Brasilomma Brescovit, Ferreira & Rheims

Brescovit, Antonio Domingos, Ferreira, Rodrigo Lopes, Silva, Marconi Souza & Rheims, Cristina Anne, 2012, Brasilomma gen. nov., a new prodidomid genus from Brazil (Araneae, Prodidomidae), Zootaxa 3572, pp. 23-32 : 24-25

Genus Brasilomma Brescovit, Ferreira & Rheims gen. nov.

Etymology. The generic name is a contraction of Brazilian Lygromma , neuter in gender.

Type species: Brasilomma enigmatica sp. nov.

Diagnosis. Within Theuminae, Brasilomma gen. nov. is distinguished from other genera by the absence of clavate translucent setae on the abdominal dorsum (see Platnick et al. 2005: fig. 31). It further differs from Chileuma by the absence of eyes (species of Chileuma have six well developed eyes); from Chilongius by lacking their centrally situated epigynal atrium (see Platnick et al. 2005: figs 65, 69); from Tricongius by lacking the protruding chelicerae with relatively long fangs and modified cheliceral promargin (see Platnick & Höfer, 1990: 5) and from Lygromma by having a single long prong in the RTA, instead of two or more short ones (see Platnick & Shadab, 1976: figs 10, 14). It can be distinguished from the remaining South American prodidomids by the male palps with a large triangular projection, covering the base of the embolus ( Fig. 18 ) and by the distal border of the tegulum projected over the base of the conductor and median apophysis ( Figs 18–19 ).

The females are distinguished by the blind, posterior atrium ( Fig. 20 ) in the epigynum and by the anteriorly widened copulation ducts ( Fig. 21 ) arising from an internal, mushroom-shaped plate ( Fig. 22 ).

Description. Small spiders, total length 2.3–3.0. Prosoma ovate, narrowed anteriorly to slightly less than half its maximum width; surface covered with short, light, needle-like setae; thoracic groove short, longitudinal, on posterior third of prosoma. Eyes absent, with only a pair of vestigial whitish spots anteriorly ( Figs 1–2 ). Chelicerae vertical, not divergent; promargin not modified, with three pro and one retromarginal teeth in males; seven pro and five retromarginal denticles in females; fang longer than chelicerae width; chilum entire. Labium pentagonal, slightly wider than long, widest posteriorly. Endites rectangular, convergent anteriorly; serrula short and slightly curved. Sternum longer than wide, projected between coxae IV; surface smooth, with long, darkish setae along lateral margins. Legs covered with short, light, needle-like setae; leg formula 4123; trochanter smooth, without deep notch; metatarsi and tarsi without scopula; tarsi with two pectinate claws, I–II long toothed ( Fig. 6 ) and III–IV short toothed ( Fig. 8 ); specialized claw teeth and specialized setae at base of claws ( Figs 6–8 ); claw tufts composed of 4–5 widened spatulate setae ( Figs 6–8 ); trichobothria with deep ridges, 4–5 dorsal on metatarsi and 2–3 dorsoprolateral on all tarsi ( Fig. 1–2 ). Tarsal organ with elevated and rounded border ( Fig. 5 ). Opisthosoma oval, longer than wide, covered with short, light, needle-like setae and anteriorly with long, dark, posteriorly curved setae; colulus absent. Six spinnerets, anterior laterals elongated, not advanced anteriorly, widely separated ( Figs 13–15 ), bearing long major ampullate gland spigots, few piriform gland spigots and many accompanying setae ( Figs 9–10 , 13–14 ); posterior medians small, narrow, contiguous ( Figs 14–15 ); posterior laterals almost contiguous, with at least 3 aciniform gland spigots with narrow shaft, and at least two spigots with larger shafts, probably of cylindrical glands ( Figs 11–15 ). Male palp: tibia short, approximately half cymbium length, with single conical RTA, two strong, elongate setae prolaterally and one dorsally; cymbium ovate, without scopula and with two or three strong, dark setae; tegulum ovoid with distal triangular projection partially covering the embolus; embolus short and conical, arising prolaterally and gently curving retrolaterally towards laminar, hyaline conductor; median apophysis present, hook-shaped, slightly wider at base ( Figs 18–19 ). Epigynum wider than long with posterior, blind rounded depression ( Fig. 20 ); pair of copulation openings on internal mushroom-shaped, sclerotized plate ( Fig. 21 ); copulation ducts proximally wide and straight, distally narrowed and very convoluted; spermathecae indistinct; fertilization ducts short, hook-shaped and pointing away from each other ( Fig. 22 ).

Distribution. Known from three caves in the state of Minas Gerais, Brazil.

Composition. Monotipic.

Figures

FIGURE 1. Brasilomma enigmatica sp. nov. Immature, latero-dorsal habitus, collected in Moeda Sul cave (iron ore cave). Photo: R. L. Ferreira.

FIGURE 2. Brasilomma enigmatica sp. nov. Male, dorsal habitus, colleted in Bromélias cave (quartzite cave). Photo: R. L. Ferreira.

FIGURES 18 – 22. Brasilomma enigmatica sp. nov.: 18 – 19 male, left palp (18 ventral view, 19 retrolateral view); 20 – 22 female, epigynum (20 ventral view, 21 dorsal view, 22 posterior view). Scale lines: 0.25 mm.

FIGURES 3 – 8. Brasilomma enigmatica sp. nov., female: 3 Tarsus I, lateral view; 4 Trichobothria, dorsal view; 5 Tarsal organ, dorsal view; 6 – 7 Tarsus I, lateral view, showing specialized claw teeth (arrow); 8 Tarsus IV, lateral view, with same claw teeth (arrow). Scale lines: 0.25 mm.

FIGURES 13 – 17. Brasilomma enigmatica sp. nov., female: 13 – 15 Spinnerets, distal view; 16 – 17 tarsus, lateral view (16 tarsus I, 17 tarsus IV).

FIGURES 9 – 12. Brasilomma enigmatica sp. nov., female: 9 – 10 Anterior lateral spinnerets, distal view (thick arrows pointing to piriform gland spigots and thin arrows to plumose setae); 11 – 12 Posterior lateral spinnerets, distal view. Scale lines: 0.25 mm.