Lagynochthonius zhijinensis, Hou & Feng & Zhang, 2023

Hou, Yanmeng, Feng, Zegang & Zhang, Feng, 2023, New cave-dwelling pseudoscorpions of the genus Lagynochthonius (Pseudoscorpiones, Chthoniidae) from Guizhou in China, Zootaxa 5309 (1), pp. 1-64 : 55-61

Lagynochthonius zhijinensis sp. nov. (ṂĤṄṁae)

Figs 44–47

Type material. Holotype ♀ (Ps.-MHBU-GZZJ-19-04-01): China, Guizhou Province, Zhijin County, Chengguan Town, Yangliu Village , Long Cave , under stones in the deep zone [26°40′45.63″N, 105°47′16.30″E], 1345 m a.s.l., 2 October 2019, Zegang Feng & Lingchen Zhao leg. Paratype: 1 ♀ (Ps.-MSWU-GZZJ-19-04-02), with the same data as the holotype .

Etymology. Named after the Zhijin County, near the type locality.

Diagnosis (♀). Moderately sized troglomorphic species with elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated, epistome pointed and small, triangular; posterior margin of carapace with two setae; tergites II–III each with two setae, tergites IV–VII each with four setae. Pedipalps slender, femur 8.47–8.53 times longer than broad; chela 7.46–7.71 times longer than broad; only fixed chelal finger with intercalary teeth and a modified accessory tooth (td) on retrolateral face; chelal fingers slightly curved in dorsal view; chemosensory setae (sc) present on dorsum of chelal hand.

Description. Females (holotype and paratype), male unknown ( Figs 45–47 ).

Colour: generally pale yellow, chelicerae, pedipalps and tergites slightly darker, soft parts pale.

Cephalothorax ( Figs 46C , 47A ): carapace 0.93–0.98 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 the 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, IV 5–6; manducatory process with two acuminate distal setae, anterior seta less than 1/2 length of medial seta; apex of coxa Ⅰ with small, rounded anteromedial process; coxae II with 11–12 terminally indented coxal spines on each side, set as an oblique and arc row, longer spines present in the middle of the row, becoming shorter distally and proximally and incised for about half their length ( Fig. 47C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 46D , 47B ): large, about as long as carapace, 2.29–2.31 times longer than broad; five setae and two 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 20–24 teeth, distal one largest; movable finger with 18–19 retrorse contiguous small teeth; galea absent ( Fig. 47B ). Serrula exterior with 20–21 blades and serrula interior with 13–15 blades. Rallum with seven 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. 47D ).

Pedipalp ( Figs 46A–B, F , 47E–G ): long and slender, trochanter 1.25–1.32, femur 8.47–8.53, patella 2.21–2.37, chela 7.46–7.71, hand 3.04–3.17 times longer than broad; femur 2.84–3.02 times longer than patella; movable chelal finger 1.42–1.45 times longer than hand and 0.58–0.59 times longer than chela. Setae generally long and acuminate; one distal lyrifissure present on patella ( Figs 46F , 47E ). Chelal palm gradually constricted towards fingers, apodeme complex of movable chelal finger strongly sclerotized, with weak granulation dorsally at base of fixed chelal finger. 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 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 situated midway between b and st; b and t situated subdistally and situated at the same level as est and it, respectively ( Fig. 47F ). A tiny retrolateral 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 teeth present in the middle of the row, becoming smaller and closer distally and proximally: fixed chelal finger with 23 macrodenticles, slightly retrorse and pointed, plus 11– 12 intercalary microdenticles, 34–35 in total; movable chelal finger with 21–22 macrodenticles (slightly smaller than teeth on fixed chelal finger), slightly retrorse and pointed, plus 7–8 vestigial, rounded and contiguous basal teeth, 28–30 in total ( Fig. 47F ). Chelal fingers slightly curved in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs 46B , 47G ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy Ⅰ–XII: 2–3: 2: 2: 4: 4: 4: 4: 5: 5: 2: T2T: 0, tergites VIII and IX each with an unpaired median seta. Sternal chaetotaxy IV–XII: 13: 9: 9–10: 8–9: 9: 9: 7–8: 0: 2. Anterior genital operculum with 9–10 setae, posterior margin with 12–14 marginal setae, 21–24 in total ( Fig. 46E ).

