Lagynochthonius retrorsus, Hou & Gao & Zhang, 2022

Hou, Yanmeng, Gao, Zhizhong & Zhang, Feng, 2022, Diversity of cave-dwelling pseudoscorpions from eastern Yunnan in China, with the description of eleven new species of the genus Lagynochthonius (Pseudoscorpiones, Chthoniidae), Zootaxa 5198 (1), pp. 1-65 : 28-33

publication ID	https://doi.org/ 10.11646/zootaxa.5198.1.1
publication LSID	lsid:zoobank.org:pub:019FE488-4263-4BC2-8606-446E599E226A
DOI	https://doi.org/10.5281/zenodo.7251614
persistent identifier	https://treatment.plazi.org/id/1B94E768-4328-4051-8DD5-C282EBD0510E
taxon LSID	lsid:zoobank.org:act:1B94E768-4328-4051-8DD5-C282EBD0510E
treatment provided by	Plazi
scientific name	Lagynochthonius retrorsus
status	sp. nov.

Treatment

Lagynochthonius retrorsus sp. nov. (ẁffiIJ伪oi)

Figs 19–22 View FIGURE 19 View FIGURE20 View FIGURE 21 View FIGURE 22

Type material. Holotype ♂ (Ps.- MHBU-HBUARA#2021-42101 ): China, Yunnan Province, Daguan County, Tianxing Town, Xingfu Village , Qinglong Cave , under stones within 100–150 m from the cave entrance [27°43′19.21″N, 103°59′48.86″E], 816 m a.s.l., 3 October 2021, Zegang Feng, Yanmeng Hou, Lu Zhang & Liu Fu leg. GoogleMaps Paratypes: 2 ♂ (Ps.- MHBU-HBUARA#2021-42102 & HBUARA#2021-42103) , 4 ♀ (Ps.- MSWU-HBUARA#2021-42104 - HBUARA#2021-42107), all with the same data as the holotype GoogleMaps .

Etymology. The specific name is derived from the Latin word “ retrorsus ” (= retrorse) and refers to the shape of the movable chelal finger teeth.

Diagnosis (♂ ♀). Moderately sized troglomorphic species with elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated, epistome small, pointed, triangular; posterior margin of carapace with 2 setae; tergites I–IV each with 2 setae. Pedipalps slender, femur 7.86–8.29 (♂), 7.73–8.20 (♀) times longer than broad; chela 6.83–7.32 (♂), 7.04–7.13 (♀) times longer than broad; only fixed chelal finger with intercalary teeth (rounded and obtuse) and with a modified accessory tooth (td) on dorso-antiaxial face; movable chelal finger teeth markedly retrorse and contiguous; chemosensory setae (sc) present on dorsum of chelal hand; sensilla present.

Description. Males (holotype and paratypes) ( Figs 19E View FIGURE 19 , 20A View FIGURE20 , 21A–D View FIGURE 21 , 22 View FIGURE 22 ).

Colour ( Figs 19E View FIGURE 19 , 20A View FIGURE20 , 21A–D View FIGURE 21 ): generally pale yellow, chelicerae, pedipalps and tergites slightly darker, soft parts pale.

Cephalothorax ( Figs 21B View FIGURE 21 , 22A View FIGURE 22 ): carapace 1.00–1.04 times longer than broad, gently narrowed posteriorly; surface smooth, without furrows; no traces of eyes; anterior margin slightly serrate; epistome pointed and small, triangular; 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 setae of ocular row, second pair situated lateral to the sole pair of setae of posterior row. Chaetotaxy of coxae: P 3, I 3, II 3–4, III 5, IV 5; manducatory process with two acuminate distal setae, anterior seta less than 1/3 length of medial seta; apex of coxa I with small, rounded anteromedial process; coxae II with 9–10 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. 22C View FIGURE 22 ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 21C View FIGURE 21 , 22B View FIGURE 22 ): large, about as long as carapace, 2.35–2.37 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 17–19 teeth, distal one largest; movable finger with 15–17 retrorse contiguous small teeth; galea completely vestigial ( Fig. 22B View FIGURE 22 ). Serrula exterior with 22–24 and serrula interior with 13–14 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. 22D View FIGURE 22 ).

