Ikuma Lawrence, 1938

Zonstein, Sergei & Marusik, Yuri M., 2022, Redescription of the poorly known genus Ikuma Lawrence, with synonymy and description of a new species from Namibia (Araneae, Palpimanidae), African Invertebrates 63 (2), pp. 105-119 : 105

Genus Ikuma Lawrence, 1938

Ikuma Lawrence, 1938: 217.

Type species.

Palpimanus spiculosus Lawrence, 1927, by original designation.

Emended diagnosis.

Ikuma (I.) well differs from Palpimanus (P.) in the shape of the carapace (anteriorly narrowed, ovoidal and gently elevated from the edges to the domed central part in I. vs. round-oval and steeply edged in P.), in the clypeus (inclined in I., vertical in P.), and in the shape of the sternum (longer and visually narrower, ending posteriorly behind coxae IV in I. vs. shorter, looking subrounded, and ending posteriorly at the axes of coxae IV in P.). The whitish adpressed pubescence on the dorsal and lateral surface of the carapace is much longer and denser in I. (where it is present also on the dorsal abdomen) than in P. (where a similar pubescence is much shorter and sparser, and confined only to the carapace). The embolus is small, fragile and membranous in I. vs. relatively large, branched and with partially sclerotized structures in P. The adult females of these genera can be distinguished by the structure of the endogyne, either possessing (P.) or lacking (I.) heavily sclerotized parts.

Redescription.

Medium-sized to large palpimanids with carapace length ranging 4.4-5.8 in adult specimens. Dorsal body (both carapace and abdomen) densely covered with pale adpressed pubescence (Figs 1 , 2 ); most sclerotized parts (carapace, chelicerae, sternum and abdominal scuta) finely granulated, as in Figs 1 - 4 , 5A, B . Carapace (Figs 1C , 3A, B ) narrowed anteriorly, ovoidal, with raised central part gently sloping toward edges and elevated hump between eye group and thoracic fovea. Short T-shaped thoracic fovea deeply excavated, foveal sulci poorly discernible. Clypeus moderately long. Eight eyes (Figs 1C , 3 ); AME largest, other eyes relatively smaller and subequal in size. AER recurved; PER nearly straight and noticeably wider than AER; both rows form wide trapezoidal figure. MOQ slightly wider than long. Chilum inconspicuous. Chelicerae about twice longer than clypeus; stridulatory ridges absent; cheliceral fang serrated; cheliceral furrow armed with several (5-6 in Ikuma larseni sp. nov.) peg teeth. Maxillae triangular. Labium long and narrow, notched anteriorly (Fig. 4B ). Sternum densely granulated, covered with fine short hairs and extending backward between coxae IV (Figs 1D , 4A, D ).

Palps short, legs I-IV moderately long. Leg formula: 4132. Leg I robust, with considerably swollen and laterally flattened femur, with patella longer that tibia, and tarsus longer than metatarsus (Figs 1B , 2B, D ). Tibia and metatarsus I with wide and dense prolateral scopula. Leg tarsi II-IV relatively short; two tarsal claws narrow and provided with several short teeth. Claw tufts well-developed (as in Fig. 7A ).

Abdomen fusiform, in unsclerotised part with contrasting dorsal pattern or uniformly pale coloured. Abdominal scuta conforming a rather short pedicel tube; dorsal portion of scutum narrow, small and narrowly separated from both pedicel tube and large scoop-like ventral portion. Small spinneret group set on low mound (see Fig. 7B ). AMS small, cylindrical, two-segmented; PMS and PLS reduced to a few sessile spigots in females and absent in males.

Composition.

Ikuma includes two species: I. spiculosa (Lawrence, 1927) and I. larseni sp. nov.

Distribution.

The genus is currently known only from Namibia.

Figures

Figure 1. Ikuma spiculosa, immature holotype specimen SAM-ENW-B 006293 A, B spider in dorsal and lateral view, respectively C carapace, dorsal D body, ventral. Scale bars: 1 mm.

Figure 2. Ikuma larseni sp. n., holotype female NMSA-SPI- 26895 (A, C) and paratype male NMSA-SPI- 26894 (B, D) A, B spider in dorsal view C, D same, lateral. Scale bars: 5 mm.

Figure 3. Ikuma larseni sp. n., holotype female NMSA-SPI- 26895 (A, C, D) and paratype male NMSA-SPI- 26894 (B, E) A, B carapace in dorsal view C, E eye group, clypeus and chelicerae, dorsal D same, lateral. Scale bars: 1 mm (A, D); 0.5 mm (B, C, E).

Figure 4. Ikuma larseni sp. n., holotype female NMSA-SPI- 26895 (A, C, D) and paratype male NMSA-SPI- 26894 (B, E) A, B cephalothorax and basal abdomen in ventral view C chelicerae, labium and maxillae, ventral D, E pedicel and abdominal scuta, ventral. Abbreviations: Eg epigastral plate; Le lateral extensions of scutum; Ln labial notch; Ps postgastral scuta. Scale bars: 1 mm (A, D); 0.5 mm (B, C, E).

Figure 5. Ikuma larseni sp. n., paratype female NMSA-SPI- 26881 A, B dissected, macerated and Chlorazol-tinted abdominal scuta in dorsal and ventral view, respectively C-F structures of endogyne, dorsal (inside). Abbreviations: Ds dorsal scutum; Eg epigastral plate; Ft fine threads; Gg grape shaped glands; La lateral apophyse of endogynal fold; Le lateral extensions of scutum; Pt petiolar tube; Rf basolateral fold of endogyne; Rs membranous sac like part of receptacle. Scale bars: 0.5 mm (A, B); 0.25 mm (C, D); 0.1 mm (E, F).

Figure 7. Ikuma larseni sp. n., holotype female NMSA-SPI- 26895 (A, B) and paratype male NMSA-SPI- 26894 (C, D) A tarsus IV in retrolateral view B spinnerets, ventral C entire leg II, retrolateral D palpal segments from patella to cymbium, retrolateral. Scale bars: 0.5 mm (A, D); 0.25 mm (B); 1 mm (C).