Lagynochthonius apexus, Edward & Harvey, 2008

SUN, JIANZHOU, GUO, XIANGBO & ZHANG, FENG, 2024, A review of the genus Lagynochthonius Beier, 1951 (Pseudoscorpiones, Chthoniidae) from China, Megataxa 12 (2), pp. 177-250 : 183-188

Lagynochthonius apexus sp. nov.

Chinese name. IJẋȗ伪Dz

Figs 3–6

Type material. Holotype ♂ (Ps.- MHBU-SC2022073101 ): China, Sichuan Province, Luzhou City, Gulin County, Shiping Town, Xiangding Village, Huaer Cave [28.02556943°N, 106.01076007°E], 618 m a.s.l., 31 July 2022, Zegang Feng, Liu Fu, Long Hao & Jiaqi Zhao leg. Paratypes: 1 ♂ (Ps.- MHBU-SC2022073102 ) and 5 ♀ (Ps.- MHBU-SC2022073103–07 ), all with the same data as the holotype .

Etymology. The specific name is derived from the Latin word “ apex ”, meaning peak, which refers to the shape of the epistome.

Diagnosis. (♂ ♀). Moderately sized hypogean species; carapace without eyes or eyespots, anterior margin smooth and epistome peak- shaped; tergites Ⅰ–IV each with four setae. Rallum with eight blades. Pedipalps slender, chela 8.44–8.88 (♂), 7.48–8.10 (♀) times as long as broad; femur 9.08 (♂), 8.07–10.08 (♀) 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 males (holotype and paratype) ( Figs 3A , 4A–F , 5 , 6 ).

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

Cephalothorax ( Figs 4D , 5A ): carapace nearly subquadrate, 1.02–1.06 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 peak-shaped, without eyes or 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, anterior two pairs situated middle and flank to the setae of ocular row, the 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 8–11 terminally indented coxal spines on each side, set as an oblique and arc row, central spines slightly longer than the others ( Fig. 5D ); intercoxal tubercle absent; chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5.

Chelicera ( Figs 4C , 5B ): almost as long as carapace, 1.80–1.83 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 16–18 teeth, distal one largest; movable finger with 12–13 retrorse contiguous small teeth; galea completely vestigial ( Fig. 5B ). Serrula exterior with 22 and serrula interior with 13 blades. Rallum with 7–8 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. 5C ).

Pedipalp ( Figs 4A–B, 4E , 5E , 6A–B ): trochanter 1.75–2.00, femur 9.08, patella 2.80–3.00, chela 8.44– 8.88, hand 3.39–3.52 times as long as broad; femur 2.59 times as long as patella; movable chelal finger 0.90–0.91 times as long as hand and 1.49–1.50 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, 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. 4A , 6A ). Microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs. 4B , 6B ). Both chelal fingers with a row of teeth, spaced regularly along the margin, teeth smaller distally and proximally: fixed finger with 22–24 well-spaced, pointed teeth, and a modified accessory tooth on prolateral-retrolateral face (td, slightly distal to dx); movable finger with 13–15 well-spaced, pointed teeth, plus 8–12 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: 8–9: 8–10: 8–9: 9: 8–10: 8–11: -: 2. Genital region: sternite II with 6 setae scattered on median area, genital opening slit-like, sternite III with 24–28 setae ( Fig. 4F ).

Legs ( Fig. 6C–D ): fine granulation present on anterodorsal faces of femur IV and patella IV. Leg Ⅰ: femur 1.82–1.84 times as long as patella; tarsus 2.23–2.39 times as long as tibia. Leg IV: femoropatella 3.71–3.88 times as long as deep; tibia 6.00–6.89 times as long as deep; with basal tactile setae on both tarsal segments: basitarsus 3.63–3.86 times as long as deep (TS = 0.35– 0.37), telotarsus 11.83–14.60 times as long as deep and 2.45–2.70 times as long as basitarsus (TS = 0.27–0.28). Setae of leg I (trochanter to tibia) 2–4: 10–11: 5–8: 8– 13, setae of leg IV (trochanter to basitarsus) 2–3: 3: 4–5: 8–10: 6–7. Arolium not divided, slightly shorter than the simple claws.

Adult female (paratypes) ( Figs 3B , 4G ). Mostly same as male; tergal chaetotaxy Ⅰ–ⅩII: 4: 4: 4: 4: 4: 4: 4: 4–5: 5–6: 3–4: T2 T: 0; sternal chaetotaxy IV–ⅩII: 8: 8–12: 8: 9: 10: 9–11: 7–13: -: 2. Genital region : sternite II with 8–10 setae scattered on median area, sternite III with a row of 12 setae.

