Sibiriulus rectangulus Mikhaljova, 2009, sp.n.

Sibiriulus rectangulus sp.n.

Figs. 24-29.

Material examined: Holotype: 1 male (IBSS), Russia, Republic of Altai, Gorno-Altaisk, stream, pitfall traps, collected 26 August 2001 by N.V. Levina. Paratypes: 4 females, 1 fragment (PSU), same locality as for holotype, collected 26 August 2001 by N.V. Levina; 1 male, 1 female (IBSS), Russia, Republic of Altai, Gorno-Altaisk, Betula forest, collected 28 August 2001 by N.V. Levina.

Diagnosis: This species differs from congeners mainly by the structure of the gonopod opisthomere, with the distal part bent at a near right angle anteriad, and with a strong inner process near the middle of the opisthomere length.

Description: Male. Body about 13 mm long; 0.5 – 0.6 mm in diameter, with 41(-2), 43(-2) segments, excluding telson. Coloration brown, with dark brown round spots at level of ozopores and closer to venter. Metazonites with a marbled dark brown transverse band. Thin axial line weakly discernible on dorsum. Anterior portion of head brown, with pattern of light spots of different size and configuration, vertex dark brown, occipital part light brown. Collum with frontal transverse dark brown band. Legs brown. Eyes black. Antennae dark brown.

Eye patches rounded subquadrate, each composed of 25 – 28 ocelli. Epicranial setae 1+1, supralabral setae 2+2, labral ones 8+8. Genae unmodified. Antennae medium-sized, rather slender and clavate, in situ reaching to somite 4. Length ratios of antennomeres 2–7 as 3.3:2.3:2.0:2.4:1.4:1, width ratios as 1.4:1.6:1.6:2.0:1.8:1, respectively. Antennomeres 5 and 6 with an incomplete distodorsal corolla of 4 – 5 sensory bacilli.

Gnathochilarium normal; stipe distally with two setae on outer side and with one seta closer to its medial portion as well as medially with group of short setae on low knob. Each lamella lingualis with two long distal setae and two short proximal setae, arranged longitudinally.

Body cylindrical, slender. Suture dividing pro- and metazona distinctly constricting both zonites. Ozopores small, lying behind suture without touching it. Metazona with striae failing to reach hind margin; 6 – 7 striae per approximately quarter of metazonital surface, i.e. between the dorsal midline and ozopore. Transverse row of sparse, thin, relatively short setae at hind edge of metazonites, setae gradually growing denser toward telson. Telson with densest longest setae and a short, dorsal subcylindrical projection (so-called tail) carrying tiny claw-shaped process directed caudad and somewhat ventrad. Anal valves relatively strongly bulging, densely setose. Anal scale subtriangular, setose only along caudal edge.

Legs thin, short; claws with thin, long, setiform, ventral outgrowth at base. Leg pair 1 (Fig. 24) unciform, with papillae apically, strong setae ventrally, and rounded, low, knob-shaped outgrowth of telopoditomere 2. Leg pair 2 unmodified, penes with subdiamond-shaped notch at tip (Fig. 25).

Gonopods as in Fig. 26. Pro- and mesomere closely attached to each other. Gonopod meso- and opisthomere subequal in height. Promere (Fig. 27) flattened, caudally papillate, with small knob at base. Flagellum long, filiform distally. Mesomere (Figs 28 – 29) front surface as plate, densely papillate, with longitudinal lowering along middle. Apex of mesomere with an apical fovea. Distal part of opisthomere bent at near right angle anteriad; inner strong process placed nearly at middle of opisthomere length; solenomere broad; mesal, spiniform distal process on inner side of opisthomere, somewhat curved caudad.

Female. Body about 16 mm long; near 1.0 – 1.1 mm in diameter, with 43(-2), 44(-2) segments,

excluding telson. Coloration lighter than in male. Ocelli 33 – 34. Walking legs as in male. Coxae of leg pair 2 without processes.

Etymology: The specific epithet refers to the distal part of gonopod opisthomere bent at a near right angle anteriad.