Lagynochthonius infirmus, Sun, Guo & Zhang, 2024

Lagynochthonius infirmus sp. nov.

Chinese name. 弱Dȗ伪Dz

Figs 27–30 View FIGURE 27 View FIGURE 28 View FIGURE 29 View FIGURE 30

Type material. Holotype ♂ (Ps.- MHBU-SC2020083001 ): China, Sichuan Province, Luzhou City, Gulin County, Guanniu Cave 2 [28.038775°N, 105.812703°E], 890 m a.s.l., 30 August 2020, Zegang Feng, Hongru Xu & Yangmeng Hou leg. GoogleMaps Paratypes: 4 ♀ (Ps.- MHBU-SC2020083002–05 ), all with the same data as the holotype GoogleMaps .

Etymology. The specific name is derived from the Latin word “ infirmus ”, meaning feeble, which refers to the two eyespots.

Diagnosis. (♂ ♀). Moderately sized hypogean species; carapace with two eyespots, anterior margin smooth and epistome small and triangular; tergites Ⅰ–ⅠV each with four setae. Pedipalps slender, chela 8.47 (♂), 7.57–8.05 (♀) times as long as broad; femur 8.69 (♂), 7.75–8.13 (♀) times as long as broad; both chelal fingers without intercalary teeth and a modified accessory tooth (td) on prolateral-retrolateral face; chemosensory setae (sc) present on dorsum of chelal hand.

Description. Adult male (holotype) ( Figs 27A View FIGURE 27 , 28A– D, 28F–H View FIGURE 28 , 29 View FIGURE 29 , 30 View FIGURE 30 ).

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

Cephalothorax ( Figs 27D, F View FIGURE 27 , 28A View FIGURE 28 ): carapace nearly subquadrate, 1.05 times as long as broad, weakly constricted basally; posterior region with squamous sculpturing laterally, other area smooth, without furrows; anterior margin smooth, without serrations; epistome strongly point, with two eyespots; with 18 setae arranged s4s: 4: 4: 2: 2, most setae heavy, 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 less than 1/2 length of medial seta; apex of coxa I with a rounded anteromedial process; coxae II with 8 terminally indented coxal spines on each side, set as an oblique and arc row, central spines slightly longer than the others ( Fig. 29D View FIGURE 29 ); intercoxal tubercle absent; chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5.

Chelicera ( Figs28C View FIGURE 28 , 29B View FIGURE 29 ): almost as long as carapace, 1.84 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 13 teeth, distal one largest; movable finger with 16 retrorse contiguous small teeth; galea completely vestigial ( Fig. 28B View FIGURE 28 ). Serrula exterior with 25–27 and serrula interior with 13 blades. Rallum with eight 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. 29C View FIGURE 29 ).

Pedipalp ( Figs 28A–B, 28G View FIGURE 28 , 29E View FIGURE 29 , 30A–B View FIGURE 30 ): trochanter 1.53, femur 8.69, patella 2.93, chela 8.47, hand 3.32 times as long as broad; femur 2.56 times as long as patella; movable chelal finger 1.56 times as long as hand and 0.61 times as long as chela. Setae generally long and acuminate. Chelal hand gradually constricted towards fingers, apodeme complex of movable chelal finger strongly 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 slightly closer to st than to b; b and t situated subdistally, t situated at the same level as it and distal to b; est situated distal to b and close to it ( Figs. 28A View FIGURE 28 , 30A View FIGURE 30 ). Microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs. 28B View FIGURE 28 , 30B View FIGURE 30 ). Both chelal fingers with a row of teeth, spaced regularly along the margin, teeth smaller distally and proximally: fixed finger with 23 well-spaced, pointed teeth, and a modified accessory tooth on prolateral-retrolateral face (td, slightly distal to dx); movable finger with 13 well-spaced, pointed teeth, plus 10 vestigial, rounded and contiguous basal teeth.

Opisthosoma: generally typical, pleural membrane finely granulated. All tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 4: 4: 4: 4: 4: 4: 4: 4: 5: 4: T2T: 0. Sternal chaetotaxy IV– XII: 8: 9: 8: 9: 9: 14: 9: -: 2. Genital region: sternite II with 6 setae scattered on median area, genital opening slit-like, sternite III with 22 setae ( Fig. 28H View FIGURE 28 ).