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 1.54–1.94. Pedipalps: trochanter 0.28/0.14– 0.16 (1.75–2.00), femur 1.09/0.12 (9.08), patella 0.42/0.14–0.15 (2.80–3.00), chela 1.51–1.52/0.17–0.18 (8.44–8.88), hand 0.60–0.61/0.17–0.18 (3.39–3.52), movable chelal finger length 0.90–0.91. Chelicera 0.54–0.55/0.30 (1.76–1.94), movable finger length 0.30. Carapace 0.54–0.56/0.53 (1.02–1.06). Leg I: trochanter 0.19/0.11–0.13 (1.46–1.73), femur 0.59–0.60/0.09 (6.56–6.67), patella 0.32–0.33/0.07 (4.57–4.71), tibia 0.28–0.30/0.06 (4.67–5.00), tarsus 0.67/0.05 (13.4). Leg IV: trochanter 0.25/0.14–0.16 (1.56–1.79), femoropatella 0.89–0.93/0.24 (3.71–3.88), tibia 0.60–0.62/0.09–0.10 (6.00–6.89), basitarsus 0.27–0.29/0.07–0.08 (3.63–3.86), telotarsus 0.71–0.73/0.05–0.06 (11.83–14.60).

Females: body length 1.49–1.95. Pedipalps: trochanter 0.27–0.34/0.14–0.16 (1.93–2.13), femur 1.00– 1.21/0.12–0.14 (8.07–10.08), patella 0.36–0.48/0.14– 0.17 (2.57–2.88), chela 1.39–1.62/0.18–0.21 (7.48–8.10), hand 0.55–0.66/0.18–0.21 (3.00–3.30), movable chelal finger length 0.83–0.98. Chelicera 0.53–0.59/0.28–0.33 (1.77–1.89), movable finger length 0.30–0.34. Carapace 0.48–0.58/0.52–0.60 (0.92–1.00). Leg I: trochanter 0.18–0.20/0.10–0.14 (1.43–1.80), femur 0.55–0.65/0.07– 0.09 (6.11–8.57), patella 0.26–0.34/0.06–0.08 (4.25– 4.86), tibia 0.23–0.32/0.06–0.07 (3.83–5.33), tarsus 0.58–0.72/0.05–0.07 (10.14–12.00). Leg IV: trochanter 0.22–0.27/0.14–0.17 (1.47–1.64), femoropatella 0.82– 0.95/0.21–0.23 (3.73–4.38), tibia 0.49–0.66/0.09–0.10 (5.44–7.33), basitarsus 0.25–0.30/0.07–0.08 (3.13–4.71), telotarsus 0.61–0.76/0.05–0.06 (10.17–15.00).

Remarks. Lagynochthonius apexus sp. nov. most closely resembles L. bailongtanensis in the absence of intercalary teeth, the presence of four setae on tergites I–IV and carapace without eyes or eyespots, but differs in following several characters: shorter pedipalpal chela (1.51–1.52 mm (♂), 1.39–1.62 mm (♀) compared to 1.85– 2.22 mm (♂), 1.94–2.03 mm (♀) in L. bailongtanensis ) and shorter pedipalpal femur (1.09 mm (♂), 1.00– 1.21 mm (♀) compared to 1.30–1.58 mm (♂), 1.35–1.56 mm (♀) in L. bailongtanensis ) and carapace (0.54–0.56 mm (♂), 0.48–0.58 mm (♀) compared to 0.66–0.72 mm (♂), 0.59–0.68 mm (♀) in L. bailongtanensis ) ( Li et al. 2019).

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

Figures

FIGURE 3. Lagynochthonius apexus sp. nov., A. Holotype male (dorsal view); B. Paratype female (dorsal view).

FIGURE 4. Lagynochthonius apexus sp. nov., holotype male (A–F), paratype female (G): A. Left chela (lateral view); B. Left chela (dorsal view); C. Left chelicera (dorsal view); D. Carapace (dorsal view); E. Left pedipalp (minus chela, dorsal view); F. Male genital area (ventral view); G. Female genital area (ventral view).

FIGURE 5. Lagynochthonius apexus sp. nov., holotype male: A. Carapace (dorsal view); B. Left chelicera (dorsal view), with details of teeth; C. Rallum; D. Coxal spines on coxae II (ventral view); E. Left pedipalp (minus chela, dorsal view).

FIGURE 6. Lagynochthonius apexus sp. nov., holotype male: A. Left chela (lateral view), with details of teeth and trichobothrial pattern; B. Left chela (dorsal view); C. Leg I (lateral view); D. Leg IV (lateral view).