Tyrannochthonius acutus 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 acutus

description: Tyrannochthonius acutus sp. nov. ‹ḰẊƟṁae›
Figs 2–6
Type material. Holotype ♂ (Ps.- MHBU-GZKL-19-23-01): China, Guizhou Province, Kaili City, Zhouxi Town, Gazuida Cave, under stones within 20–200 m from the cave entrance (Temperature: 16°C, Humidity: 70%) [26°28′58.77″N, 107°55′38.24″E], 716 m a.s.l., 12 October 2019, Zegang Feng & Lingchen Zhao leg. Paratypes: 2 ♂ (Ps.- MHBU-GZKL-19-23-02 & GZKL-19-23-03), 4 ♀ (Ps.- MSWU-GZKL-19-23-04 – GZKL-19-23-07), all with the same data as the holotype.
Etymology. The specific name is derived from the Latin word “ acutus ”, meaning acute, which refers to the distinctly sharp epistome.
Diagnosis (J ♀). Moderately sized troglomorphic species with elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated, epistome distinctly pointed, triangular; posterior margin of carapace with 2 setae; tergites II–VI each with 4 setae. Pedipalps slender, femur 6.58–6.67 (♂), 6.63–6.94 (♀) times longer than broad; chela 7.29–7.65 (♂), 7.38–7.79 (♀) times longer than broad; both chelal fingers with intercalary teeth, movable chelal finger teeth distinctly more retrorse than those of the fixed chelal finger.
Description. Males (holotype and paratypes) (Figs 3A, 4A–F, 5, 6).
Colour: generally pale yellow, chelicerae, pedipalps and tergites slightly darker, soft parts pale.
Cephalothorax (Figs 4C, 5A, C): carapace 0.96–1.00 times longer than broad, gently narrowed posteriorly; surface smooth, without furrows; no traces of eyes; anterior margin slightly serrate; epistome distinctly pointed, 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, 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 10–11 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. 5C); intercoxal tubercle absent; without sub-oral seta.
Chelicera (Figs 4D, 5B): large, about as long as carapace, 2.42 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 20–23 teeth, fourth one largest; movable finger with 24–26 retrorse contiguous small teeth; galea completely vestigial. Serrula exterior with 24–26 and serrula interior with 14–15 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. 5E).
Pedipalp (Figs 4A, B, E, 5D, 6A, B): long and slender, trochanter 1.10–1.20, femur 6.58–6.67, patella 2.27– 2.35, chela 7.29–7.65, hand 2.46–2.57 times longer than broad; femur 2.50–2.55 times longer than patella; movable chelal finger 1.92–1.93 times longer than hand and 0.65 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissures present on patella (Figs 4E, 5D). 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 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 an 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 est and distal to b (Fig. 6A). 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 44–46 macrodenticles, long and pointed, plus 13– 14 intercalary microdenticles, 57–60 in total; movable chelal finger with 43–46 macrodenticles (markedly smaller than teeth on fixed chelal finger), markedly retrorse and pointed, plus 15– 16 intercalary microdenticles, 58–62 in total (Fig. 6A). Chelal fingers slightly curved in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand (Figs 4B, 6B).
Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 4–5: 4: 4: 4: 4: 4: 4: 4–5: 4–5: 4: T2T: 0, tergites VII–IX each with an unpaired median seta. Sternal chaetotaxy III–XII: 12–13: 12–13: 8–9: 7–8: 7: 7: 7–8: 7–8: 0: 2. Anterior genital operculum with 9–12 setae, genital opening slit-like, with 18–20 marginal setae on each side, 47–50 in total (Fig. 4F).
Legs (Fig. 6C, D): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.85–1.92 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.26–2.59 times longer than tibia. Femoropatella of leg IV 3.53–3.81 times longer than deep; tibia 6.08–6.45 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 3.67–4.11 times longer than deep (TS= 0.30), tarsus 14.17–15.50 times longer than deep and 2.51–2.58 times longer than metatarsus (TS= 0.33–0.36). Arolium slightly shorter than the claws, not divided; claws simple.
