Tyrannochthonius iuiu, Guimarães & Prado & Ferreira, 2025

Guimarães, Lucas, Prado, Guilherme C. & Ferreira, Rodrigo L., 2025, Two new species of Tyrannochthonius Chamberlin, 1929 (Pseudoscorpiones: Chthoniidae) from caves in Brazilian semiarid region., Zootaxa 5706 (3), pp. 367-382 : 369-373

Tyrannochthonius iuiu sp. nov.

Material Examined. Holotype female (ISLA 126406), preserved in ethanol: Brazil, Iuiú, Bahia, Olho D’água do Coitezeiro ( 14°27'58.76"S 43°39'26.24"W), October 26, 2021, collected by R. L. Ferreira . Paratype male ( ISLA 126407) , Paratype female ( ISLA 126409) same data as the holotype .

Etymology. The specific epithet iuiu is a noun in apposition and refers to Serra de Iuiú (Iuiú Hill), southwestern Bahia State, Brazil, where the species was discovered.

Diagnosis. Tyrannochthonius iuiu sp. nov. most closely resembles T.migrans based on the following combination of characters: presence of two pairs of eyes, carapace chaetotaxy 4+2: 4: 4: 2: 2, chelicerae with five setae on the hand, number of teeth on the movable cheliceral finger ( 10–12 in T. iuiu sp. nov. and 10–15 in T. migrans ), and coxal chaetotaxy 3: 4: 5: 5 (including coxal spines). It differs from T. migrans in number of chelal teeth: fixed finger with 23 teeth and 11 intercalary microdenticles (in T. migrans 16–19 teeth and 7–9 microdenticles), movable finger with 20 teeth (in T. migrans 10–12), movable chelal finger 1.6–1.7 times longer than hand (in T. migrans 2.1–2.2); presence of two lyrifissures on sternite II, one on each side of genital opening; leg I tarsus 10.3 longer than wide (in T. migrans 7.0–7.9); leg IV tarsus 11.0 longer than wide (in T. migrans 7.3–8.7).

Description. Body beige, slightly translucent, with darker chelicerae and carapace ( Figs 1A, C ), vestitural setae simple, thin and sharp, anteriorly projected on the prosoma and posteriorly projected on the opisthosoma.

Carapace. Slightly constricted posteriorly, with a small difference between ocular width and posterior width of 0.09 mm. Surface smooth, without any furrows. Presence of two pairs of eyes, the anterodorsal ones without defined lens ( Fig. 2C ). Anterior margin smooth, epistome bifid and small, with 2 setae flanking the base ( Fig. 2A ). Carapace chaetotaxy: 4+2: 4: 4: 2: 2 (18), simple setae, median lateral ones shorter.

Tergites. Undivided, smooth surface. Chaetotaxy uniseriate: I–XI 4: 4: 4 (6): 6: 6 (5): 6 (5): 6: 6: 6: 6: 4.

Coxae. Palpal: Manducatory process with two acuminate distal setae, and 3 coxal setae arranged in a triangle. Pedal: Apex anterior of coxae I with an acute projection ( Fig. 3D ), coxae II with six coxal spines with branched apex (4–6 branches each, Fig. 2D ), arranged in an oblique row ( Figs 3B, D ). Intercoxal tubercle absent. Chaetotaxy of pedal coxae: 3: 4: 5: 5. ( Fig. 3D ).

Male genital operculum. Genital opening slit-like; sternite II with 6–7 setae; sternite III with 8–7 marginal setae on each side; one pair of lyrifissures on each side of sternite III ( Fig. 3C ).

Female genital operculum. Sternite II with 5–6 setae on posterior margin, sternite III with 9 setae scattered on median area. ( Fig. 2E ).

Sternites. Male chaetotaxy III‒XI: 8: 10: 10: 8: 8: 8: 8: 4, anal operculum with 2 ventral setae. Female chaetotaxy IV–XI: 8: 9: 7: 6: 7: 7: 7: 2 + 2 anal setae.

Chelicerae. 0.21 times longer than wide. Hand with 5 setae ( Fig. 2B ), 3 lyrifissures at the base of the fixed finger (dorsally visible) and small spines projecting anteriorly ( Figs 4C, D ). Movable cheliceral finger with 1 medial seta ( Fig. 4D ), and 12 acute teeth (4 proximal ones shorter), galea absent; fixed cheliceral finger with 6 teeth (including a large distal one). External and internal serrulae with 17 and 13 blades, respectively. Rallum with 7 unilaterally pinnate blades ( Figs 4C, D ).

Pedipalp. Trochanter 1.74, femur 4.67, patella 2.39, chela 4.75, hand 1.93 times as long as wide; femur 2 times as long as patella; movable chelal finger 1.57 times as long as hand and 0.41 times as long as chela. Movable chelal finger with apodeme slightly sclerotized, with 24(23) well-spaced acute teeth (except the six most basal ones, which are vestigial and rounded), and 5(6) intercalary microdenticles in the distal portion ( Figs 4A, B ). Fixed chelal finger with 23 acute teeth, 11 intercalary microdenticles along almost entire length, and 6 vestigial teeth in the basal region ( Figs 4A, B ). Trichobothria: ib and isb adjacent, located submedially on the dorsum of the hand. In the fixed finger, esb is slightly distal to eb and slightly more distal to ist. In the posteromedial portion, it is slightly distal to est. In the distal portion, et is proximal to dx. In the movable finger, sb is halfway between b and st; t is distal to b ( Fig. 4A ), b much closer to t than sb (ratio distance sb–b / b–t = 4.2).

