Tyrannochthonius umidus, Hou & Feng & Zhang, 2023

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), Zootaxa 5262 (1), pp. 1-158 : 142-144

Tyrannochthonius umidus sp. nov. ‹AEÎƟṁae›

Figs 116–120

Type material. Holotype ♂ (Ps.-MHBU-GZGY-20-06-01): China, Guizhou Province, Wudang District, Shuitian Town, Lizi Village , Da Cave , under the stones in the deep zone (Temperature: 14°C, Humidity: 95%) [26°42′54.76″N, 106°49′1.46″E], 1334 m a.s.l., 17 August 2020, Zegang Feng, Hongru Xu & Yanmeng Hou leg. Paratypes: 13 ♂ (Ps.-MHBU-GZGY-20-06-02–GZGY-20-06-14), 7 ♀ (Ps.-MSWU-GZGY-20-06-15–GZGY-20-06-21), all with the same data as the holotype .

Etymology. The specific name is derived from the Latin word “ umidus ”, meaning humid, which refers to the species that live in an extremely humid environment.

Diagnosis (J ♀). Moderately sized troglomorphic species with elongated appendages; carapace without eyes or eyespots; anterior margin of carapace thin, finely denticulated, without epistome; posterior margin of carapace with 2 setae; tergites I–III each with 2 setae. Pedipalps slender, femur 7.86–7.93 (♂), 7.60–8.23 (♀) times longer than broad; chela 8.44–9.06 (♂), 7.75–8.33 (♀) times longer than broad; both chelal fingers without intercalary teeth, movable chelal finger teeth markedly smaller than fixed chelal finger teeth.

Description. Males (holotype and paratypes) ( Figs 116E , 117A , 118A–F , 119 , 120 ).

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

Cephalothorax ( Figs 118C , 119A ): carapace 1.13–1.14 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 more than 1/2 length of medial seta; apex of coxa I with small, rounded anteromedial process; coxae II with 12–13 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. 119C ); intercoxal tubercle absent; without sub-oral seta.

Chelicera ( Figs 118D , 119B ): large, about as long as carapace, 2.26–2.41 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 9–11 teeth, distal one largest; movable finger with 13–16 retrorse contiguous small teeth; galea completely vestigial ( Fig. 119B ). Serrula exterior with 20–22 and serrula interior with 12–14 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. 119E ).

Pedipalp ( Figs 118A, B, E , 119D , 120A, B ): long and slender, trochanter 1.25–1.31, femur 7.86–7.93, patella 2.80, chela 8.44–9.06, hand 2.94–3.12 times longer than broad; femur 2.62–2.64 times longer than patella; movable chelal finger 1.79–1.83 times longer than hand and 0.63 times longer than chela. Setae generally long and acuminate; 1 distal lyrifissure present on patella ( Figs 118E , 119D ). 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 b than to st; b and t situated subdistally, t situated at same level as est and distal to b ( Fig. 120A ). 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 26–29 macrodenticles, slightly retrorse, long and pointed; movable chelal finger with 39–42 macrodenticles (markedly smaller than teeth on fixed chelal finger), continuous and retrorse, almost prostrate ( Fig. 120A ). Chelal fingers straight in dorsal view; microsetae (chemosensory setae) present on dorsum of chelal hand ( Figs 118B , 120B ).

Opisthosoma: generally typical, pleural membrane finely granulated. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I–XII: 2: 2: 2: 1–2: 4: 3–4: 4: 4: 4: 2: T2T: 0. Sternal chaetotaxy III–XII: 11–12: 11–12: 8: 7: 7–8: 7: 9: 8–9: 0: 2. Anterior genital operculum with 9 setae, genital opening slit-like, with 13–16 marginal setae on each side, 36–39 in total ( Fig. 118F ).

Legs ( Fig. 120C, D ): generally typical, long and slender. Fine granulation present on anterodorsal faces of femur IV and patella IV. Femur of leg I 1.88–2.06 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.41–2.52 times longer than tibia. Femoropatella of leg IV 4.36–4.60 times longer than deep; tibia 6.00–6.30 times longer than deep; with basal tactile setae on both tarsal segments: metatarsus 4.29 times longer than deep (TS= 0.30), tarsus 16.00–16.40 times longer than deep and 2.67–2.73 times longer than metatarsus (TS= 0.26–0.29). Arolium slightly shorter than the claws, not divided; claws simple.

Adult females (paratypes) ( Figs 117B , 118G ). Mostly same as males, but a little larger; with same chaetotaxy of coxae as males; tergal chaetotaxy I–XII: 2: 2: 2: 2: 4: 4: 4: 4: 4: 2: T2 T: 0; sternal chaetotaxy IV–XII: 10–12: 8–9: 7: 7–9: 8–9: 9: 8: 0: 2; anterior genital operculum with 10–11 setae, posterior margin with 10–12 marginal setae, 21–22 in total; leg IV with a long tactile seta on both tarsal segments: metatarsus 3.75–3.86 times longer than deep (TS= 0.30–0.33), tarsus 14.80–15.40 times longer than deep and 2.57–2.74 times longer than metatarsus (TS= 0.25–0.31) .

