Typhloiulus clavatus Antić, new species

Figs 9, 10, 15A

Material examined: Type specimens. Holotype male, CROATIA, Dalmatia, Otok, Stražbenica, Klenovac Pit (43.708100°N, 16.776683°E), 30 April 2016, T. Rađa leg. (NHMSC) . Paratype female, same data as for holotype .

Diagnosis. Typhloiulus clavatus is most similar to members of the subgenus Inversotyphlus, viz. T. lobifer, T. gellianae, and herein described T. gracilis and T. opisthonodus . These species are characterized by the presence of a very long opisthomere with a similarly shaped velum; the presence of a poorly developed, but visible opisthomeral lamella; and similar male sexual and habitus structures (see Discussion). The new species differs clearly in gonopod details, such as the presence of a robust promere with the apical half slightly curved anteriad and the presence of a very prominent and clavate mesomere.

Description. Based on holotype (male) 20 mm long, vertical diameter of the largest body ring 1.35 mm, body with 41 podous rings + 3 apodous rings + telson. Colouration: (Fig. 9A). Brownish. Head: (Fig. 9B). Labrum with three labral teeth, with 4 supralabral and 7+7 labral setae. Gnathochilarium with promentum kite-shaped, elongated; lamellae linguales with 4+3 setae in one row, stipites each with 3 setae. Antennae 2 mm long, length 148% of vertical diameter of the largest body ring. Length of antennomeres I–VIII (in mm): 0.12 (I), 0.42 (II), 0.36 (III), 0.31 (IV), 0.36 (V), 0.26 (VI), 0.12 (VII), and 0.05 (VIII). Length/width ratio of antennomeres I–VII: 0.75 (I), 2.8 (II), 2.4 (III), 2 (IV), 2 (V), 1.6 (VI), and 1 (VII). Antennomeres V and VI each with a terminal corolla of large bacilliform sensilla; antennomere VII with a terminal corolla of microsetae. Body rings: (Fig. 9D). The whole metazonal area with longitudinal striations. Metazonal setae fallen off. Telson: (Fig. 9C). Epiproct with a long preanal process, strongly curved downwards and covered by long dorsal and lateral setae. Paraprocts rounded, with numerous long setae. Hypoproct lenticular, with five long setae. Legs: First pair of legs modified, hook-shaped (Fig. 10A); coxa, postfemur, and tibiotarsus each with one seta, prefemur with four or five setae, femur with two or three setae. Tibiotarsus with a small tarsal remnant in the form of a prominent dorsal lobe. The tip of the first pair of legs tuberculate. Second pair of legs with poorly developed ventral pads on the tibia. Penis: (Fig. 10B). Bilobed. Lobes prominent, elongated. Ventral margin of body ring 7: (Fig. 9E). Well-developed, tapering distad, with rounded tip. Posterior margin right-angled to metazona. Gonopods: (Figs 10C–F, 15A). Promere (p) and mesomere (m) robust, both shorter than opisthomere (o). Promere (p) shorter than m; apical half slightly curved anteriad; laterally in the form of a shield; mesal lobe (ml) wide, subquadrangular, with three apical setae; telopodite (t) subcylindrical, tapering distad, over high ml. Mesomere (m) clavate in lateral/mesal view, subapically with anterior tuberculation. Opisthomere (o) slender, straight, and elongated; antero-mesally with poorly developed lamella (l); mesally with one spine; velum (v) unipartite, well-developed, tapering anteriad, with fimbriated tip. Solenomere (s) narrow, distally with several short spines.

Paratype (female) 25 mm long, vertical diameter of the largest body ring 1.5 mm, body with 47 podous rings + 2 apodous rings + telson.

Distribution. This species is known only from its type locality, Klenovac Pit in Dalmatia (Fig. 20, red circle).

Notes. Klenovac Pit is some 45 m deep and also inhabited by a stygobiotic Niphargus sp. ( Amphipoda).

Etymology. To denote the presence of a club-shaped mesomere. Adjective.