Tyrannochthonius pandus, Hou & Gao & Zhang, 2022

Hou, Yanmeng, Gao, Zhizhong & Zhang, Feng, 2022, Two new species of cave-adapted pseudoscorpions (Pseudoscorpiones, Chthoniidae) from Yunnan, China, ZooKeys 1097, pp. 65-83 : 65

Tyrannochthonius pandus sp. nov.

Chinese name. 弯指暴伪蝎 Figs 2 , 3 , 4 , 5

Type material.

(Figs 1A , 6 ) Holotype: China • ♂; Yunnan Province, Luxi County, Luyuandong Village, the Ancient Alu Cave National Park of China, Biyu Cave; 24°34.01'N, 103°45.16'E; 1722 m a.s.l.; 13 Oct. 2021; Zegang Feng, Yanmeng Hou, Lu Zhang and Liu Fu leg.; dark zone; Ps.- MHBU -HBUARA#2021-438-01. Paratype: • 1♀; the same data as the holotype; Ps.- MSWU -HBUARA#2021-438-02.

Diagnosis.

Moderately sized troglomorphic species with elongate appendages; carapace without eyes or eyespots; anterior margin of carapace gently serrate, epistome small, pointed, triangular, with 2 setae flanking base; posterior margin of carapace with 2 setae; tergites I-III with 2 setae; lacking chemosensory setae on dorsum of chelal hand; chelal fingers distinctly curved in dorsal view, with numerous large, gently curved, well-spaced teeth.

Etymology.

The specific name is derived from the Latin word " pandus ", meaning curved, refers to the curved chelal finger.

Description.

Adult male (Figs 2 , 3A , 4A-D , 5 ). Color: generally pale yellow, chelicerae, pedipalps and tergites slightly darker, soft parts pale (Figs 2 , 3A ). Cephalothorax (Figs 4B , 5A ): carapace 1.07 times longer than broad, gently narrowed posteriorly, surface smooth; anterior margin slightly serrate; without any traces of eyes; epistome very 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; without furrows but with 4 lyrifissures (Fig. 5A ). 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 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. 5C ); intercoxal tubercle absent; without sub-oral seta. Chelicera (Figs 4C , 5B ): large, about as long as carapace, 2.44 times longer than broad; 5 setae on hand, all setae acuminate, ventrobasal seta shorter than others; movable finger with one medial seta. Cheliceral palm with moderate hispid granulation dorsally. Both fingers well provided with teeth, fixed finger with 11 teeth, distal one largest; movable finger with 8 retrorse continuous small teeth; galea completely vestigial (Fig. 5B ). Rallum with 8 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. 5D ). Pedipalp (Figs 4A , 5E-H ): surface of palpal segments smooth; setae generally long and acuminate; femur 7.36, patella 2.55, chela 7.47, hand 2.80 times longer than deep; movable finger 1.71 times longer than hand and 0.64 times longer than chela, without large basal apodeme, only slightly sclerotized section present. Femur and dorsal hand without tactile setae but with 1 distal lyrifissure on patella (Fig. 5E ). 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 finger, very close to chelal teeth; dx situated distal to et; sb situated closer to st than to b; b and t situated subdistally, b situated at same level as est; t situated distal to est (Fig. 5F ). Microsetae (chemosensory setae) absent on hand and both chelal fingers. Sensilla absent. A tiny antiaxial lyrifissure present at base of fixed finger (slightly distal to ist). Both chelal fingers with a row of teeth, homodentate, spaced regularly along the margin, larger teeth present in the middle of the row, becoming smaller distally and proximally: fixed finger with 45 large, gently curved, well-spaced teeth, without intercalary teeth; movable finger with 44 small (slightly smaller than the teeth on fixed finger), retrorse, gently curved and well-spaced teeth (Fig. 5F ). Chelal fingers distinctly curved in dorsal view (Fig. 5H ). Opisthosoma: generally typical; pleural membrane finely granulate. Tergites and sternites undivided; setae uniseriate and acuminate. Tergal chaetotaxy I-XII: 2: 2: 2: 3: 4: 4: 4: 5: 5: 4: T2T: 0; tergites VIII and IX each with an unpaired median seta. Sternal chaetotaxy IV-XII: 10: 10: 9: 9: 9: 9: 8: 0: 2; sternites VI-IX with unpaired median seta. Anterior genital operculum with 10 setae, genital opening slit-like, with 15 marginal setae on each side (Fig. 4D ). Legs (Fig. 5I, J ): generally typical, long and slender. Femur of leg I 1.92 times longer than patella and with 1 lyrifissure at the base of femur; tarsus 2.50 times longer than tibia. Femoropatella of leg IV 3.67 times longer than deep; tibia 6.29 times longer than deep; with basal tactile setae on both tarsal segments: basitarsus 4.00 times longer than deep (TS = 0.35), telotarsus 14.50 times longer than deep and 2.90 times longer than basitarsus (TS = 0.33). Setae of leg I (trochanter to tibia) 3: 13: 12: 9, setae of leg IV (trochanter to basitarsus) 1: 3: 6: 9: 8. Arolium slightly shorter than the claws, not divided; claws simple. Dimensions of male holotype (length/width or, in the case of the legs, length/depth in mm; ratios in parentheses). Body length 1.41. Pedipalps: trochanter 0.18/0.13 (1.38), femur 0.81/0.11 (7.36), patella 0.28/0.11 (2.55), chela 1.12/0.15 (7.47), hand length 0.42/0.15 (2.80), movable finger length 0.72. Chelicera 0.44/0.18 (2.44), movable finger length 0.24. Carapace 0.45/0.42 (1.07). Leg I: trochanter 0.13/0.11 (1.18), femur 0.46/0.06 (7.67), patella 0.24/0.05 (4.80), tibia 0.20/0.04 (5.00), tarsus 0.50/0.04 (12.50). Leg IV: trochanter 0.20/0.11 (1.82), femoropatella 0.66/0.18 (3.67), tibia 0.44/0.07 (6.29), basitarsus 0.20/0.05 (4.00), telotarsus 0.58/0.04 (14.50).