Leg I. Femur 2.00 times as long as patella, tarsus 2.06 times as long as tibia. Arolium undivided, slightly shorter than simple claws. One lyrifissure at the apex of the femur ( Fig. 5C ).

Leg IV. Femur and patella 2.86 times as long as wide, tibia 4.85 times as long as wide, basitarsus 3.00 times as long as wide, telotarsus 11.0 times as long as wide and 2.20 times as long as basitarsus. Arolium undivided, slightly shorter than simple claws. One lyrifissure at the anterior face of the femur ( Fig. 5A ).

Measurements (mm): (length/width or depth in mm and ratios in parentheses calculated with three significant digits). Female holotype: Body length 1.39 (male paratype 1.00 mm [measured during SEM analysis]). Carapace 0.41/0.44 (0.93). Palps: trochanter 0.19/0.11 (1.72), femur 0.48/0.10 (4.8), patella 0.24/0.10 (2.4), chela 0.72/0.15 (4.8), movable finger length 0.46. Leg I: trochanter 0.12/0.09 (1.33), femur 0.28/0.06 (4.66), patella 0.14/0.05 (2.8), tibia 0.15/0.04 (3.75), tarsus 0.31/0.03 (10.3). Leg IV: trochanter 0.12/0.10 (1.2), femoropatella 0.49/0.19 (2.57), tibia 0.34/0.06 (5.66), basitarsus 0.15/0.05 (3.0), telotarsus 0.33/0.03 (11.0).

Ecological Remarks. Specimens of Tyrannochthonius iuiu sp. nov. are exclusively recorded in Olho D’Água do Coitezeiro Cave, located in the municipality of Malhada, Bahia State, Brazil. This cave features a single entrance ( Fig. 6B ), formed by the resurgence of a subterranean drainage system that remains active throughout the year ( Fig. 6D ), although discharge volume varies considerably between the dry and rainy seasons. The main conduit, shaped by the drainage flow, is relatively narrow but connects to upper-level passages and galleries ( Fig. 6C ). These elevated areas remain humid but are not directly influenced by flowing water. Tyrannochthonius iuiu sp. nov. was observed within one of these upper galleries, sheltered beneath rocks on the cave floor. Potential prey, such as springtails (Collembola) and mites, were also present in the same microhabitats. Olho D’Água do Coitezeiro Cave is situated atop the Serra do Iuiú, where the surrounding vegetation remains relatively well preserved ( Fig. 6A ). The rugged terrain created by limestone outcrops limits access and has restricted agricultural and livestock activities in the area. Furthermore, the cave interior shows minimal signs of human disturbance, indicating a high level of habitat integrity.

Figures

FIGURE 1. Habitus. A) Tyrannochthonius iuiu sp. nov., dorsal view; B) Tyrannochthonius aratu sp. nov., dorsal view; C) T. iuiu sp. nov., ventral view; D) T. aratu sp. nov., ventral view. Scale bars: 1.0 mm.

FIGURE 2. Tyrannochthonius iuiu sp. nov. Female holotype. A) Detail of epistome in the posterior margin of carapace; B) Left chelicera, antiaxial view, showing setae; C) Carapace, dorsal view; D) Detail of coxae II, showing arrangement of coxal spines; E) Genitalia, ventral view. Scale bars: (A–E) 0.1mm.

FIGURE 3. Tyrannochthonius iuiu sp. nov. Male paratype. A) Manducatory process, ventral view; B) Coxal spines; C) Genitalia, showing lyrifissures (red circles); D) Body, ventral view. Scale bars: (A–C) 0.1 mm; (D) 0.25 mm.

FIGURE 4. Tyrannochthonius iuiu sp. nov. Male paratype. A) Left chela, showing trichobothrial patter, antiaxial view; B) Detail of left chela, showing the fingers and a lyrifissure on the fixed finger; C) Left chelicera, ventral view; E) Detail of the left chelicerae, showing small spines on the back of the hand (red circle) and lyrifissures (white circles). Scale bars: (A–D) 0.1 mm.

FIGURE 5. Tyrannochthonius iuiu sp. nov. Male paratype. A) Right leg I, showing claws and arolium; B) Right pedipalp, dorsal view; C) Right leg IV of female paratype, showing claws and arolium. Scale bars: (A–B) 0.3 mm; (C) 0.4 mm.

FIGURE 6. Habitat of Tyrannochthonius iuiu sp. nov. A) Landscape surrounding Olho D’Água do Coitezeiro Cave; B) Cave entrance; C) Upper galery inside the cave; D) Stream emerging from the cave.