Lagynochthonius minimus, 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 : 22-28

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.7255279
persistent identifier	https://treatment.plazi.org/id/8A6487A5-FFDB-A930-FF11-FF72FD86FBDA
treatment provided by	Plazi
scientific name	Lagynochthonius minimus
status	sp. nov.

Treatment

Lagynochthonius minimus sp. nov. (小IJ伪oi)

Figs 14–18 View FIGURE 14 View FIGURE 15 View FIGURE 16 View FIGURE 17 View FIGURE 18

Type material. Holotype ♂ (Ps.- MHBU-HBUARA#2021-44101 ): China, Yunnan Province, Xichou County, Xingjie Town, Hexin Village , Yanfen Cave , under the stones in deep zone [23°15′39.53″N, 104°33′47.49″E], 1143 m a.s.l., 15 October 2021, Zegang Feng, Yanmeng Hou, Lu Zhang & Liu Fu leg. GoogleMaps Paratypes: 3 ♂ (Ps.-MHBU-HBUARA#2021-44102-HBUARA#2021-44104), 6 ♀ (Ps.- MHBU-HBUARA#2021-44105 -HBUARA#2021- 44110), all with the same data as the holotype GoogleMaps ; 3♀ (Ps.- MSWU-HBUARA#2021-44201 -HBUARA#2021-44203), Hexin Village , Cizhu Cave, under the stones and mud in the deep craters [23°15′46.72″N, 104°34′36.21″E], 1150 m a.s.l., with the same collection date and collectors as the holotype GoogleMaps .

Etymology. The specific name is derived from the Latin word “ minimus ”, meaning small, which refers to the relative body size of this troglomorphic species.

Diagnosis (♂ ♀). Small-sized troglomorphic species with slightly elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated, epistome small and obtuse, rounded; posterior margin of carapace with 2 setae; tergites I–IV each with 4 setae. Pedipalps slender, femur 6.67–7.00 (♂), 5.90–6.10 (♀) times longer than broad; chela 6.07–6.33 (♂), 6.14–6.54 (♀) times longer than broad; both chelal fingers without intercalary teeth but with a modified accessory tooth (td) on dorso-antiaxial face of fixed chelal finger; chemosensory setae (sc) present on dorsum of chelal hand; sensilla absent.

Description. Males (holotype and paratypes) ( Figs 14G View FIGURE 14 , 16A View FIGURE 16 , 17A–D View FIGURE 17 , 18 View FIGURE 18 ).

Colour ( Figs 14G View FIGURE 14 , 16A View FIGURE 16 , 17A–D View FIGURE 17 ): generally pale yellow, chelicerae, pedipalps and tergites slightly darker, soft parts pale.

Cephalothorax ( Figs 17B View FIGURE 17 , 18A View FIGURE 18 ): carapace 1.03–1.05 times longer than broad, gently narrowed posteriorly; surface smooth, without furrows; no traces of eyes; anterior margin slightly serrate; epistome small, rounded and obtuse; 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 4, III 5–6, IV 5; manducatory process with two acuminate distal setae, anterior seta more 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 row, longer spines present in the middle of the row, becoming shorter distally and proximally and incised for about half their length ( Fig. 18C View FIGURE 18 ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 17C View FIGURE 17 , 18B View FIGURE 18 ): large, about as long as carapace, 2.11–2.19 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 10–12 teeth, distal one largest; movable finger with 9–12 retrorse contiguous small teeth; galea completely vestigial ( Fig. 18B View FIGURE 18 ). Serrula exterior with 19–20 and serrula interior with 12–13 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. 18D View FIGURE 18 ).

