Gymnobisium megalodontum, Neethling & Neethling, 2023

Neethling, J. A. & Neethling, C., 2023, A systematic revision of the South African Gymnobisiidae (Pseudoscorpiones: Neobisioidea), Zootaxa 5256 (6), pp. 501-543 : 520-524

Gymnobisium megalodontum sp. nov.

Figs 14–17

Holotype: ♂, SOUTH AFRICA, Free State, Harrismith, Platberg Nature Reserve , 28°16′S, 29°11′E, 1967m a.s.l., Montane bushveld, Leaf litter sifting, leg. J.A. Neethling, 14.III.2012 ( NMBAP 00346 ).

Paratypes: 2♂, Same data as holotype ( NMBAP 00345 ) .

Etymology. The species name is a compound of the ancient Greek words megálo, meaning great, and dónti, meaning tooth. The name refers to the lightly sclerotized tooth at the posterior base of the venom tooth on the movable chelal finger, which is significantly enlarged in this species.

Diagnosis. Moderately sized species (chela length ♀ 1.22–1.27 mm, ♂ 1.12 –1.23 mm), with chelae more bulbous in females than in males (chela ratio ♀ 2.95–2.97 versus ♂ 3.32 –3.50 times longer than broad); fixed finger multi-toothed structure with five strongly sclerotized teeth; cheliceral hand with five setae; galea with six rami; rallum with eight blades. Differs from all congeners by having a distinctly enlarged tooth just preceding the venom tooth of the movable chelal finger.

Description

Carapace: Somewhat broader than long in females, somewhat longer than broad in males, subquadrate, overall smooth and without furrow. Brown in colouration in both sexes. Two pairs of eyes located dorso-laterally at the front ( Fig. 14A, C ). Small seta located on the dorso-anterior margin of each of the posterior eyes. Female carapace with 28, male carapace with 27 setae, arranged 4: 6: 2: 4: 4: 8(7).

Abdomen: Tergites and sternites smooth, undivided and uniseriate, brown in both sexes ( Fig. 14A, C ). In both sexes the lateral and posterior edges of tergites I–XI are distinctly lighter in colour, tergite XII uniform brown. The tergal setae are located on the posterior edge of each tergite, within the lighter coloured band. In both sexes sternites X–XI same colour as tergites; III–IX lighter brown; I & II tan ( Fig. 14B, D ). Sternites I and II are fused and hardly distinguishable. Female operculum with seven setae loosely grouped in the centre of the posterior margin of sternite II. Males with 20 setae at the operculum cluster on sternites II, seven situated centrally along the posterior margin of sternites II with another 13 clustered centrally just anteriorly. Male sternites III with 13 setae situated centrally along the anterior margin, at the genital opening. Pleural membrane cream to light yellow in colour, faintly papillate.

Tergal chaetotaxy: 7(7): 10(10): 11(11): 12(13): 12(12): 12(12): 12(13): 11(12): 11(11): 10(9): 11(10): 2(2). Sternal chaetotaxy: 7(20):?(?): 17(18): 18(17): 14(16): 14(16): 14(16): 13(13): 12(15): 11(11): 11(10): 2(2).

Pedipalp: All segments smooth and dark orange-brown in colour in both sexes. Trochanter cone-shaped and rounded anteriorly, curved slightly posteriorly. Base narrow, widening distally. Setae present on the anterior surface. Femur slender, 3.30–3.55 (♀) to 3.67–3.75 (♂) times longer than wide, somewhat constricted basally, widening just distal of base. Deep disto-prolateral excavation present. Setae absent from base, though distributed evenly over rest of surface. Patella constricted and slightly angled at base, widening markedly distal at around a third segment length, 2.32 (♀) to 2.48–2.66 (♂) times longer than wide. Several small lyriform fissures present on the dorsal surface, just distal of base. Two larger lyriform fissures present latero-dorsally from these, where the segment starts to widen. Very shallow disto-prolateral excavation present. Setae sparse at base, more numerous on wide part of patella ( Fig. 16B ).

Chela: In both sexes smooth and uniformly dark orange-brown. Female hand larger, prolateral surface more convex, than those of males. Male hand smaller, markedly less convex prolaterally ( Fig. 15B, D ). Viewed retrolaterally, female chelal hand presents a somewhat rectangular shape, less pronounced in males ( Fig. 15A, C ). Pedicel regular in both sexes, retrolateral condyle small but distinct and rounded. Fingers thicker, shorter than hand (without pedicel) in females, same length as hand (without pedicel) in males, and curved slightly prolaterally. Fixed and movable chelal fingers with eight and four trichobothria respectively ( Fig. 16A ).

Terminal multi-toothed structure extends slightly beyond venom tooth of movable finger in females, equidistant with venom tooth in males. In both sexes this structure is small, containing five strongly sclerotized teeth; front tooth significantly larger than the four teeth behind it ( Fig. 16C ). Both fingers with rounded, juxtadentate teeth situated on flexible lamellae. Lamellae originating roughly one third finger length from base on both female fingers. Lamella on male fixed finger originating just over one third finger length from base, on movable finger just distal of finger midpoint. Female fixed finger with 36–38 lightly sclerotized, juxtadentate teeth, eight to nine proximal to lamella base, together with five strongly sclerotized teeth on distal structure. Male fixed finger with 41–43 lightly sclerotized, juxtadentate teeth, 13–14 proximal to lamella base, together with five strongly sclerotized teeth on distal structure. Female movable finger with 35–36 lightly sclerotized, juxtadentate teeth, eight to nine proximal to lamella base. Male movable finger with 43–45 lightly sclerotized, juxtadentate teeth, 17–19 proximal to lamella base. Both sexes possess a distinctly enlarged, lightly sclerotized, tooth situated between the terminal lamellae teeth and the venom tooth ( Fig. 16C ). Two thickened, spine-like setae present on distal end of movable finger in both sexes.

