Tyrannochthonius planus Hou & Feng & Zhang 2023, sp. nov.
Creators: name: Hou, Yanmeng
name: Feng, Zegang
name: Zhang, Feng
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Pseudoscorpiones
Chthoniidae
Tyrannochthonius
Tyrannochthonius planus

description: Tyrannochthonius planus sp. nov. ‹ṬËƟṁae›
Figs 102–106
Type material. Holotype ♂ (Ps.- MHBU-GZC190801-01 - 01): China, Guizhou Province, Sandu County, Zhonghe Town, Sandong Village, Yanggong Cave, under the stones in the deep zone (Temperature: 13°C, Humidity: 90%) [25°42′48.06″N, 107°56′00.66″E], 800 m a.s.l., 1 August 2019, Zegang Feng, Zhaoyi Li & Chen Zhang leg. Paratypes: 1 ♂ (Ps.- MHBU-GZC190801-01 - 02), 2 ♀ (Ps.- MSWU-GZC190801-01 - 03 & GZC190801-01 - 04), all with the same data as the holotype.
Etymology. The specific name is derived from the Latin word “ planus ”, meaning flat, which refers to the relatively straight anterior margin of the carapace.
Diagnosis (J ♀). Moderately sized troglomorphic species with elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated and relatively straight, without epistome; posterior margin of carapace with 2 setae; tergites II–VIII each with 4 setae. Pedipalps slender, femur 7.36–7.38 (♂), 6.79– 7.29 (♀) times longer than broad; chela 8.11–8.38 (♂), 7.68–7.82 (♀) times longer than broad; both chelal fingers without intercalary teeth, movable chelal finger teeth smaller and denser than fixed chelal finger teeth.
Description. Males (holotype and paratype) (Figs 103A, 104A–F, 105, 106).
Colour: generally pale yellow, chelicerae, pedipalps and tergites slightly darker, soft parts pale.
Cephalothorax (Figs 104C, 105A): carapace 0.98–1.00 times longer than broad, gently narrowed posteriorly; surface smooth, without furrows; no traces of eyes; anterior margin slightly serrate; without epistome; 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, the second situated exterior 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 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. 105C); intercoxal tubercle absent; without sub-oral seta.
Chelicera (Figs 104D, 105B): large, about as long as carapace, 2.45–2.48 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 12–13 teeth, distal one largest; movable finger with 11–13 retrorse contiguous small teeth; galea represented by a very slight bump on movable finger (Fig. 105B). Serrula exterior with 17–19 and serrula interior with 13–14 blades. Rallum with 7 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. 105E).
Pedipalp (Figs 104A, B, E, 105D, 106A, B): long and slender, trochanter 1.47–1.67, femur 7.36–7.38, patella 2.29–2.33, chela 8.11–8.38, hand 2.89–3.00 times longer than broad; femur 2.94–3.00 times longer than patella; movable chelal finger 1.75 times longer than hand and 0.62–0.63 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissure present on patella (Figs 104E, 105D). Chelal palm not constricted towards fingers, apodeme complex of movable chelal finger only slightly sclerotized, with weak granulation dorsally at base of fixed chelal finger. 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 nearly 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 b and proximal to est (Fig. 106A). 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: fixed chelal finger with 20–21 macrodenticles, slightly retrorse, long and pointed; movable chelal finger with 25–26 macrodenticles (smaller and denser than teeth on fixed chelal finger), retrorse and pointed (Fig. 106A). Chelal fingers straight in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand (Figs 104B, 106B).
Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 2–3: 4: 4: 4: 4: 4: 4: 4: 4: 4: T2T: 0. Sternal chaetotaxy III–XII: 12–13: 11–12: 8: 7: 8: 9: 9: 9: 0: 2. Anterior genital operculum with 10–11 setae, genital opening slit-like, with 15–18 marginal setae on each side, 42–45 in total (Fig. 104F).
Legs (Fig. 106C, D): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.81–1.94 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.21–2.24 times longer than tibia. Femoropatella of leg IV 4.05–4.32 times longer than deep; tibia 6.20–6.33 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 3.86–4.29 times longer than deep (TS= 0.26–0.27), tarsus 11.50–14.40 times longer than deep and 2.40–2.56 times longer than metatarsus (TS= 0.29). Arolium slightly shorter than the claws, not divided; claws simple.
Adult females (paratypes) (Figs 103B, 104G). Mostly same as males, but a little larger; with the same chaetotaxy of coxae as males; tergal chaetotaxy I–XII: 2–4: 4: 4: 4: 4: 4: 4: 4: 4–5: 4: T2T: 0; sternal chaetotaxy IV–XII: 11: 8–10: 9: 9: 9: 8–10: 8–9: 0: 2; anterior genital operculum with 9–10 setae, posterior margin with 12 marginal setae, 21–22 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 3.63–4.00 times longer than deep (TS= 0.25–0.31), tarsus 11.00–12.17 times longer than deep and 2.36–2.52 times longer than metatarsus (TS= 0.29).
Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 1.81–1.94. Pedipalps: trochanter 0.25/0.15–0.17 (1.47–1.67), femur 0.96–1.03/0.13–0.14 (7.36–7.38), patella 0.32–0.35/0.14–0.15 (2.29–2.33), chela 1.34–1.46/0.16–0.18 (8.11–8.38), hand 0.48–0.52/0.16–0.18 (2.89– 3.00), movable chelal finger length 0.84–0.91. Chelicera 0.49–0.52/0.20–0.21 (2.45–2.48), movable finger length 0.27–0.29. Carapace 0.46–0.49/0.47–0.49 (0.98–1.00). Leg I: trochanter 0.16/0.12–0.14 (1.14–1.33), femur 0.56– 0.62/0.07–0.08 (7.75–8.00), patella 0.31–0.32/0.06–0.07 (4.57–5.17), tibia 0.25–0.29/0.06 (4.17–4.83), tarsus 0.56– 0.64/0.05 (11.20–12.80). Leg IV: trochanter 0.21–0.24/0.13–0.14 (1.62–1.71), femoropatella 0.82–0.89/0.19–0.22 (4.05–4.32), tibia 0.57–0.62/0.09–0.10 (6.20–6.33), metatarsus 0.27–0.30/0.07 (3.86–4.29), tarsus 0.69–0.72/0.05– 0.06 (11.50–14.40).
Females: body length 1.94–2.01. Pedipalps: trochanter 0.22–0.27/0.14–0.15 (1.57–1.80), femur 0.95–1.02/0.14 (6.79–7.29), patella 0.33–0.37/0.15 (2.20–2.47), chela 1.33–1.46/0.17–0.19 (7.68–7.82), hand 0.48–0.53/0.17– 0.19 (2.79–2.82), movable chelal finger length 0.82–0.89. Chelicera 0.50–0.53/0.21–0.23 (2.30–2.38), movable finger length 0.27–0.30. Carapace 0.49–0.53/0.47–0.49 (1.04–1.08). Leg I: trochanter 0.16/0.14 (1.14), femur 0.58–0.61/0.07–0.08 (7.63–8.29), patella 0.31–0.32/0.07 (4.43–4.57), tibia 0.27–0.28/0.05–0.06 (4.50–5.60), tarsus 0.59–0.66/0.05–0.06 (11.00–11.80). Leg IV: trochanter 0.22–0.25/0.14–0.15 (1.57–1.67), femoropatella 0.82– 0.88/0.20–0.21 (4.10–4.19), tibia 0.59–0.62/0.09 (6.56–6.89), metatarsus 0.28–0.29/0.07–0.08 (3.63–4.00), tarsus 0.66–0.73/0.06 (11.00–12.17).
Remarks. Tyrannochthonius planus sp. nov. is similar to T. pictus sp. nov. in lacking an epistome on the carapace as well as intercalary teeth on both chelal fingers, but differs by having fewer teeth on both chelal fingers (fixed chelal finger with 20–21 vs. 30–32 teeth; movable chelal finger with 25–26 vs. 40–43 teeth), the trait of the teeth at movable chelal fingertip (distinctly retrorse vs. slightly retrorse) and the number of blades of rallum (7 vs. 8).
Tyrannochthonius planus sp. nov. can be distinguished from T. akaelus, T. antridraconis, T. chixing, T. ganshuanensis and T. zhai by lacking intercalary teeth on the fixed chelal finger, from T. harveyi by the number of setae at the anterior margin of the carapace (6 vs. 4) and on tergites II–III (4 vs. 2), the presence of a slender palp (chela 8.11–8.38 (♂), 7.68–7.82 (♀) times vs. 7.50 (♂), 7.22 (♀) times longer than board, length min. 1.33 mm vs. max. 1.30 mm; palpal femur 7.36–7.38 (♂), 6.79–7.29 (♀) times vs. 6.29 (♂), 5.80 (♀) times longer than board, length min. 0.95 mm vs. max. 0.88 mm) (Mahnert 2009; Gao et al. 2018, 2020).
Distribution. Known only from the type locality.
description: Published as part of Hou, Yanmeng, Feng, Zegang & Zhang, Feng, 2023, Diversity of cave-dwelling pseudoscorpions from Guizhou in China, with the description of twenty-four new species of the genus Tyrannochthonius (Pseudoscorpiones, Chthoniidae), pp. 1-158 in Zootaxa 5262 (1) on pages 124-130, DOI: 10.11646/zootaxa.5262.1.1, http://zenodo.org/record/7795161