Nepalmatoiulus angustus, Mikhaljova, 2023

Mikhaljova, Elena V., 2023, A contribution to the millipede fauna of China: descriptions of four new species of the genus Nepalmatoiulus Mauriès, 1983 from high-altitude areas of Yunnan Province (Diplopoda, Julida, Julidae), Zootaxa 5357 (2), pp. 285-300 : 286-288

Nepalmatoiulus angustus sp. nov.

Figs 1–12

Material examined. Holotype: male (dissected) ( ZMUM), China, Yunnan Province, SSW Lanping , left bank Qijing R., 2.8 km SSE Dacuntuocun, 26°14´03´´ N, 99°17´03´´ E, H = 2650 m, 27.05. 2018, leg. I. Belousov, I. Kabak. Paratypes: 1 female (dissected) ( ZMUM), same data as for holotype ; 1 male (dissected) ( ZMUM), China, Yunnan Province, WSW Lanping Qing & Qijing div., 4.5 km SE Yulongchang , 26°24´25´´ N, 99°16´59´´ E, H = 3355 m, 22.05. 2018, leg. I. Belousov, I. Kabak.

Diagnosis. Differs from congeners mainly by the mesomeral process with relatively short and thick apex (a in Fig. 8 ), by the very narrow velum, by the promere distally slightly expanded and apically very slightly obliquely rounded, by the male coxa 2 with two mesapical oral setae. To a certain degree similar to Nepalmatoiulus muli Mikhaljova, 2020a but differs from the latter by specific characters (see Remarks below).

Description. Male. Length in alcohol 32.0–34.0 mm, midbody vertical diameter about 2.5 mm, vertical diameter of anterior body part about 2.0 mm with 55(–2) (in holotype) and 53(– 1) (in paratype) rings, excluding telson. Coloration in alcohol: from dark gray with a pale swoop (in paratype) to gray-dark brown (in holotype) with light brown longitudinal broad stripe and with dark brown narrow middorsal longitudinal line. Legs light brown with dark brown distal parts. Antennae dark brown. Eye patches black. Head dark brown with yellow anterior part. Gnathochilarium yellow. Apical portion of the marbled brown mandible stipital lobe with yellow border.

Head smooth, 1+1 epicranial setae, 4 supralabral setae, not less than 32 labral setae. Eye patches almost oval, composed of not less than 46 ommatidia. Antennae medium-sized, rather slender and clavate. Antennomeres 5 and 6 with incomplete distodorsal corolla of sensilla basiconica. Mandibular stipites with oval, lenticular smooth lobes. Gnathochilarium with not less than 12 nonapical stipital setae; lamellae linguales each with 4 or 5 setae arranged longitudinally.

Collum laterally with distinct striae of different length at posterior margin not reaching to anterior margin, dorsally with distinct short striae at posterior margin. A transverse row of very sparse thin setae at hind edge of collum.

Body rings circular. Prozona smooth. Metazona with dense, regular, longitudinal striae reaching hind margin (20 or 21 striae in an approximate square with sides equal to metazonital length of a dorsal side of a midbody ring). Limbus straight, smooth (of Type 1 in Enghoff 1987). A transverse row of sparse, thin setae at hind edge of metazonites, setae gradually growing denser toward telson. Ozopores small, lying behind suture between pro- and metazona without touching it. Caudal dorsal projection of telson straight and long, densely covered with setae and carrying at tip a claw-shaped process curved dorsally. Preanal ring and anal valves densely setose; subanal scale densely setose along caudal edge.

Legs relatively short and slender. Very delicately serrate ventral pads present on postfemur and tibia, starting from legs 2 ( Fig. 2 ); pads decreasing in size towards telson, totally disappearing on postfemur and remaining only on the most extreme tibial apex of hind legs. Claw of all legs at base with a setiform accessory claw ventrally, accessory claw relatively short (equal to claw length) in the anterior body part ( Fig. 4 ) and long (longer than claw) in the posterior body part. Leg pair 1 forming hook, the distal segment not in close contact with the basal segments (“Open hook” type in Enghoff 1987): coxa with one seta; postfemur with scaly-rugose ventral surface; distal segment without tarsal remnant and setae ( Fig. 1 ). Coxa 2 with two mesapical oral setae (o), a gland opening positioned in central and apical position ( Fig. 5 ) according to Enghoff (1987). Penis with an expanded basal part (a bit like a pear), about 1.5 × longer than wide ( Fig. 3 ).