Pedipalp ( Figs 21A View FIGURE 21 , 22E–G View FIGURE 22 ): long and slender, trochanter 1.71–1.87, femur 7.86–8.29, patella 2.35, chela 6.83– 7.32, hand 2.83–2.91 times longer than broad; femur 2.75–2.90 times longer than patella; movable chelal finger 1.43–1.50 times longer than hand and 0.59–0.60 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissure present on patella ( Fig. 22E View FIGURE 22 ). Chelal palm gradually constricted towards fingers, apodeme complex of movable chelal finger strongly 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 closer to st than to b; b and t situated subdistally, t situated distal to it; est situated distal to b ( Fig. 22F View FIGURE 22 ). A tiny antiaxial lyrifissure present at base of fixed chelal finger (situated distal to ist). Both chelal fingers with a row of teeth, heterodentate, 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 28–30 macrodenticles, slightly retrorse and pointed, plus 12–13 rounded and obtuse intercalary microdenticles, and a modified accessory tooth on dorso-antiaxial face (td, slightly distal to dx), 42–43 in total; movable chelal finger with 29–30 macrodenticles (slightly smaller than teeth on fixed chelal finger), markedly retrorse, pointed and contiguous, plus 6–8 vestigial, rounded and contiguous basal teeth, 36–37 in total; two tubercles present between first and third teeth ( Fig. 22F View FIGURE 22 ). Fixed chelal finger with sensilla af 1–2 close together, near tip; movable chelal finger with 4 sensilla: am 1–2 near tip, p 2 slightly distad of sb, p 1 distad of p 2 and very close to chelal teeth ( Fig. 22F View FIGURE 22 ). Chelal fingers slightly curved in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Fig. 22G View FIGURE 22 ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 2: 2: 2: 2: 4: 4: 4: 4–5: 5: 3–4: T2T: 0, tergites VIII–IX each with an unpaired median seta. Sternal chaetotaxy III–XII: 12–14: 11–12: 7–8: 8: 8: 9: 9: 7: 0: 2. Anterior genital operculum with 10 setae, genital opening slit-like, with 11–13 marginal setae on each side, 34–36 in total ( Fig. 21E View FIGURE 21 ).

Legs ( Fig. 22H, I View FIGURE 22 ): generally typical, long and slender. Fine granulation present on anterodorsal faces of trochanter IV, femur I, IV and patella IV. Femur of leg I 1.90–2.06 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.24–2.32 times longer than tibia. Femoropatella of leg IV 3.74–3.75 times longer than deep; tibia 6.00–6.20 times longer than deep; with basal tactile setae on both tarsal segments: basitarsus 3.63 times longer than deep (TS= 0.31–0.34), telotarsus 12.50–14.00 times longer than deep and 2.41–2.59 times longer than basitarsus (TS= 0.31–0.39). Setae of leg I (trochanter to tibia) 3–4: 10–12: 10–12: 14–16, setae of leg IV (trochanter to basitarsus) 2–3: 3: 6: 9–11: 9–11. Arolium slightly shorter than the claws, not divided; claws simple.

Adult females (paratypes) ( Figs 19F View FIGURE 19 , 20B View FIGURE20 , 21E View FIGURE 21 ). Mostly same as males, but a little larger; with same chaetotaxy of coxae as males; tergal chaetotaxy I–XII: 2: 2: 2: 2: 4: 4: 4: 5: 5: 4: T2 T: 0; sternal chaetotaxy IV –XII: 11: 7–10: 10: 9: 9: 9: 8: 0: 2; anterior genital operculum with 10 setae, posterior margin with 11 marginal setae, 22 in total; leg IV with a long tactile seta on both tarsal segments: basitarsus 3.50–3.63 times longer than deep (TS= 0.34–0.36), telotarsus 12.00–13.00 times longer than deep and 2.57–2.69 times longer than basitarsus (TS= 0.36–0.38) .

