Acanthomegabunus altaicus, Tchemeris, A. N., 2015

Tchemeris, A. N., 2015, Taxonomic notes on Acanthomegabunus Tsurusaki, Tchemeris & Logunov 2000 (Arachnida: Opiliones: Phalangiidae), with a description of the new species A. altaicus sp. n. from the Altai Mountains of Russia and NE Kazakhstan, Zootaxa 3990 (4), pp. 567-574 : 569-574

Acanthomegabunus altaicus sp. nov.

Figs 2–4 , 6–13, 16 , Map 1

Type. Holotype ♂ ( SZM O.001.0173) from Kazakhstan, East Kazakhstan Area, Kurtchumskii Distr., SW Altai, junction of Kurtchumskii and Yuzhnyi Altai Mt. Ranges, Karakoba River, 1550 m a.s.l., [49°00'30'' N, 86°01'45'' E], 22.VI.1997, R. Yu. Dudko & V. K. Zinchenko.

Paratypes. KAZAKHSTAN: 1 ♂ ( SZM O.001.0174), East Kazakhstan Area, Katon-Karagaiskii Distr., SW Altai, W of Tarbagatai Mt. Range, Burkhat Pass, 2150 m a.s.l., 24.VI.1997, [49°07'30'' N, 86°01'24'' E], R. Yu. Dudko & V. K. Zinchenko. RUSSIA: 8 ♂ ( SZM O.001.0008), Kosh-Agatch Distr., Ukok Plateau, 2400–2500m a.s.l., near Muzdy-Bulak Lake, [49°28’N 87°65’E], 09.VII.2008, V. K. Zinchenko

Etymology. The species name originates from the type locality, the Altai ( Russia).

Diagnosis. Acanthomegabunus altaicus sp. n. is closest to A. sibiricus from the mountains of South Siberia (see Tsurusaki et al. 2000). The main diagnostic characters between these species are given in Table 1 .

MALE. Measurements. Body 3.63 long, 2.21 wide. Cephalothorax 1.24 long. Eye tubercle 0.50 wide. Clypeus length: 0.49. Chelicera: basal segment 1.01 long; distal segment 0.87 long; forceps 0.42 long. Penis 2.09 long, 0.32 wide at its base, glans 0.36 long. Length of palp segments: 1.11 + 0.56 + 0.52 + 1.08 = 3.27. Length of leg segments: I: 1.68 + 0.93 + 1.85 + 1.91 + 2.53 = 8.9; II: 3.36 + 0.98 + 3.03 + 2.87 + 4.22 = 14.46; III: 1.08 + 0.84 + 1.88 + 2.26 + 2.82 = 8.88; IV: 3.12 + 1.02 + 2.58 + 3.82 + 3.62 = 14.16.

Body as in Figs 2–4 . Dorsum smooth, except for the presence of some denticles. Opening of scent gland pores not conspicuous, but visible from above. Each abdominal tergite with transverse row of acute tubercles. Ocular tubercle ( Figs 2–4 ) huge but low, occupying about a half of the cephalothorax length at midline, crowned with short acute spines. Leg coxae sparsely covered with minute spine-tipped tubercles and setae. Abdominal sternites covered with scattered setae. Genital operculum only with minute setae.

Chelicera as in Figs 6–7 ; the first segment distodorsally with some spines, the second segment with a group of acute tubercles on its top, dorsally and distomesally with sparse setae.

Palp as in Figs 8–11 ; trochanter ventrally and dorsally with a few acute tubercles; femur distomesally with a hump covered with setae; ventrally and dorsally with prominent acute tubercles; patella distomesally with an apophysis densely covered with setae and dorsally and laterally with prominent acute tubercles; tibia dorsally with prominent acute tubercles, laterally and ventrally with longitudinal rows of 3–4 tubercles; tarsus curved on its ventral surface, ventromesally with an inconspicuous row of several denticles and scattered micro-denticles; claw smooth. Femur ectal surface with a group of 4–6 pores (presumably of glandular function) near the basal joint.