Chelicera: Hand with five long and acuminate setae, es shorter ( Fig. 16D ). Female fixed finger with 12 teeth, male with 11. Female moveable finger with eight teeth, male with six. Galea of both sexes divided into six rami ( Fig. 16E ). Rallum of both sexes with eight long, acuminate blades ( Fig. 16F ). Lamina exterior absent in both sexes.

Coxae and legs: Pedipalpal coxae same colour, or slightly lighter, than rest of pedipalps. Coxae I–IV cream to tan. Legs I–IV light brown to tan in colour. All legs diplotarsate with subterminal tarsal setae dentate distally; claws simple; arolium shorter than claws.

Measurements (mm): Body length ♀ 1.86– 2.10 ♂ 1.75–1.80; Carapace ♀ 0.58–0.59 x 0.60–0.62 (0.95–0.97) ♂ 0.53 –0.58 x 0.52–0.56 (1.02–1.03); Chelicera ♀ 0.43–0.45 x 0.22–0.23 (1.95–1.96) ♂ 0.35 –0.38 x 0.19–0.20 (1.84–1.90), movable finger length ♀ 0.26– 0.28 ♂ 0.20–0.22; Pedipalps: femur ♀ 0.64–0.66 x 0.18–0.20 (3.30– 3.55) ♂ 0.60 –0.66 x 0.16–0.18 (3.67–3.75), patella ♀ 0.58 x 0.25 (2.32) ♂ 0.56 –0.57 x 0.21–0.23 (2.48–2.66), chela ♀ 1.22–1.27 x 0.41–0.43 (2.95–2.97) ♂ 1.12 –1.23 x 0.32–0.37 (3.32–3.50), hand ♀ 0.67–0.69 x 0.41–0.43 (1.60–1.63) ♂ 0.60 –0.67 x 0.32–0.37 (1.81–1.87), movable finger length ♀ 0.49– 0.51 ♂ 0.52–0.56; Leg I: femur ♀ 0.31–0.32 x 0.08–0.09 (3.55–3.87) ♂ 0.27 –0.30 x 0.08 (3.37–3.75), patella ♀ 0.22–0.24 x 0.08–0.09 (2.67– 2.75) ♂ 0.19 –0.22 x 0.08 (2.37–2.75), tibia ♀ 0.26–0.28 x 0.08 (3.25–3.50) ♂ 0.22 –0.26 x 0.06–0.07 (3.14–3.71), metatarsus ♀ 0.15–0.16 x 0.06 (2.50–2.67) ♂ 0.13 –0.15 x 0.06 (2.17–2.50), tarsus ♀ 0.17–0.19 x 0.05 (3.40–3.80) ♂ 0.18 –0.20 x 0.06 (3.00–3.33); Leg IV femoropatella ♀ 0.56–0.58 x 0.12–0.14 (4.14–4.67) ♂ 0.52 –0.57 x 0.12– 0.14 (4.07–4.33), tibia ♀ 0.47–0.49 x 0.08–0.09 (5.44–5.87) ♂ 0.45 –0.50 x 0.07–0.08 (6.25–6.42), metatarsus ♀ 0.18–0.19 x 0.07 (2.57–2.71) ♂ 0.15 –0.20 x 0.07 (2.14–2.86), tarsus ♀ 0.26–0.28 x 0.06 (4.33–4.67) ♂ 0.22 –0.26 x 0.06 (3.67–4.33).

Remarks. Although Gymnobisium megalodontum sp. nov., G. inukshuk , G. octoflagellatum and G. prionotogladiatum sp. nov. all have an isolated, lightly sclerotized tooth at the posterior base of the venom tooth, those found in G. megalodontum sp. nov. are significantly larger ( Fig. 17A, B ).

Additional material examined. SOUTH AFRICA: Free State: 1♂, Fouriesburg, Meiringskloof , 28°36′S, 28°13′E, 1799m a.s.l., Montane bush, Leaf litter sifting, leg. J.A. Neethling, 20.III.2017 ( NMBAP 00334 ); 1♀ , 6♂, 3 Tritonymphs, Harrismith, Platberg Nature Reserve , 28°16′S, 29°11′E, 1967m a.s.l., Montane bushveld, Leaf litter sifting, leg. J.A. Neethling, 14.III.2012 ( NMBAP 00335 ) .

Figures

FIGURE 14. Digital microscope photographs of Gymnobisium megalodontum sp. nov., Female (A, B) and Male (C, D). A, C. Dorsal view; B, D. Ventral view. Scale bar: 1.00 mm.

FIGURE 15. Digital microscope photographs of Gymnobisium megalodontum sp. nov. right chela: Female (A, B) and Male (C, D). A, C. Retrolateral view; B, D. Dorsal view. Scale bar: 1.00 mm.

FIGURE 16. Gymnobisium megalodontum sp. nov. A. Female right chela, retrolateral view; B. Female right pedipalp, dorsal view; C. Female chelal fingers, anterior retrolateral view; D. Female left chelicera, dorsal view; E. Galea; F. Rallum. Scale bars: A, B: 0.50 mm; C, D: 0.20 mm; E, F: 0.10 mm.

FIGURE 17. Anterior retrolateral views of movable chelal fingers showing differences in isolated teeth at base of venom tooth. A. Gymnobisium octoflagellatum Beier, 1947, with small tooth; B. G. megalodontum sp. nov. with enlarged tooth.