Acanthomegabunus Tsurusaki, Tchemeris & Logunov, 2000

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 : 568

Genus Acanthomegabunus Tsurusaki, Tchemeris & Logunov, 2000

Type species. Acanthomegabunus sibiricus Tsurusaki, Tchemeris & Logunov 2000 ; designated by monotypy.

Diagnosis. Most similar to Megabunus Meade 1855 from western Europe ( Martens 1978), but distinguished by the following characters: 1) absence of long ventral spines on the palpal trochanter ( Tsurusaki et al. 2000: fig. 3B–C); 2) presence of a dorsal row of conspicuous spines on palpal patellae ( Tsurusaki et al. 2000: fig. 3B–C; Figs. 1–2 , 4–5 , 10–11 ); and 3) all legs with five to six longitudinal rows of erect spines ( Tsurusaki et al. 2000: fig. 2A–C; Figs 1–5 ).

Description. Medium-sized opilionids, with soft or, rarely, rigid integument, body smooth except for a transverse row of several minute tubercles on each abdominal tergite and a few scattered teeth on the cephalothorax. Ocular tubercle huge, with numerous long spines ( Figs 1–5 ).

Chelicera normal, without a ventral tooth on its basal joint; movable finger without apophysis ( Figs 6–7 ). Supracheliceral lamellae not developed, invisible from above. Scent gland pores visible from above ( Figs 1–3 ).

Palpi ( Figs 1–5 , 10–11 ) with distomesal apophyses on patellae and tibiae; femora distomesally with a knoblike process bearing several bristles, femora distomesally with a hump, ectal surface of femur with a group of 4–6 pores (presumably of glandular function) near the basal joint; male tarsi with a ventromesal row of denticles (unarmed in females A. sibiricus , female unknown in A. altaicus sp. nov.); femora to tibiae dorsolaterally and ventrally with three rows of conspicuous spines; palpal claw untoothed.

Legs relatively short; trochanter to metatarsus with one row (metatarsi) or five longitudinal rows (femur to tibiae) of erect spines. Penis dorso-ventrally flattened, a bundle of muscles occupying basal one-third to two-thirds length of corpus ( Figs. 12, 14 ).

Composition. Two species: Acanthomegabunus sibiricus and A. altaicus sp. nov., both are known from the mountains of South Siberia, Russia.

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.