Legs ( Fig. 47H–I ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg Ⅰ 1.76–1.79 times longer than patella and with one lyrifissure at the base of femur; tarsus 2.48–2.56 times longer than tibia. Femoropatella of leg IV 4.12–4.13 times longer than deep; tibia 6.27–6.36 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 3.56 times longer than deep (TS = 0.28–0.34), tarsus 14.17–14.33 times longer than deep and 2.66–2.69 times longer than metatarsus (TS = 0.31–0.34). Arolium slightly shorter than the claws, not divided; claws simple.

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Females: body length 2.17–2.36. Pedipalps: trochanter 0.25/0.19–0.20 (1.25–1.32), femur 1.27–1.28/0.15 (8.47–8.53), patella 0.42–0.45/0.19 (2.21–2.37), chela 1.79–1.85/0.24 (7.46–7.71), hand 0.73–0.76/0.24 (3.04–3.17), movable chelal finger length 1.06–1.08. Chelicera 0.71–0.74/0.31–0.32 (2.29–2.31), movable finger length 0.37–0.38. Carapace 0.62–0.65/0.66–0.67 (0.93–0.98). Leg Ⅰ: trochanter 0.19–0.21/0.16 (1.19–1.31), femur 0.70–0.72/0.09 (7.78–8.00), patella 0.39–0.41/0.08–0.09 (4.56–4.88), tibia 0.31–0.32/0.06 (5.17–5.33), tarsus 0.77–0.82/0.06–0.07 (11.71– 12.83). Leg IV: trochanter 0.28–0.29/0.16–0.18 (1.61–1.75), femoropatella 0.99–1.03/0.24–0.25 (4.12–4.13), tibia 0.69–0.70/0.11 (6.27–6.36), metatarsus 0.32/0.09 (3.56), tarsus 0.85–0.86/0.06 (14.17–14.33).

Distribution. Known only from the type locality.

Key to the species of Lagynochthonius from China

1 Carapace without antero-median setae; trichobothrium sb closer to b than to st ..................................... 2

- Carapace with antero-median setae; trichobothrium sb closer to st than to b or midway between st and b ................ 3

2 Chela 7.03 (♂) times as long as broad (length 2.04 mm); epistome pointed and small, triangular............................................................................................ L. xinjiaoensis Hou, Gao & Zhang, 2022

- Chela 6.44–6.46 (♂), 5.87–6.04 (♀) times as long as broad (length 1.55–1.61 (♂), 1.69–1.76 (♀) mm); epistome small and obtuse, rounded..................................................... L. magnidentatus Hou, Gao & Zhang, 2022

3 Carapace without eyes or eyespots........................................................................ 4

- Carapace with eyes or eyespots......................................................................... 13

4 At least one chela finger with intercalary teeth.............................................................. 5

- Both chelal fingers without intercalary teeth............................................................... 21

5 Only fixed chelal finger with intercalary teeth............................................................... 6

- Both chelal fingers with intercalary teeth................................................................... 8

6 Trichobothrium sb closer to st than to b; tergite Ⅹ with four setae............................................... 7

- Trichobothrium sb situated midway between st and b; tergite Ⅹ with two setae..................... L. zhijinensis sp. nov.

