Nepalmatoiulus arcuatus, 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 : 289-292

Nepalmatoiulus arcuatus sp. nov.

Figs 13–24

Material examined. Holotype: male (dissected) ( ZMUM), China, Yunnan Province, 11.5 km W Lanping SE Lajing, 3 km SE Jiaolieshan, 26°27´16´´ N, 99°18´42´´ E, H = 3050 m, 19.05. 2018, leg. I. Belousov, I. Kabak. Paratype: 1 female (dissected) ( ZMUM), same data as for holotype .

Diagnosis. Differs from congeners mainly by the perfectly arcuate margin of the velum, by the slender mesomeral process devoid of outgrowth, by the strongly obliquely rounded promere apex, by the absence of a notch of velum margin near the mesomeral process, by the male coxa 2 with two mesapical oral setae, one of which is very short/thin and practically not visible in anterior view. To a certain degree similar to Nepalmatoiulus pallidus Mikhaljova, 2020a but differs from it by specific characters (see Remarks below).

Description. Male. Length in alcohol about 29.0 mm, midbody vertical diameter about 1.5 mm, with 53(–1) rings, excluding telson. Coloration in alcohol marbled dark grey with brown narrow transverse line on caudal margin of each metazonite. Antennae and distal parts of legs dark brown; basal parts of legs light brown. Head dark brown with light brown anterior part. Eye patches black. Gnathochilarium marbled brown with yellow distal part. Apical portion of the dark brown mandibular stipital lobe with yellow border.

Head smooth, 1+1 epicranial setae, 4 supralabral setae, not less than 28 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 subtrapezoidal smooth lobes. Gnathochilarium with not less than 17 nonapical stipital setae on left side and not less than 10 nonapical stipital setae on right side; lamellae linguales each with 6 or 7 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 setae at hind edge of collum.

Body rings circular. Prozona smooth. Metazona with dense, regular, longitudinal striae reaching hind margin (14 or 15 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 and longer toward telson. Ozopores small, lying behind suture between pro- and metazona without touching it. Caudal dorsal projection of telson straight and long, 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; pads decreasing in size towards telson, totally disappearing on postfemur and remaining only on the tibial apex of hind legs. Claw of all legs at base with a very long (much longer than claw) setiform accessory claw ventrally ( Fig. 14 ). 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, but with one seta laterally (probably, the second seta (s) on the left is a deviation from the norm); tip ventrally very slightly rugose ( Fig. 15 ). Coxa 2 with one long mesapical oral seta (ao) clearly visible from the anterior surface and one short/thin mesapical oral seta (po) clearly visible just from the posterior surface (apex of po is only slightly visible in the anterior surface in Fig. 13 ) ( Figs 13, 16, 18 ), a gland opening positioned in central and axial position ( Fig. 13 ) according to Enghoff (1987). Penis slender, with an expanded basal part (a bit like an hourglass figure), about 1.9 × longer than wide ( Fig. 19 ). Ventral margin of body ring VII with lobes similar to figures 32, 33 in Enghoff (1987) (i.e. with ventrad subtriangular apically rounded lobes).

Gonopods slightly protruding. Anterior gonopod with parallel margins, apically strongly obliquely rounded, distal margins of the apical excavation sparingly papillate, rudimentary telopodite without seta ( Figs 20, 21 ). Flagellum slender, of medium length, probably (because poorly visible on the micropreparation), covered with cuticular spikes in the distal part. Posterior gonopods very slender ( Figs 22–24 ). Mesomeral process slightly arched forward, its apex (a) covered with papillae ( Figs 22, 24 ). Velum very steeply sloping, its margin evenly correctly arcuate, smooth, without a notch near the mesomeral process. Anterior surface of the mesomeral process with longitudinal shallow deepening (not visible in Fig. 22 ). Solenomere (sl) spinose, covered with spikes, mainly in front and apically ( Figs 22, 23 ).

Female. Length in alcohol about 40.0 mm, midbody vertical diameter about 3.5 mm, with 56(–1) rings, excluding telson. Caudal dorsal projection of telson shorter than one in male, covered with dense setae; curved dorsally claw-shaped process at tip smaller than one in male. Vulva as in Fig. 17 .

Etymology. The specific epithet refers to the arcuately curved velum edge. Adjective.

Remarks. Nepalmatoiulus arcuatus sp. nov. differs from N. pallidus mainly by the body coloration: marbled dark grey with a brown narrow transverse line on caudal margin of each metazonite (vs. yellow-grayish, with a narrow middorsal dark line and two broad lateral marbled brown stripes in N. pallidus ), by the perfectly arcuate margin of the velum (vs. not evenly, not perfectly arcuate margin in N. pallidus ), by the strongly obliquely rounded promere apex (vs. rectangular promere apex in N. pallidus ), by the absence of a notch of velum margin near the mesomeral process (vs. presence of a tiny notch in N. pallidus ), by a thinner and slenderer apex of the mesomeral process, by a poorly spinose solenomere: mainly in front and apically (vs. solenomere spinose throughout in N. pallidus ), by the subtrapezoidal smooth lobes of gnathochilarium mandibular stipites (vs. triangular lobes in N. pallidus ), by the penis almost as an hourglass figure (vs. subtrapezoidal in N. pallidus ), by the ventral pads on male legs gradual decreasing in size towards telson (vs. such pads not decreasing in size towards telson in N. pallidus ).

Figures

FIGURES 13–19. Nepalmatoiulus arcuatus sp. nov., male holotype (Figs 13–16, 18, 19) and female paratype (Fig. 17) (ZMUM). 13. Coxae 2, anterior view. 14. Claw of hind most leg. 15. Leg pair 1, anterior view. 16. Coxae 2, posterior view. 17. Vulva, posterior view. 18. Mesapical oral setae, posterior view. 19. Penis, posterior view. Abbreviations: ao, anterior mesapical oral seta; po, posterior mesapical oral seta; s, abnormal seta. Scales: 10 μm (Fig. 14), 20 μm (Figs 13, 16, 19), 30 μm (Fig. 15), 100 μm (Fig. 17).

FIGURES 20–24. Nepalmatoiulus arcuatus sp. nov., male holotype (ZMUM). 20. Left promere, posterior view. 21. Distal part of left promere, posterior view. 22. Opisthomere, mesal view. 23. Distal part of solenomere, mesal view. 24. Apex of mesomeral process. Abbreviations: a, apex; sl, solenomere. Scales: 2 μm (Figs 23, 24), 10 μm (Fig. 21), 100 μm (Figs 20, 22).