Legs relatively short. Legs I swollen and robust, remaining legs thin ( Figs 2–4 ). Each segment round or slightly pentagonal or hexagonal in cross section, with ridges along femora and patellae; tibiae with longitudinal rows of erected hair-tipped spines. Number of spines in the rows: Leg I - Fm = 6, Pt and Tb = 5; others legs Fm, Pt and Tb = 5. Metatarsus also dorsally with a single row of hair-tipped spines. Tibia proximally with a spiracle on its ectal surface. All metatarsi dorsally and mesally with rows of small spines, only metatarsus I mesally armed with scattered denticles.

Penis as in Figs 12–13 ; corpus gradually widening toward base, dorso-ventrally flattened at the distal half. Glans ( Fig. 16 ) bean-shaped, distally with two pairs of small spines.

Coloration: Carapace lighter than abdomen, light ochre, with brown and pale brown spots and patterns. Ocularium milk-ochre in dorsal view, laterally surrounded by a dark brown ring. Abdomen pale brown, with a distinct saddle. Venter creamy grey. Legs: Fm, Pa and Tb orange-brown, other segments yellow-ochre. Legs I darker than other legs. Palps and chelicerae orange-brown, with dark ochre patterns.

Variability: Individuals can differ in body length, limbs and the penis. Body 3.17–3.71 long. Penis 1.97–2.09 long. Length of palp: 2.98–3.37. Length of legs: I: 7.68–8.97; II: 13.64–14.57; III: 8.12–8.97; IV: 13.75–14.16. Specimens from Kosh-Agatch Distr. are darkest, with the predominance of black-brown colours.

FEMALE. Unknown.

Distribution. The SW Altai: Russia and Kazakhstan (Map 1).

Habitat. This species can be collected from moss-stony tundra, moss pebble banks of rivers, Abies forest, Anemone meadows and stony debris.

MAP 1. Distribution of Acanthomegabunus species: A. sibiricus (stars); A. altaicus sp.n. (Holotype—white cross, Paratypesblack crosses).

Figures

FIGURES 1 – 3. Males of Acanthomegabunus species. 1, A. sibiricus, lateral view; holotype of A. altaicus sp. n.; 2, lateral view; 3, dorsal view.

FIGURES 4 – 5. Lateral view of anterior part of male Acanthomegabunus: 4, A. altaicus sp. n.; 5, A. sibiricus.

FIGURES 6 – 11. Appendages of the male holotype of Acanthomegabunus altaicus sp. n.: 6, left chelicera, mesal view; 7, left chelicera, ectal view; 8, patella and tibia of left palp, dorsal view; 9, femur of left palp, posterior view; 10, left palp, mesal view; 11, left palp, ectal view.

FIGURES 12 – 17. Penes of Acanthomegabunus species. Holotype of A. altaicus sp. n.: 12, dorsal view; 13, lateral view. A. sibiricus: 14, dorsal view; 15, lateral view; 16, glans of A. altaicus sp. n.; 17, glans of A. sibiricus.

Tables

TABLE 1. Comparison of diagnostic features in Acanthomegabunus altaicus sp. nov. and A. sibiricu s.

	Acanthomegabunus altaicus sp. n.	Acanthomegabunus sibiricus
Chelicera	medium sized (Figs 6–7)	small (Tsurusaki et al. 2000: figs 2 E–F; 3A, D)
Leg I	swollen and robust (Figs 2–4)	thin (Figs 1, 5; Tsurusaki et al. 2000: figs 2A, C)
Оcularium	relatively low, with short acute spines (Figs 2–4)	Relatively high, with long acute spines (Figs 1, 5; Tsurusaki et al. 2000: figs 1A–C)
Penis	Corpus with a visibly widened base (Fig. 12); glans bean-shaped (Fig. 16).	Corpus not widened at its base (Fig. 14; Tsurusaki et al. 2000: figs 1J, 4A); glans seed-shaped (Fig. 17; Tsurusaki et al. 2000: figs 1K, 4B)