7 The intercalary teeth round and obtuse; the teeth on movable chelal fingers retrorse and contiguous; chela length 1.57–1.61 (♂), 1.64–1.69 (♀) mm; movable chelal finger length 0.93–0.96 (♂), 0.99–1.01 (♀) mm.... L. retrorsus Hou, Gao & Zhang, 2022

- The intercalary teeth small and pointed; the teeth on movable chelal fingers pointed and well-spaced; chela length 2.07–2.16 (♂), 2.06–2.19 (♀) mm; movable chelal finger length 1.24–1.25 (♂), 1.20–1.26 (♀) mm.................................................................................................. L. spinulentus Hou, Gao & Zhang, 2022

8 Tergites II–III and Ⅹ each with four setae.................................................................. 9

- Tergites II–III and Ⅹ each with two setae.................................................................. 10

9 Trichobothrium sb closer to st than to b; body length 1.42 (♂), 1.59 (♀) mm; chela 6.65 (♂), 6.63 (♀) times as long as broad (length 1.33 (♂), 1.26 (♀) mm); palpal femur 7.15 (♂), 7.42 (♀) times as long as broad (length 0.93 (♂), 0.89 (♀) mm); coxae II with seven terminally indented coxal spines on each side................................. L. longedentatus sp. nov.

- Trichobothrium sb situated midway between st and b; body length 1.63 (♂), 1.81–2.20 (♀) mm; chela 8.76 (♂), 8.30–8.32 (♀) times as long as broad (length 1.84 (♂), 1.83–1.91 (♀) mm); palpal femur 10.46 (♂), 10.07–10.38 (♀) times as long as broad (length 1.36 (♂), 1.35–1.41 (♀) mm); coxae II with 9–11 terminally indented coxal spines on each side.................................................................................. L. yaowangguensis Hou, Gao & Zhang, 2022

10 Chelal fingers straight or slightly curved in dorsal view; fixed chelal finger with max. 47 teeth, movable chelal finger with max. 42 teeth............................................................................................ 11

- Chelal fingers markedly curved in dorsal view; fixed chelal finger with 58–60 teeth, movable chelal finger with 60–61 teeth.................................................................................. L. guanniuensis sp. nov.

11 Palpal femur 8.07–8.93 (♂) times as long as broad (length 1.21–1.25 mm), chela length 1.68–1.76 (♂) mm; trichobothrium sb closer to st than to b .................................................................................. 12

- Palpal femur 7.57–7.64 (♂) times as long as broad (length 1.06–1.07 mm), chela length 1.53–1.54 (♂) mm; trichobothrium sb situated midway between st and b .............................................. L. fengi Hou, Gao & Zhang, 2022

12 Carapace markedly narrowed posteriorly; chela 8.38–8.84 (♂) times as long as broad, hand 3.38–3.58 (♂) times longer than broad; proximal half of movable chelal finger without vestigial teeth; trichobothrium sb of movable chelal finger 1.22–1.24 times as far from st as from b ............................................... L. serratus Hou, Gao & Zhang, 2022

- Carapace gently narrowed posteriorly; chela 7.00 (♂) times as long as broad, hand 2.92 (♂) times longer than broad; proximal half of movable chelal finger with six vestigial teeth; trichobothrium sb of movable chelal finger 1.67 times as far from st as from b ............................................................... L. xiaolinensis Hou, Gao & Zhang, 2022

13 Troglomorphic species with a larger body size and elongate appendages: body length not less than 1.71 (♂, ♀) mm, chela length not less than 1.32 (♂, ♀) mm; without corneate eyes, only anterior pair of eyespots present.......................... 14

- Epigean species with smaller body size and without elongate appendages: body length not more than 1.60 (♂, ♀) mm, chela length not more than 1.00 (♂, ♀) mm; with corneate eyes, anterior pair of eyes well developed....................... 15

14 Chela 7.00–7.14 (♂), 6.40–6.46 (♀) times as long as broad (length 1.54–1.57 (♂), 1.55–1.60 (♀) mm); palpal femur 8.21–8.50 (♂), 7.50–7.87 (♀) times as long as broad (length 1.15–1.19 (♂), 1.18–1.20 (♀) mm); coxae II with 8–9 terminally indented coxal spines on each side................................................... L. crassus Hou, Gao & Zhang, 2022

- Chela 7.33–7.67 (♂), 6.71–6.82 (♀) times as long as broad (length 1.32–1.38 (♂), 1.41–1.50 (♀) mm); palpal femur 6.92–7.23 (♂), 6.80–7.29 (♀) times as long as broad (length 0.90–0.94 (♂), 1.02 (♀) mm); coxae II with 9–11 terminally indented coxal spines on each side.................................................................... L. latipectus sp. nov.