Adult female (Figs 3B , 4E ). Mostly same as males. Anterior genital operculum with 10 setae plus 7 setae on posterior margin. Body length 1.67. Pedipalps: trochanter 0.24/0.13 (1.85), femur 0.88/0.13 (6.77), patella 0.28/0.11 (2.55), chela 1.20/0.17 (7.06), hand length 0.49/0.17 (2.88), movable finger length 0.76. Chelicera 0.45/0.21 (2.14), movable finger length 0.23. Carapace 0.46/0.46 (1.00). Leg I: trochanter 0.14/0.11 (1.27), femur 0.50/0.06 (8.33), patella 0.26/0.06 (4.33), tibia 0.21/0.05 (4.20), tarsus 0.53/0.04 (13.25). Leg IV: trochanter 0.21/0.12 (1.75), femoropatella 0.70/0.19 (3.68), tibia 0.46/0.07 (6.57), basitarsus 0.21/0.06 (3.50), telotarsus 0.62/0.04 (15.50).

Remarks.

Compared with the other six cave-dwelling species of the genus in China, Tyrannochthonius pandus sp. nov. is most similar to T. ganshuanensis in having only 2 setae on tergites I-III, the same chaetotaxy of carapace and triangular, a small epistome, but differs in the shape of teeth on chelal fingers (large, gently curved, well-spaced teeth, without intercalary teeth in T. pandus , but with pointed, well-spaced and intercalary teeth in T. ganshuanensis ), the relative position of the trichobothria on the movable chelal finger (sb situated closer to st than to b in T. pandus , but sb situated closer to b in T. ganshuanensis ). Tyrannochthonius pandus sp. nov. can be easily separated from T. akaleus by a smaller body size (1.67 vs. 2.10 mm in female), the teeth pattern on chelal fingers (intercalary teeth absent in T. pandus , but present in T. akaleus ); from T. harveyi by the different setae number on the anterior and posterior margins of the carapace ( T. pandus with 6 and 2 setae, respectively, but T. harveyi with 4 and 4 setae, respectively), the shape of the epistome (long and pointed in T. pandus , but rounded and inconspicuous in T. harveyi ), the number of rallar blades (8 in T. pandus , but 6 in T. harveyi ); and from T. zhai , T. chixingi and T. antridraconis by the number of setae on the anterior tergites (tergites I-III with 2 setae in T. pandus , but the other three with 4 setae). In addition, compared to the new species, T. zhai differs by the shorter body length (1.40 vs. 1.67 mm in female) and lacking an epistome; T. chixingi and T. antridraconis differs from the new species also by the presence of intercalary teeth on the fixed chelal finger ( Mahnert 2009; Gao et al. 2018; Gao et al. 2020).

Distribution.

This species is known only from the type locality, Biyu Cave (Figs 1A , 6 ). Biyu Cave is one of the tourist caves in the Ancient Alu Cave National Park of China, with the entrance located in the Jilong hillside. This beautiful cave is a valley type karst cave, with an internal height of 2 to 5 m and a width of 1 to 30 m. The cave has a latticed distribution. The stalactites in this cave are jasper colored, so it is called Biyu Cave (a quote from the cave’s interior slogan). The specimens of this new species were collected from under a stone and on a stone wall in an undeveloped area of the cave that is still in a natural condition. It is a small, dark, high humidity and low temperature space (temperature: 11 °C, humidity: 90%), which is suitable for the survival of the species.

Figures

Figure 1. Study area, general cave locations, and type locality for each species, Yunnan Province, China A Biyu Cave, Tyrannochthonius pandus sp. nov. B Laoxueyan Cave, Lagynochthonius laoxueyanensis sp. nov.

Figure 2. Tyrannochthonius pandus sp. nov., male habitus. Photographed when it crawled on stony natural habitat.

Figure 3. Tyrannochthonius pandus sp. nov. A holotype male, dorsal view B paratype female, dorsal view. Scale bars: 0.5 mm.

Figure 4. Tyrannochthonius pandus sp. nov., holotype male (A-D), paratype female (E) A chelal fingers (lateral view) B carapace (dorsal view) C left chelicera (dorsal view) D male genital area (ventral view) E female genital area (ventral view). Scale bars: 0.1 mm.

Figure 5. Tyrannochthonius pandus sp. nov., holotype male A carapace (dorsal view) with a detail of anterior margin 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 with trichobothrial pattern (abbreviations explained in Material and methods) G finger tips of chela (lateral view) H left chela (dorsal view) I leg I (lateral view) J leg IV (lateral view). Scale bars: 0.25 mm (A-B, E-F, H-J); 0.10 mm (C-D, G).

Figure 6. Biyu Cave, type locality of Tyrannochthonius pandus sp. nov. A entrance B access to an undeveloped area C area where T. pandus specimens were collected. D, E beautiful cave landscapes inside the cave F exit.