Adult females (paratypes) (Figs 3B, 4G). Mostly same as males, but a little larger; with same coxal chaetotaxy as males; tergal chaetotaxy I–XII: 4: 4: 4: 4: 4: 4: 4–5: 5: 5: 4: T2 T: 0; sternal chaetotaxy IV–XII: 11–12: 8: 7–8: 7: 7–8: 8–9: 7: 0: 2; anterior genital operculum with 10–11 setae, posterior margin with 11–12 marginal setae, 22 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 3.56–3.78 times longer than deep (TS= 0.31– 0.32), tarsus 13.67–14.67 times longer than deep and 2.56–2.59 times longer than metatarsus (TS= 0.33–0.35).
Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 2.07–2.13. Pedipalps: trochanter 0.22–0.24/0.20 (1.10–1.20), femur 1.20–1.25/0.18–0.19 (6.58–6.67), patella 0.47–0.50/0.20–0.22 (2.27–2.35), chela 1.75–1.76/0.23–0.24 (7.29–7.65), hand 0.59/0.23–0.24 (2.46–2.57), movable chelal finger length 1.13–1.14. Chelicera 0.75–0.80/0.31–0.33 (2.42), movable finger length 0.40–0.42. Carapace 0.65–0.68/0.68 (0.96–1.00). Leg I: trochanter 0.20–0.21/0.18 (1.11–1.17), femur 0.72–0.75/0.10 (7.20–7.50), patella 0.39/0.09 (4.33), tibia 0.32–0.35/0.07 (4.57–5.00), tarsus 0.79–0.83/0.06 (13.17–13.83). Leg IV: trochanter 0.28–0.32/0.18–0.20 (1.56–1.60), femoropatella 1.03–1.13/0.27–0.32 (3.53–3.81), tibia 0.71–0.79/0.11–0.13 (6.08–6.45), metatarsus 0.33–0.37/0.09 (3.67–4.11), tarsus 0.85–0.93/0.06 (14.17–15.50).
Females: body length 2.16–2.29. Pedipalps: trochanter 0.27/0.20–0.22 (1.23–1.35), femur 1.25–1.26/0.18–0.19 (6.63–6.94), patella 0.50/0.22–0.23 (2.17–2.27), chela 1.77–1.87/0.24 (7.38–7.79), hand 0.59–0.62/0.24 (2.46– 2.58), movable chelal finger length 1.16–1.23. Chelicera 0.82–0.86/0.35–0.36 (2.34–2.39), movable finger length 0.44–0.46. Carapace 0.67–0.69/0.72–0.77 (0.90–0.93). Leg I: trochanter 0.17–0.20/0.16–0.18 (1.06–1.11), femur 0.69–0.72/0.09–0.10 (7.20–7.67), patella 0.37–0.39/0.08–0.09 (4.33–4.63), tibia 0.33–0.34/0.07 (4.71–4.86), tarsus 0.78–0.81/0.06 (13.00–13.50). Leg IV: trochanter 0.26–0.28/0.17 (1.53–1.65), femoropatella 0.99–1.03/0.27 (3.67–3.81), tibia 0.70–0.72/0.11–0.12 (6.00–6.36), metatarsus 0.32–0.34/0.09 (3.56–3.78), tarsus 0.82–0.88/0.06 (13.67–14.67).
Remarks. Tyrannochthonius acutus sp. nov. is similar to T. hispidus sp. nov. in having intercalary teeth on both chelal fingers and a pointed, triangular epistome, but differs by a larger body size (body length 2.07–2.13 (J), 2.16–2.29 (♀) vs. 1.56–1.78 (J), 1.77–1.99 (♀) mm, chela 7.29–7.65 (J), 7.38–7.79 (♀) vs. 6.68–6.72 (J), 6.20–6.79 (♀) times longer than board), the number of blades of rallum (7 vs. 6) and the presence of more fixed chelal finger teeth (57–60 vs. 42–43).
Tyrannochthonius acutus sp. nov. can be distinguished from T. chixing, T. harveyi and T. zhai by the number of setae at the anterior margin of the carapace (6 vs. 4) and the presence of intercalary teeth on both chelal fingers, from T. akaelus and T. ganshuanensis by the number of setae on tergite II (4 vs. 2) and from T. antridraconis by the presence of more chelal teeth (57–60 vs. 33–36 teeth on the fixed chelal finger; 58–62 vs. 30–36 teeth on the movable chelal finger) (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 7-13, DOI: 10.11646/zootaxa.5262.1.1, http://zenodo.org/record/7795161