15 Two corneate eyes, posterior pair of eyes reduced to eyespots; tergites Ⅰ and II each with four setae................... 16

- Four corneate eyes, posterior pair of eyes well developed; tergites Ⅰ and II each with two setae................................................................................................... L. medog Zhang & Zhang, 2014

16 Carapace without epistome or with extremely indistinct epistome.............................................. 17

- Carapace with a distinct triangular epistome........................................... L. niger Hu & Zhang, 2012

17 At least one finger of chela with intercalary teeth........................................................... 18

- Both chelal fingers without intercalary teeth............................................................... 19

18 Only fixed chelal finger with intercalary teeth........................................ L. harveyi Hu & Zhang, 2014

- Both chelal fingers with intercalary teeth.............................................. L. tonkinensis ( Beier, 1951)

19 Movable chelal finger more than 1.20 (♂, ♀) times longer than hand; proximal half of movable finger with rounded vestigial teeth.............................................................................................. 20

- Movable chelal finger 1.03 (♂) times, 0.97–1.00 (♀) times longer than hand; proximal half of movable chelal finger without vestigial teeth........................................................ L. brachydigitatus Zhang & Zhang, 2014

20 Chelal hand 2.50–2.87 (♂) times, 2.39–2.75 (♀) as long as broad; trichobothrium sb of movable chelal finger two times as far from st as from b; tergites Ⅰ–VII with four setae................................... L. leptopalpus Hu & Zhang, 2012

- Chelal hand 2.00 (♂) times as long as broad; trichobothrium sb of movable chelal finger 1.5 times as far from st as from b; only the tergites Ⅰ–II with four setae......................................................... L. sinensis (Beier, 1967)

21 Tergites Ⅰ–II each with two setae........................................................................ 22

- Tergites Ⅰ–II each with three or four setae................................................................. 25

22 Carapace with a round and obtuse epistome; body length max. 1.83 mm, chelal length max. 1.11 mm .................. 23

- Carapace with a distinct triangular epistome; body length min. 1.85 mm, chelal length min. 1.51 mm .................. 24

23 Palpal femur 6.45–6.80 (♀) times as long as broad; chelal finger 1.48–1.50 (♀) times longer than hand; tergite Ⅴ with 5–6 setae; anterior genital operculum with 12 setae; trichobothrium ist situated distal to st ................... L. tuoluoensis sp. nov.

- Palpal femur 5.43–5.75 (♀) times as long as broad; chelal finger 1.55–1.56 (♀) times longer than hand; tergite Ⅴ with four setae; anterior genital operculum with ten setae; trichobothrium ist situated proximal st .............. L. maanensis sp. nov .

24 Tergite Ⅹ with two setae; body length min. 2.00 (♂), 2.17 (♀) mm, chelal length min. 1.79 (♂), 1.84 (♀) mm, palpal femur min. 1.25 (♂), 1.30 (♀) mm; coxae II with 13–15 terminally indented coxal spines on each side........... L. nigriculus sp. nov.