Legs ( Fig. 30C–D View FIGURE 30 ): fine granulation present on anterodorsal faces of femur IV and patella IV. Leg Ⅰ: femur 1.88 times as long as patella; tarsus 2.45 times as long as tibia. Leg IV: femoropatella 3.72 times as long as deep; tibia 6.40 times as long as deep; with basal tactile setae on both tarsal segments: basitarsus 4.00 times as long as deep (TS = 0.31), telotarsus 15.80 times as long as deep and 2.47 times as long as basitarsus (TS = 0.23). Setae of leg I (trochanter to tibia) 2: 8: 8: 10, setae of leg IV (trochanter to basitarsus) 2: 3: 4: 10: 9. Arolium not divided, slightly shorter than the simple claws.

Adult females (paratypes) ( Figs 27B View FIGURE 27 , 28I View FIGURE 28 ). Mostly same as male; tergal chaetotaxy Ⅰ–ⅩII: 4: 4: 4: 4: 4: 4: 4: 4–5: 5: 4: T2 T: 0; sternal chaetotaxy IV–ⅩII: 6–8: 8–10: 8–9: 9: 9–11: 9–11: 9–11: -: 2. Genital region : sternite II with 10 setae scattered on median area, sternite III with a row of 6–10 setae.

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Male: body length 1.87. Pedipalps: trochanter 0.23/0.15 (1.53), femur 1.13/0.13 (8.69), patella 0.44/0.15 (2.93), chela 1.61/0.19 (8.47), hand 0.63/0.19 (3.32), movable chelal finger length 0.98. Chelicera 0.57/0.31 (1.84), movable finger length 0.31. Carapace 0.58/0.55 (1.05). Leg I: trochanter 0.18/0.11 (1.64), femur 0.64/0.08 (8.00), patella 0.34/0.07 (4.86), tibia 0.29/0.06 (4.83), tarsus 0.71/0.05 (14.20). Leg IV: trochanter 0.23/0.13 (1.77), femoropatella 0.93/0.25 (3.72), tibia 0.64/0.10 (6.40), basitarsus 0.32/0.08 (4.00), telotarsus 0.79/0.05 (15.80).

Females:body length1.86–2.49.Pedipalps:trochanter 0.33–0.35/0.16–0.17 (2.06), femur 1.22–1.27/0.15–0.16 (7.75–8.13), patella 0.45–0.51/0.18 (2.50–2.83), chela 1.69–1.77/0.22–0.23 (7.57–8.05), hand 0.67–0.70/0.22– 0.23 (3.00–3.18), movable chelal finger length 0.99–1.27. Chelicera 0.63–0.69/0.34–0.38 (1.80–1.82), movable finger length 0.33–0.36. Carapace 0.58–0.63/0.64–0.67 (0.88–0.97). Leg I: trochanter 0.16–0.21/0.11–0.16 (1.30– 1.67), femur 0.66–0.73/0.08–0.10 (6.70–8.25), patella 0.30–0.35/0.07–0.08 (4.13–4.75), tibia 0.31–0.33/0.06 (5.17–5.50), tarsus 0.71–0.78/0.05–0.06 (11.83–14.40). Leg IV: trochanter 0.24–0.30/0.14–0.15 (1.60–2.14), femoropatella 0.95–1.05/0.24–0.26 (3.65–4.20), tibia 0.63–0.69/0.09–0.10 (6.30–7.22), basitarsus 0.29– 0.32/0.08–0.09 (3.56–4.00), telotarsus 0.76–0.84/0.05– 0.06 (12.83–15.20).

Remarks. Lagynochthonius infirmus sp. nov. differs from all other hypogean Lagynochthonius species except L. crassus and L. latipectus by the absence of intercalary teeth on chelal fingers and the presence of two eyespots on the carapace. It differs from L. crassus and L. latipectus by the small and triangular epistome (obtuse, small, round in L. crassus and L. latipectus ) and its longer chela (1.61 mm (♂), 1.69–1.77 mm (♀) compared to 1.54–1.57 mm (♂), 1.55–1.60 mm (♀) in L. crassus and 1.32–1.38 mm (♂), 1.35–1.50 mm (♀) in L. latipectus ) ( Hou et al. 2022b, 2023a).

Distribution. Known only from the type locality, Guanniu Cave 2 ( China, Sichuan Province).