Neobisium radjai Dimitrijević, n. sp.

(Figs. 1–9; Table 1)

Derivatio nominis. The erected pseudoscorpion species is named after Tonći Rađa, a distinguished Croatian biospeleologist and the president of the Špiljar Speleological Society (Split, Croatia), who collected the type specimen of the new species. Over the last 25 years, Mr. Rađa significantly contributed to the better knowledge of biospeleology in the Balkan Peninsula.

Material examined. Holotype female labeled as follows: „ Bosnia and Herzegovina, Livno, village of Srđevići, Golubanjka Cave, 10.IX.2016, leg. T. Radja “ (white lebel, printed) / Holotypus Neobisium radjai n. sp. Dimitrijević det. 2017” (red label, printed).

Description. Carapace slightly longer than broad (Table 1; Figs. 1 and 9). Epistome in form of a low hyaline convexity (Fig. 4). No eyes or eye-spots developed. Nineteen setae distributed in four rows on carapax. Carapacal setal formula: 4 + 6 + 5 + 4 = 19. Carapace reticulate.

Chelicera 1.88 times as long as broad (Table 1; Fig. 3). Six setae situated on cheliceral palm, whilst one seta borne on movable cheliceral finger. Tubercle of movable cheliceral finger is a low hyaline convexity. Eleven and seven teeth of uneven size and shape present on fixed and movable cheliceral fingers, respectively. Flagellum of 13 blades. Only the two distal most blades pinnated anteriorly. All other blades smooth, acuminate and decrease in size proximally (Fig. 8).

Tergites I-X smooth, entire and uniseriate. The number of setae on tergites I-X is variable. Tergal setal formula: 3-4-4-5-6-6-7-8-9-8.

Female genital area: sternite II bears a cluster of 17 median setae, sternite III with 33 setae on posterior margin, whilst sternite IV carries 13 setae (Fig. 2). Along each stigma, on sternites III and IV, 3-4 supra-stigmatic setae present. Setal formula of sternites V-X as follows: 15-13-14-17-19-14. Pleural membrane granulostriate.

Male genital area: unknown.

Manducatory process of pedipalpal coxa bears four setae. All pedipalpal articles smooth and elongate (Figs. 5 and 9). Fixed and movable pedipalpal chelal fingers carry 178 and 145 teeth, respectively. Teeth on movable chelal finger square-topped and close-set in proximal part of the finger, similar in shape and size to teeth on the fixed chelal finger (Fig. 6). Four trichobothria on movable chelal finger and eight trichobothria on fixed the chelal finger. Pedipalpal femur 8.92 times as long as broad (Table 1), considerably longer than carapace. Pedipalpal patella (tibia) 4.79 times as long as broad (Table 1).

Leg IV: tibia, basitarsus and telotarsus each carry a single tactile seta (Fig. 7). Sub-terminal tarsal setae furcate; each branch has a few tiny spinules.

The linear measurements of different body structures and morphometric ratios are presented in Table 1.

Differential diagnosis. The new species is compared here with the morphologically closest species, Neobisium davidbengurioni Ćurčić & Dimitrijević, 2002 (from two caves on Mt. Durmitor, Montenegro) and N. marcchagalli B. Ćurčić & S. Ćurčić, 2002 (from the Velja Peć Cave, near Nikšić, Montenegro).

N. radjai n. sp. can be easily distinguished from N. davidbengurioni in several important aspects: the pedipalpal femur length/breadth ratio (8.92 vs. 7.75), pedipalpal femur length (3.48 mm vs. 2.17 mm), pedipalpal tibia length (2.06 mm vs. 1.81 mm), pedipalpal tibia length/breadth ratio (4.79 vs. 5.32), pedipalpal chela length (5.06 mm vs. 3.535 mm), pedipalpal chelal finger/pedipalpal chelal palm length ratio (2.07 vs. 1.41), number of carapacal setae (19 vs. 22), setal formula of tergites I-X (3-4-4-5-6-6-7-8-9-8 vs. 7-6-6-6-7-7-7-7-7-7), numbers of teeth on fixed and movable pedipalpal chelal fingers (178 and 145, respectively vs. 123 and 117, respectively) and setal formula of sternites II-IV (17-33-13 vs. 13-23-9) (Ćurčić et al. 2002).

From N. marcchagalli the newly erected species N. radjai differs also in several respects that enchance the distinction between these two cave-dwelling species: in the form of epistome (wide vs. triangular), number of carapacal setae (19 vs. 21), setal formula of tergites I-X (3-4-4-5-6-6-7-8-9-8 vs. 4-6- 6-6-8-8-8-9-9-9), number of setae on sternites II (17 vs. 14) and III (33 vs. 30), setal formula of sternites V-X (15-13-14-17-19-14 vs. 11-11-11-8-8-10) and number of teeth on both fixed and movable pedipalpal chelal fingers (178 and 145, respectively vs. 107 and 103, respectively) (Ćurčić et al. 2002).