Micropholcus shaat Huber sp. nov.

Figs 4 C, 56, 57, 58, 59

Type material.

Holotype. Oman – Dhofar • ♂; Shaat sinkhole, in wadis leading to sinkhole; 16.774 ° N, 53.587 ° E; 850 m a. s. l.; 25 Feb. 2018; B. A. Huber leg.; ZFMK Ar 24676.

Other material.

Oman – Dhofar • 4 ♂♂, 2 ♀♀, 1 juv.; same collection data as for holotype; ZFMK Ar 24677 • 1 ♀, 1 juv.; same collection data as for holotype but 24 Feb. 2018; ZFMK Ar 24678 • 3 ♀♀, in pure ethanol; same collection data as for holotype but 24–25 Feb. 2018; ZFMK Om 137 .

Diagnosis.

Males are easily distinguished from known congeners by several details of male palp (Figs 56, 57; proximal process on trochanter; slender femur without distinct processes; procursus with simple dorsal hinged process; prolateral sclerite on genital bulb simple and slender). Females are easily distinguished from known congeners by anterior position of epigynal ‘ knob’ (Fig. 58 C), by distinctive sclerotised band medially on epigynal plate (Fig. 59 A), and by presence of large membranous sac in internal genitalia (Fig. 59 D); from geographically close M. darbat sp. nov. also by larger and wider pore plates (Fig. 58 C).

Description.

Male (holotype). Measurements. Total body length 2.6, carapace width 0.9. Distance PME - PME 260 µm; diameter PME 85 µm; distance PME - ALE 15 µm; distance AME - AME 20 µm; diameter AME 45 µm. Leg 1: 27.3 (6.8 + 0.5 + 6.9 + 11.7 + 1.4), tibia 2: 4.3, tibia 3: 2.6, tibia 4: 3.6; tibia 1 L / d: 81; diameters of leg femora (at half length) 0.09–0.10; of leg tibiae 0.08–0.09.

Colour (in ethanol). Prosoma and legs ochre-yellow, carapace with brown median mark; leg femora 1 and 2 proximally darkened; legs with darkened patellae and tibia-metatarsus joints; abdomen pale ochre-grey.

Body. Habitus as in Fig. 4 C. Ocular area raised (distinct in frontal view). Carapace without thoracic groove. Clypeus unmodified. Sternum wider than long (0.65 / 0.50), unmodified. Abdomen oval, approximately twice as long as wide.

Chelicerae. As in Fig. 58 A, B; with pair of distal apophyses near laminae, each with two cone-shaped hairs; pair of lateral, indistinct, weakly sclerotised humps; and pair of distinct proximal frontal apophyses.

Palps. As in Fig. 56; coxa unmodified; trochanter with long ventral apophysis with distinct proximal process directed towards coxa; femur slender, distally widened, with indistinct ventral hump at half length; femur-patella joints shifted toward prolateral side; tibia-tarsus joints shifted toward retrolateral side; tarsus with large tarsal organ. Procursus (Fig. 57 A – C) proximally with sclerotised prolateral hump; at half length with prolateral sclerotised ridge transforming distally into transparent membrane, and brush of dorsal hairs; distally with small retrolateral ridge, bifid membranous ventral-prolateral flap, and distinctive dorsal hinged process. Genital bulb (Fig. 57 D, E) with strong proximal sclerite, prolateral process simple and slender, and short embolus proximally sclerotised, distally with transparent extensions.

Legs. Without spines, without curved hairs, without sexually dimorphic short vertical hairs; retrolateral trichobothrium of tibia 1 at 6 %; prolateral trichobothrium absent on tibia 1; tarsus 1 with> 25 pseudosegments, distally distinct.

Variation (male). Tibia 1 in five males (incl. holotype): 6.2–7.8 (mean 6.8). Distance between eye triads 250–270 µm. Some males with white marks dorsally on abdomen.

Female. In general very similar to male but abdomen often wider, ocular area slightly less raised and triads closer together (PME - PME 200 µm). Tibia 1 in five females: 5.2–5.6 (mean 5.3). Epigynum (Fig. 59 A) anterior plate roundish, anterior margin weakly curved, posterior margin strongly curved, with distinctive median sclerotised band, membranous knob at anterior end of sclerotised band, directed towards posterior; lateral internal sclerites clearly visible in untreated specimens; posterior epigynal plate very short and indistinct. Internal genitalia (Figs 58 C, 59 B – E) with pair of large sclerotised pore plates, with roughly square-shaped sclerotised opening leading into large round membranous sac (collapsed in Fig. 59 D; removed in Fig. 59 B, C, E); with complex system of lateral membranous structures.

Etymology.

The species name is derived from the type locality; noun in apposition.

Distribution.

Known from type locality only, in Dhofar, western Oman (Fig. 13 C).

Natural history.

The spiders were found in niches and small caverns in the walls of the wadis leading to Shaat sinkhole (Fig. 14 E). They rested in the apex of very fine and poorly visible dome-shaped webs directly on the rock surface.