella 0.29 / 0.07 (4.14), tibia 0.26 / 0.05 (5.20), tarsus 0.59 / 0.05 (11.80). Leg IV: trochanter 0.24 / 0.16 (1.50), femoropatella 0.82 / 0.21 (3.90), tibia 0.57 / 0.09 (6.33), basitarsus 0.25 / 0.06 (4.17), telotarsus 0.64 / 0.05 (12.80).

Distribution.

Known only from the type locality (Guangxi Zhuang Autonomous Region, China).

Figures

Figure 9. Tyrannochthonius yanwuensis sp. nov., holotype male (dorsal view). Scale bar: 0.50 mm.

Figure 10. Tyrannochthonius yanwuensis sp. nov., holotype male: A left chela (lateral view) B left chela (dorsal view) C male genital area (ventral view) D left chelicera (dorsal view) E carapace (dorsal view) F left pedipalp (minus chela, dorsal view). Scale bars: 0.20 mm (A, B, F); 0.10 mm (C – E).

Figure 11. Tyrannochthonius yanwuensis sp. nov., male: A left chela (lateral view), with details of teeth and trichobothrial pattern B left chela (dorsal view) C left chelicera (dorsal view), with details of teeth D carapace (dorsal view) E rallum F coxal spines on coxae II (ventral view) G left pedipalp (minus chela, dorsal view) H leg I (lateral view) I leg IV (lateral view). Scale bars: 0.20 mm (A, B, G); 0.10 mm (C – F, H, I).