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 1.94–2.04. Pedipalps: trochanter 0.28–0.29/0.15–0.17 (1.71–1.87), femur 1.10–1.16/0.14 (7.86–8.29), patella 0.40/0.17 (2.35), chela 1.57–1.61/0.22–0.23 (6.83–7.32), hand 0.64–0.65/0.22–0.23 (2.83–2.91), movable chelal finger length 0.93–0.96. Chelicera 0.61–0.64/0.26–0.27 (2.35–2.37), movable finger length 0.33–0.34. Carapace 0.57/0.55–0.57 (1.00–1.04). Leg I: trochanter 0.17–0.20/0.11–0.14 (1.43–1.55), femur 0.59–0.66/0.08 (7.38–8.25), patella 0.31–0.32/0.07 (4.43–4.57), tibia 0.28–0.29/0.05–0.06 (4.67–5.80), tarsus 0.65/0.06 (10.83). Leg IV: trochanter 0.25–0.26/0.15–0.16 (1.56–1.73), femoropatella 0.86–0.90/0.23–0.24 (3.74–3.75), tibia 0.60–0.62/0.10 (6.00–6.20), basitarsus 0.29/0.08 (3.63), telotarsus 0.70–0.75/0.05–0.06 (12.50–14.00).

Females: body length 2.04–2.12. Pedipalps: trochanter 0.28/0.15–0.17 (1.65–1.87), femur 1.16–1.23/0.15 (7.73– 8.20), patella 0.42/0.18–0.19 (2.21–2.33), chela 1.64–1.69/0.23–0.24 (7.04–7.13), hand 0.69/0.23–0.24 (2.88–3.00), movable chelal finger length 0.99–1.01. Chelicera 0.65–0.69/0.27–0.29 (2.38–2.41), movable finger length 0.35– 0.38. Carapace 0.57–0.59/0.57–0.60 (0.98–1.00). Leg I: trochanter 0.19/0.12–0.14 (1.36–1.58), femur 0.66/0.09 (7.33), patella 0.29–0.32/0.07 (4.14–4.57), tibia 0.27–0.31/0.06 (4.50–5.17), tarsus 0.61–0.69/0.06 (10.17–11.50). Leg IV: trochanter 0.25–0.27/0.14–0.17 (1.59–1.79), femoropatella 0.87–0.92/0.22–0.24 (3.83–3.95), tibia 0.60– 0.61/0.09–0.10 (6.10–6.67), basitarsus 0.28–0.29/0.08 (3.50–3.63), telotarsus 0.72–0.78/0.06 (12.00–13.00).

Remarks. Based on the key to the Chinese species of Lagynochthonius below, L. retrorsus sp. nov. is similar to L. spinulentus sp. nov., but differs by a shorter chela (e.g. chela length 1.57–1.61 vs. 2.07–2.16 mm, movable chelal finger length 0.93–0.96 vs. 1.24–1.25 mm; all in males), the shape of the chelal fingers (the intercalary teeth round and obtuse vs. small and pointed, teeth of the movable chelal finger retrorse and contiguous vs. pointed and well-spaced), and the number of setae on tergites IV (2 vs. 4).

Lagynochthonius retrorsus sp. nov. differs from L. bailongtanensis in the shape of epistome (pointed and triangular vs. rounded and obtuse), the dentation of the chelal fingers (with intercalary teeth on fixed chelal finger vs. without intercalary teeth), and the number of setae on tergites I–IV (2 vs. 3–4).

Lagynochthonius retrorsus sp. nov. can be distinguished from L. laoxueyanensis by the presence of intercalary teeth on fixed chelal finger, the number of setae on tergites III and IV (2 and 2 vs. 4 and 4, respectively), and the larger body size (body length 1.94–2.04 vs. 1.78 mm in males) ( Li et al. 2019; Hou et al. 2022).

Distribution and habitat. This species is known only from the type locality, Qinglong Cave ( Figs 1A View FIGURE 1 , 19A–D View FIGURE 19 ), which is located about 1.2 km northwest of Xingfu Village (Daguan County). This limestone cave, located at the top of a mountain and surrounded by residential areas, has one small and triangular entrance (about 1 m high and 2 m wide). A winding tunnel (approximately 190 m in length) leads to the deepest part of the cave. All specimens were collected under stones within 100–150 m from the entrance. This space range is completely dark, with an average temperature of around 13℃ and humidity over 90%.