Pedipalp ( Figs 17A View FIGURE 17 , 18E–G View FIGURE 18 ): long and slender, trochanter 1.78–1.89, femur 6.67–7.00, patella 2.00–2.10, chela 6.07–6.33, hand 2.43–2.58 times longer than broad; femur 2.67–3.00 times longer than patella; movable chelal finger 1.47–1.48 times longer than hand and 0.59–0.61 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissure present on patella ( Fig. 18E View FIGURE 18 ). 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, b situated at same level as est approximately, t distal to b and distal to it ( Fig. 18F View FIGURE 18 ). 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 and distal of the row, becoming smaller and closer proximally: fixed chelal finger with 34–36 macrodenticles, slightly retrorse and pointed, without intercalary teeth but with a modified accessory tooth on dorso-antiaxial face (td, slightly distal to dx), 35–37 in total; movable chelal finger with 10–11 macrodenticles (slightly smaller than teeth on fixed chelal finger), slightly retrorse and pointed, plus 22–25 vestigial, rounded and contiguous basal teeth, 33–35 in total ( Fig. 18F View FIGURE 18 ). Sensilla absent; chelal fingers straight in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Fig. 18G View FIGURE 18 ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 4: 4: 4: 4: 4: 4–5: 4–5: 5: 4–5: 4: T2T: 0. Sternal chaetotaxy III–XII: 8–9: 9–11: 8–9: 7–9: 8–9: 7–9: 9–10: 8–9: 0: 2. Anterior genital operculum with 10 setae, genital opening slit-like, with 11–13 marginal setae on each side, 33–35 in total ( Fig. 17D View FIGURE 17 ).

Legs ( Fig. 18H, I View FIGURE 18 ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur I, IV and patella IV. Femur of leg I 1.94–2.13 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.12–2.38 times longer than tibia. Femoropatella of leg IV 2.56–2.63 times longer than deep; tibia 4.50–4.71 times longer than deep; with basal tactile setae on both tarsal segments: basitarsus 3.20–3.40 times longer than deep (TS= 0.31–0.35), telotarsus 13.33–14.67 times longer than deep and 2.50–2.59 times longer than basitarsus (TS= 0.34–0.35). Setae of leg I (trochanter to tibia) 1–2: 9–10: 5–6: 8, setae of leg IV (trochanter to basitarsus) 2: 3: 4–5: 9–10: 8–10. Arolium slightly shorter than the claws, not divided; claws simple.

Adult females (paratypes) ( Figs 15D View FIGURE 15 , 16B View FIGURE 16 , 17E View FIGURE 17 ). Mostly same as males, but a little larger; chaetotaxy of coxae: P 3, I 3, II 4, III 5, IV 5; tergal chaetotaxy I–XII: 4: 4: 4: 4: 4–5: 4–5: 4–5: 4–5: 5: 4: T2T: 0; sternal chaetotaxy IV–XII: 8–10: 8–9: 8–9: 7–8: 8–9: 8–9: 7–8: 0: 2; anterior genital operculum with 11–12 setae, posterior margin with 8–9 marginal setae, 20–21 in total; leg IV with a long tactile seta on both tarsal segments: basitarsus 3.40 times longer than deep (TS= 0.29–0.35), telotarsus 10.50–10.75 times longer than deep and 2.47–2.53 times longer than basitarsus (TS= 0.36–0.37).

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 0.98–1.23. Pedipalps: trochanter 0.16–0.17/0.09 (1.78–1.89), femur 0.56–0.60/0.08–0.09 (6.67–7.00), patella 0.20–0.21/0.10 (2.00–2.10), chela 0.76–0.85/0.12–0.14 (6.07–6.33), hand 0.31–0.34/0.12–0.14 (2.43– 2.58), movable chelal finger length 0.46–0.50. Chelicera 0.35–0.38/0.16–0.18 (2.11–2.19), movable finger length 0.18–0.20. Carapace 0.36–0.39/0.35–0.37 (1.03–1.05). Leg I: trochanter 0.10–0.12/0.08–0.09 (1.25–1.33), femur 0.31–0.32/0.05–0.06 (5.33–6.20), patella 0.15–0.16/0.05 (3.00–3.20), tibia 0.16–0.17/0.03 (5.33–5.67), tarsus 0.36–0.38/0.04 (9.00–9.50). Leg IV: trochanter 0.14–0.16/0.10–0.11 (1.40–1.45), femoropatella 0.46–0.50/0.18– 0.19 (2.56–2.63), tibia 0.33–0.36/0.07–0.08 (4.50–4.71), basitarsus 0.16–0.17/0.05 (3.20–3.40), telotarsus 0.40– 0.44/0.03 (13.33–14.67).

