Lagynochthonius xibaiensis, 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 : 48-51

Lagynochthonius xibaiensis sp. nov. (洗白IJ伪oi)

Figs 35–37

Type material. Holotype ♀ (Ps.- MHBU-YNC190810-0201 ): China, Yunnan Province, Zhenxiong County, Chishuiyuan Town, Xibai Village , Hama Cave , under a stone in deep zone [27°28′59.93″N, 104°51′20.08″E], 1792 m a.s.l., 10 August 2019, Zegang Feng, Chen Zhang leg.

Etymology. Named after the village of Xibai, 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 small, pointed, triangular; posterior margin of carapace with 2 setae; tergites I–II each with 4 setae. Pedipalps slender, femur 9.47 times longer than broad; chela 7.38 times longer than broad; both chelal fingers without intercalary teeth but fixed chelal finger with a modified accessory tooth (td) on dorso-antiaxial face; movable chelal finger teeth are distinctly more closely aligned than those of the fixed chelal finger; chemosensory setae (sc) present on dorsum of chelal hand; sensilla absent on both chelal fingers.

Description. Female (holotype), male unknown.

Colour ( Figs 35 , 36 ): generally pale yellow, chelicerae, pedipalps and tergites slightly darker, soft parts pale.

Cephalothorax ( Figs 36B , 37A ): carapace 0.97 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 2 setae flanking base; 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; 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 12 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. 37C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 36C , 37B ): large, about as long as carapace, 2.60 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 16 teeth, distal one largest; movable finger with 17 retrorse contiguous small teeth; galea represented by a very slight bump on movable finger ( Fig. 37B ). Serrula exterior with 24 and serrula interior with 14 blades. Rallum with 7 blades, the distal two longer 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. 37D ).

Pedipalp ( Figs 36A , 37E–G ): long and slender, trochanter 1.71, femur 9.47, patella 2.32, chela 7.38, hand 3.19 times longer than broad; femur 2.78 times longer than patella; movable chelal finger 1.24 times longer than hand and 0.54 times longer than chela. Setae generally long and acuminate; 2 distal lyrifissures present on patella ( Fig. 37E ). 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 at same level as it, est distal to b ( Fig. 37F ). 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 of the row, becoming smaller and closer distally and proximally, movable chelal finger teeth more closely aligned markedly: fixed chelal finger with 30 macrodenticles, slightly retrorse and pointed, without intercalary teeth but with a modified accessory tooth on dorso-antiaxial face (td, near tip) and three tubercles between second and fourth teeth; movable chelal finger with 37 macrodenticles (slightly smaller than teeth on fixed chelal finger), slightly retrorse and pointed, plus 5 vestigial, rounded and contiguous basal teeth, 42 in total ( Fig. 37F ). Sensilla absent; chelal fingers slightly curved in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Fig. 37G ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 4: 4: 3: 3: 4: 4: 4: 4: 4: 4: T2T: 0. Sternal chaetotaxy IV–XII: 11: 11: 10: 9: 9: 9: 8: 0: 2. Anterior genital operculum with 9 setae, genital opening slit-like, with 12 marginal setae on each side, 21 in total ( Fig. 36D ).

Legs ( Fig. 37H, I ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur I, IV and patella IV. Femur of leg I 1.90 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.29 times longer than tibia. Femoropatella of leg IV 5.89 times longer than deep; tibia 5.82 times longer than deep; with basal tactile setae on both tarsal segments: basitarsus 3.88 times longer than deep (TS= 0.29), telotarsus 13.83 times longer than deep and 2.68 times longer than basitarsus (TS= 0.31). Setae of leg I (trochanter to tibia) 4: 14: 9: 13, setae of leg IV (trochanter to basitarsus) 2: 3: 6: 9: 10. 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). Female: body length 2.15. Pedipalps: trochanter 0.29/0.17 (1.71), femur 1.42/0.15 (9.47), patella 0.51/0.22 (2.32), chela 1.92/0.26 (7.38), hand 0.83/0.26 (3.19), movable chelal finger length 1.03. Chelicera 0.78/0.30 (2.60), movable finger length 0.40. Carapace 0.65/0.67 (0.97). Leg I: trochanter 0.21/0.14 (1.50), femur 0.80/0.07 (11.43), patella 0.42/0.07 (6.00), tibia 0.34/0.07 (4.86), tarsus 0.78/0.06 (13.00). Leg IV: trochanter 0.30/0.16 (1.88), femoropatella 1.12/0.19 (5.89), tibia 0.64/0.11 (5.82), basitarsus 0.31/0.08 (3.88), telotarsus 0.83/0.06 (13.83).