Dimensions (length/breadth or, in the case of the legs, length/depth in mm; ratios in parentheses). Males: body length 2.00–2.04. Pedipalps: trochanter 0.20–0.21/0.16 (1.25–1.31), femur 1.10–1.11/0.14 (7.86–7.93), patella 0.42/0.15 (2.80), chela 1.52–1.54/0.17–0.18 (8.44–9.06), hand 0.53/0.17–0.18 (2.94–3.12), movable chelal finger length 0.95–0.97. Chelicera 0.52–0.53/0.22–0.23 (2.26–2.41), movable finger length 0.27–0.29. Carapace 0.54– 0.57/0.48–0.50 (1.13–1.14). Leg I: trochanter 0.15–0.17/0.15 (1.00–1.13), femur 0.64–0.66/0.08 (8.00–8.25), patella 0.32–0.34/0.07 (4.57–4.86), tibia 0.27–0.29/0.05–0.06 (4.83–5.40), tarsus 0.68–0.70/0.05 (13.60–14.00). Leg IV: trochanter 0.23–0.25/0.15–0.16 (1.44–1.67), femoropatella 0.92–0.96/0.20–0.22 (4.36–4.60), tibia 0.60–0.63/0.10 (6.00–6.30), metatarsus 0.30/0.07 (4.29), tarsus 0.80–0.82/0.05 (16.00–16.40).

Females: body length 1.82–2.12. Pedipalps: trochanter 0.20/0.16–0.17 (1.18–1.25), femur 1.07–1.14/0.13–0.15 (7.60–8.23), patella 0.40–0.44/0.15–0.16 (2.67–2.75), chela 1.50–1.55/0.18–0.20 (7.75–8.33), hand 0.51–0.56/0.18– 0.20 (2.80–2.83), movable chelal finger length 0.97–0.98. Chelicera 0.51–0.54/0.21–0.23 (2.35–2.43), movable finger length 0.28–0.30. Carapace 0.52–0.55/0.48–0.51 (1.08). Leg I: trochanter 0.14–0.16/0.13–0.14 (1.08–1.14), femur 0.61–0.67/0.08 (7.63–8.38), patella 0.32–0.33/0.07 (4.57–4.71), tibia 0.26–0.29/0.06 (4.33–4.83), tarsus 0.69–0.70/0.06 (11.50–11.67). Leg IV: trochanter 0.20–0.22/0.14–0.15 (1.43–1.47), femoropatella 0.90–0.95/0.17– 0.18 (5.00–5.59), tibia 0.59–0.64/0.09–0.10 (6.40–6.56), metatarsus 0.27–0.30/0.07–0.08 (3.75–3.86), tarsus 0.74– 0.77/0.05 (14.80–15.40).

Remarks. Tyrannochthonius umidus sp. nov. is similar to T. pinguis sp. nov. in lacking an epistome on the carapace as well as intercalary teeth on both chelal fingers, but differs by the presence of more slender chela (chela 8.44–9.06 (♂), 7.75–8.33 (♀) vs. 7.45–7.95 (♂), 7.52 (♀) times longer than board; movable chelal finger 1.79–1.83 (♂), 1.73–1.92 (♀) times vs. 1.61–1.68 (♂), 1.57–1.69 (♀) times longer than hand), the relative position of trichobothrium sb (sb 1.20–1.22 times vs. 1.67–1.70 times as far from st as from b) and the number of blades of coxal spines (12–13 vs. 8–9).

Tyrannochthonius umidus 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), the number of setae on sternites VI–Ⅹ (7–9 vs. 6) and a larger body size (body length min. 1.82 mm vs. max. 1.56 mm; chelal length min. 1.50 mm vs. max. 1.30 mm; palpal femur length min. 1.07 mm vs. max. 0.88 mm) ( Mahnert 2009; Gao et al. 2018, 2020).

Distribution. Known only from the type locality.

Figures

FIGURE 116. Da Cave, type locality of Tyrannochthonius umidus sp. nov., A–B. Inside the cave entrance; C–D. Areas where T. umidus sp. nov. specimens were collected; E. Live male of T. umidus sp. nov. in its natural environment.

FIGURE117.Tyrannochthoniusumidussp.nov.,A.Holotypemale,habitus(dorsalview);B.Paratypefemale,habitus(dorsalview).

FIGURE 118. Tyrannochthonius umidus sp. nov., holotype male (A–F), paratype female (G): A. Left chela (lateral view); B. Left chela (dorsal view); C. Carapace (dorsal view); D. Left chelicera (dorsal view); E. Left pedipalp (minus chela, dorsal view); F. Male genital area (ventral view); G. Female genital area (ventral view).

FIGURE 119. Tyrannochthonius umidus sp. nov., holotype male: A. Carapace (dorsal view); B. Left chelicera (dorsal view), with details of teeth; C. Coxal spines on coxae II (ventral view); D. Left pedipalp (minus chela, dorsal view); E. Rallum. Scale bars: 0.20 mm (A–B, D); 0.10 mm (C, E).

FIGURE 120. Tyrannochthonius umidus sp. nov., holotype male: A. Left chela (lateral view), with details of teeth and with trichobothrial pattern; B. Left chela (dorsal view); C. Leg I (lateral view); D. Leg IV (lateral view). Scale bars: 0.20 mm.