Gonopods slightly protruding. Anterior gonopod distally slightly expanded, apically very slightly obliquely rounded, distal margins of the apical excavation papillate (especially mesal margin), rudimentary telopodite as elongated oval, with seta ( Figs 6, 7 ). Flagellum slender, of medium length, caudally covered with cuticular conical spikes in the distal part, excluding glabrous apical portion ( Fig. 10 ) (failed to see the basal part of the flagellum). Posterior gonopods very slender ( Figs 8 , 11 ). Mesomeral process with relatively short and thick, slightly arched forward papillate apex (a). Anterior surface of the mesomeral process with longitudinal subbasal deepening (n) ( Fig. 8 ). Velum (v) very narrow, very steeply sloping, its margin smooth, without a notch near mesomeral process. Additional membrane (m) with a serrate edge. Acicular process (ap) of a flagellum-guiding flap arising from posterior margin of solenomeral furrow long. Solenomere (sl) spinose, basally with blade (bb), covered with spikes throughout ( Figs 8, 9 ).

Female. Length in alcohol about 33.0 mm, midbody vertical diameter about 2.5 mm, vertical diameter of anterior body part about 2.0 mm with 53(–2) rings, excluding telson. Coloration of the ring lateral surfaces darker than one in male. Vulva as in Fig. 12 .

Etymology. The specific epithet refers to the narrow velum of the posterior gonopods. Adjective.

Remarks. Nepalmatoiulus angustus sp. nov. differs from N. muli mainly by the larger body length (about 33.0 mm) and smaller midbody vertical diameter (about 2.5 mm) (vs. length—about 25.0 mm, midbody vertical diameter—about 3.0 mm in N. muli ), by the slenderer posterior gonopods, by the shorter and thicker apex (a in Figs 8 , 11 ) of the mesomeral process, by the narrower velum, by the shorter solenomere, by the promere distally slightly expanded, apically very slightly obliquely rounded (vs. promere distally not expanded, apically very obliquely rounded in N. muli ), by the male coxa 2 with two mesapical oral setae and a gland opening positioned in central and apical position (vs. male coxa 2 with one mesapical oral seta and a gland opening positioned in central and axial position in N. muli ), by the ovale, lenticular smooth lobes of gnathochilarium mandibular stipites (vs. subrectangular lobes in N. muli ).

Figures

FIGURES 1–5. Nepalmatoiulus angustus sp. nov., male holotype (ZMUM). 1. Leg 1, anterior view. 2. Leg 5. 3. Penis, caudal view. 4. Claw 5. 5. Coxa 2, anterior view. Abbreviation: o, mesapical oral seta. Scales: 10 μm (Fig. 4), 20 μm (Figs 1, 3), 100 μm (Figs 2, 5).

FIGURES 6–9. Nepalmatoiulus angustus sp. nov., male holotype (ZMUM). 6. Right promere, posterior view. 7. Distal part of right promere, posterior view. 8. Opisthomere, mesal view. 9. Solenomere, mesal view. Abbreviations: a, apex; ap, acicular process; bb, basal blade; m, accessory membrane; n, deepening; sl, solenomere; v, velum. Scales: 20 μm (Figs 7, 9), 100 μm (Figs 6, 8).

FIGURES 10–12. Nepalmatoiulus angustus sp. nov., male holotype (Figs 10, 11) and female paratype (Fig. 12) (ZMUM). 10. Flagellum apex, mesal view. 11. Distal part of mesomeral process, mesal view. 12. Vulva, posterior view. Scales: 10 μm (Figs 10, 11), 100 μm (Fig. 12).