- Tergite Ⅹ with four setae; body length max. 1.78 (♂), 2.05 (♀) mm, chelal length max. 1.62 (♂), 1.66 (♀) mm, palpal femur max. 1.11 (♂), 1.17 (♀) mm; coxae II with nine terminally indented coxal spines on each side.......................................................................................... L. laoxueyanensis Hou, Gao & Zhang, 2022

25 Carapace with a distinct triangular epistome............................................................... 26

- Carapace with a round and obtuse epistome............................................................... 27

26 Chelal finger 1.51 (♀) times longer than hand; trichobothrium sb situated midway between st and b; coxae II with ten terminally indented coxal spines on each side; rallum with nine blades; movable chelal finger with 27–29 teeth... L. biyunensis sp. nov.

- Chelal finger 1.24 (♀) times longer than hand; trichobothrium sb closer to st than to b; coxae II with 12 terminally indented coxal spines on each side; rallum with seven blades; movable chelal finger with 42 teeth.................................................................................................. L. xibaiensis Hou, Gao and Zhang, 2022

27 Smaller: body length max. 1.23 (♂), 1.47 (♀) mm; chela length max. 0.85 (♂), 0.97 (♀) mm; palpal femur length max. 0.60 (♂), 0.67 (♀) mm.................................................................................... 28

- Larger: body length min. 1.59 (♂), 1.64 (♀) mm; chela length min. 1.03 (♂), 1.12 (♀) mm; palpal femur length min. 0.74 (♂), 0.80 (♀) mm........................................................................................ 29

28 Fixed chelal finger with 24–25 teeth; trichobothrium sb situated midway between st and b; rallum with nine blades............................................................................................ L. xiaoensis sp. nov.

- Fixed chelal finger with 35–37 teeth; trichobothrium sb closer to st than to b; rallum with eight blades........................................................................................ L. minimus Hou, Gao and Zhang, 2022

29 Larger: body length min. 1.76 (♂), 1.93 (♀) mm; chela length min. 1.26 (♂), 1.38 (♀) mm; palpal femur length min. 0.90 (♂), 0.99 (♀) mm........................................................................................ 30

- Smaller: body length max. 1.66 (♂), 1.73 (♀) mm; chela length max. 1.11(♂), 1.14 (♀) mm; palpal femur length max. 0.79 (♂), 0.80 (♀) mm...................................................................... L. mawangensis sp. nov.

30 Trichobothrium sb situated midway between st and b; body length 1.76–1.95 (♂), 1.93 (♀) mm, chela 6.63–6.95 (♂), 5.75 (♀) times longer than broad (length 1.26–1.32 (♂), 1.38 (♀) mm)................................ L. longyanensis sp. nov.

- Trichobothrium sb closer to st than to b; body length 2.55–2.92 (♂), 2.72–2.95 (♀) mm, chela 8.50–10.20 (♂) times longer than broad (length 1.85–2.22 (♂), 1.94–2.03 (♀) mm).............................. L. bailongtanensis Li, Liu & Shi, 2019

Figures

FIGURE 44. Long Cave, type locality of Lagynochthonius zhijinensis sp. nov., A. Entrance; B. Inside the cave entrance; C. A narrow tunnel to the interior of the cave; D. Area where L. zhijinensis sp. nov. specimens were collected.

FIGURE 45. Lagynochthonius zhijinensis sp. nov., holotype female, habitus (dorsal view).

FIGURE 46. Lagynochthonius zhijinensis sp. nov., holotype female: A. Left chela (lateral view); B. Left chela (dorsal view); C. Carapace (dorsal view); D. Left chelicera (dorsal view); E. Female genital area (ventral view); F. Left pedipalp (minus chela, dorsal view).

FIGURE 47. Lagynochthonius zhijinensis sp. nov., holotype female:A. Carapace (dorsal view); B. Left chelicera (dorsal view), with details of teeth; C. Coxal spines on coxae II (ventral view); D. Rallum; E. Left pedipalp (minus chela, dorsal view); F. Left chela (lateral view), with details of teeth and trichobothrial pattern; G. Left chela (dorsal view); H. Leg Ⅰ (lateral view); I. Leg IV (lateral view). Scale bars: 0.20 mm (A–B, E–I); 0.10 mm (C–D).