Females: body length 1.28–1.30. Pedipalps: trochanter 0.12–0.13/0.10 (1.20–1.30), femur 0.59–0.61/0.10 (5.90–6.10), patella 0.22–0.23/0.11 (2.00–2.09), chela 0.85–0.86/0.13–0.14 (6.14–6.54), hand 0.34–0.36/0.13–0.14 (2.57–2.62), movable chelal finger length 0.50–0.51. Chelicera 0.38–0.40/0.18–0.19 (2.11), movable finger length 0.20. Carapace 0.38–0.40/0.40–0.41 (0.95–0.98). Leg I: trochanter 0.10/0.08–0.09 (1.11–1.25), femur 0.34/0.06 (5.67), patella 0.18–0.19/0.05 (3.60–3.80), tibia 0.17–0.18/0.04 (4.25–4.50), tarsus 0.38–0.39/0.04 (9.50–9.75). Leg IV: trochanter 0.14–0.15/0.09–0.11 (1.36–1.56), femoropatella 0.50/0.18–0.17 (2.78–2.94), tibia 0.30–0.37/0.07– 0.08 (4.29–4.63), basitarsus 0.17/0.05 (3.40), telotarsus 0.42–0.43/0.04 (10.50–10.75).

Remarks. Lagynochthonius minimus sp. nov. is similar to L. bailongtanensis in having a small and rounded epistome and the same number of setae on tergites II–IV, but differs by a smaller body size (e.g. body length 0.98– 1.23 vs. 2.55–2.92 mm, chela 6.07–6.33 times longer than broad vs. 8.50–10.20 times, chela length 0.76–0.85 vs. 1.85–2.22 mm, carapace length 0.36–0.39 vs. 0.66–0.72 mm; all in males) and the presence of more chelal teeth.

Lagynochthonius minimus sp. nov. differs from L. laoxueyanensis in the shape of the epistome (rounded and obtuse vs. pointed and triangular), the number of setae on tergites I and II (4 and 4, respectively vs. 2 and 2, respectively), and a smaller body size (e.g. body length 0.98–1.23 vs. 1.78 mm, chela 6.07–6.33 times longer than broad vs. 7.71 times, chela length 0.76–0.85 vs. 1.62 mm, carapace length 0.36–0.39 vs. 0.59 mm; all in males).

Small body size makes this new troglomorphic species unique (e.g. body length 0.98–1.23, chela length 0.76– 0.85). Compared with the small troglomorphic Lagynochthonius species from Jamaica ( L. typhlus , body length 1.28 mm), this new species can be distinguished by the different number of setae on tergites I–III (4 vs. 2) and the different pattern of dentation on the chelal fingers (without intercalary teeth vs. with intercalary teeth on both chelal fingers) ( Muchmore 1991; Li et al. 2019; Hou et al. 2022).

Distribution and habitat. This species is known only from the type localities, Yanfen Cave ( Figs 1M View FIGURE 1 , 14A– F View FIGURE 14 ) and Cizhu Cave ( Figs 1N View FIGURE 1 , 15A–C, E View FIGURE 15 ). Yanfen Cave is located about 0.7 km west of Hexin Village (Xichou County). This limestone cave has one semicircular and artificial entrance (about 2 m high and 4 m wide), with an approximately 150 m tunnel leading to the interior of the cave, which is a large and completely dark space, covered with gravel, with temperatures around 18°C and humidity approximate 65%. All of the specimens were collected under stones in the deep zone.

Cizhu Cave is located about 0.6 km northeast of Hexin Village (Xichou County) and ca. 1.4 km northeast of Yanfen Cave. The entrance (about 1.4 m high and 0.7 m wide) is blocked by some boulders, leaving only a small gap. A descent access leads to the bottom of the cave, which is completely dark, with constant temperature and humidity (temperature around 17°C, humidity around 80%), and some deep pits formed by the collapse are visible on the ground. All of the specimens were collected under stones and mud in these deep pits. The exit is connected to a water cave, Yanzi Cave ( Fig. 15F, G View FIGURE 15 ).