Remarks. Male unknown. Lagynochthonius xibaiensis sp. nov. is similar to L. laoxueyanensis , but differs by the number of setae on tergites I–II (4 and 4, respectively vs. 2 and 2, respectively), and more slender pedipalps (e.g. chela length 1.65–1.66 vs. 1.92 mm, femur 9.47 times longer than broad vs. 7.8–8.36 times; all in females).

Lagynochthonius xibaiensis sp. nov. differs from L. bailongtanensis in the shape of epistome (pointed and triangular vs. rounded and obtuse), a smaller body (2.15 vs. 2.72–2.95 mm in females), and the higher number of teeth on both chelal fingers (31 vs. 19–23 on fixed chelal finger; 42 vs. 13–17 on movable chelal finger) ( Li et al. 2019; Hou et al. 2022).

Distribution and habitat. This species is only known from the type locality, Hama Cave ( Fig. 1D ; Zhang et al. 2020), which is located about 3 km southeast of Xibai Village (Zhenxiong County). This limestone cave has one oval entrance surrounded by weeds. The interior of the cave is large and extends horizontally. Water stains are visible on the ground and walls. Temperature and humidity level is missing. The specimen was collected from under a stone in the deep zone.

Figures

FIGURE 1. Distribution map of the type locality of troglomorphic Lagynochthonius species in Yunnan (China). A. L. retrorsus sp. nov. (Qinglong Cave); B. L. fengi sp. nov. (Unnamed Cave 2); C. L. xiaolinensis sp. nov. (Dayan Cave); D. L. xibaiensis sp. nov. (Hama Cave); E. L. spinulentus sp. nov. (Yingshan Cave); F. L. xinjiaoensis sp. nov. (Yueliang Cave); G. L. magnidentatus sp. nov. (Xiao Cave); H. L. bailongtanensis sp. nov. (Qianfo Cave); I. L. laoxueyanensis sp. nov. (Laoxueyan Cave); J. L. serratus sp. nov. (Unnamed Cave 3); K. L. yaowangguensis sp. nov. (Unnamed Cave 4); L. L. crassus sp. nov. (Unnamed Cave 1); M–N. L. minimus sp. nov. (M: Yanfen Cave, N: Cizhu Cave).

FIGURE 35. Lagynochthonius xibaiensis sp. nov., A. Holotype female, habitus (dorsal view); B. Live female of L. xibaiensis sp. nov., in its natural environment.

FIGURE 36. Lagynochthonius xibaiensis sp. nov., holotype female (A–D): A. Left chela (lateral view); B. Carapace (dorsal view); C. Left chelicera (dorsal view); D. Female genital area (ventral view).

FIGURE 37. Lagynochthonius xibaiensis sp. nov., holotype female:A. Carapace (dorsal view), with a detail of anterior margin; B. Left chelicera (dorsal view), with details of teeth and galea; 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 with trichobothrial pattern, finger tips and modified tooth (abbreviations explained in Materials and methods); G. Left chela (dorsal view), with details of chemosensory setae; H. Leg I (lateral view); I. Leg IV (lateral view). Scale bars: 0.25 mm (A–B, E–I); 0.10 mm (C–D).