Cueva de la Pileta (La Pileta Cave), 36°41'28.51"N, 5°16'11.66"W, 724 m a.s.l, Sierra de Grazalema, Benaoján, Málaga, Andalusia, Spain.

Holotype. ♂: Spain: “ESP. Málaga, Benaoján / Cueva de la Pileta, 04-26-2013 / 36°41'28.51"N; 5°16'11.66"W, 724 m a.s.l. / F. Fadrique leg”, (MCNB).

Paratypes : 1 ♀: same data as holotype, (MCNB); 1 ♀: “ESP. Málaga, Benaoján / Cueva de la Pileta, 06-08-2015 / Sierra de Grazalema-Ronda / 36°41'28.51"N; 5°16'11.66"W, 724 m a.s.l. / T. Pérez leg.”, (CCH).

We dedicate this new species to the Bullón family, historical owners of the Cueva de La Pileta.

Habitus as in Fig. 1. Body length: 2.13 mm. Apterous and microphtalmic, with only three omatidia (probably non-functional eyes). Entirely pale brown with lighter maxillary palpi and tarses. Body (specially the head) and appendages (antennae, maxillary palpi and legs) extraordinary elongated and slender. Pubescence of the dorsal surface consist of short suberect white setae on head, pronotum, elytra and abdomen, pubescence on the ventral surface consists of very dense clusters of tomentose setae on the head, mesoventrite and first visible sternite, and short, suberect, white setae on the metaventrite and sternites, other suberect shorter setae on antennae and legs.

Figures 1–2. 

Geopselaphus bullonorum Hernando & Castro, sp. nov. Habitus in dorsal view 1 male 2 female.

Head : (Figs 3, 4) total length (0.64 mm), maximum width (0.17 mm). Extraordinarily elongate, 3.5 times longer than wide, clearly narrower than pronotum. Frons broadly grooved and distally bilobed, narrow and shallow longitudinal groove starts between both lobes, which extends back to level of eyes. Dorsolateral part with two longitudinal and parallel carinae, clearly higher in supra-ocular area and attenuated backwards, with tomentose fossae very small. Surface entirely microreticulated, dorsal pubescence composed of few short, white, semi-erect setae arranged in pair of lateral longitudinal series. In lateral view (Fig. 4), dorsal part practically flat in its anterior part, barely gibbous and slightly narrowed at posterior part. Gular protuberance projecting backward and hook-shaped (Fig. 4). Tomentose pubescence of ventral part, short and sparse, extending from gular protuberance to basal narrowing (Figs 8, 9). Eyes reduced, with only three unpigmented ommatidia, likely not functional (Fig. 3). Antennae (Fig. 5) extraordinarily long (1.57 mm) and slender, exceeding the posterior margin of elytra when bent backwards, scape cylindrical and parallel-sided, 3.2 times longer (0.28 mm) than wide (0.04 mm), pedicel cylindrical and subparallel-sided, 1.3 times longer (0.08 mm) than wide (0.04 mm), antennomeres 3–7 cylindrical, equal in length and longer (0.11 mm) than wide (0.04 mm); antennomere 8 cylindrical, with equal width, but shorter (0.06 mm) than previous five; antennomeres 9–10 cylindrical, both very similar in length and shape, wider and twice as long as previous six antennomeres; terminal antennomere very long (0.37 mm) and club-shaped, slightly asymmetrical at apex and with equal length as three previous antennomeres together. Maxillary palps extraordinarily long (1.57 mm) and slender (Fig. 5), palpomere 1 filiform, slightly curved; palpomere 2 very long (0.48 mm), filiform over practically its entire length and abruptly widened at its apical end; palpomere 3 very short and conical; palpomere 4 very long (0.73 mm), slightly arched, filiform throughout practically its entire length, progressively thickening at apex, which is club-shaped and with surface of thickened part completely covered with granules and very fine and erect pubescence.

Figures 3–7. 

Geopselaphus bullonorum Hernando & Castro, sp. nov. head 3 dorsal view 4 lateral view. Head appendages 5A antennae 5B maxilar palpi. Elytra and abdomen in dorsal view 6 male 7 female.

Pronotum : Longer (0.32 mm) than wide (0.24 mm) with subparallel sides, with the anterior and posterior margins straight, the latter finely bordered, surface smooth and shiny and with two dorsal longitudinal series of setae, each consisting of 4–5 white and semi-erect setae.

Elytra : Strongly narrowed at base, practically as long (0.6 mm) as wide (0.62 mm); each elytron with three basal foveae; humeral carinae entire and well-marked, each elytron with raised, entire and well-apparent discal carinae (Figs 6, 7), with entire sutural stria; surface smooth and shiny, the pubescence on each elytron composed of three series of white and semi-erect setae, two located along the two carinae and a third very short series on the discal surface, with the posterior margins of each elytron decorated by transverse series of semi-erect setae widely spaced and on same edge with dense fringe of tomentose setae (Fig. 6).

Ventral part : Mesoventrite with two very dense clusters of tomentose setae (Fig. 8), metaventrite convex, smooth and shiny and with some widely scattered semi-erect setae (Fig. 8).

Abdomen : With tergite IV (first visible tergite) very large, clearly wider (0.71 mm) than long (0.51 mm), shorter than the elytra and clearly wider than these, with a smooth and shiny surface and series of semi-erect setae along entire posterior margin. Sternite III (first visible sternite) with a broad transverse fringe of tomentose hairs that occupies entire basal part and with a long tuft of erect setae in central part of posterior margin (Fig. 8).

Figures 8–12. 

Geopselaphus bullonorum Hernando & Castro, sp. nov. Ventral part 8 male 9 female. Aedeagus 10–11 dorsal vision 12 lateral vision.

Male genitalia : Median lobe strongly acuminate at apex (Figs 10, 11) and in lateral view with the apex curved inwards (Fig. 12), internal sac with two fascicles of small spines (Fig. 11) and apical structure formed by modified spines of squamiform shape.

Female: General appearance similar to male (Fig. 2), but with posterior margin of the elytra with the fringe of tomentose setae broadest and more developed (Fig. 7), tergite IV clearly longer (0.55 mm), practically as long as length of elytra (Fig. 7), sternite III longer, without tuft of erect setae and rugulose at the base (Fig. 9).

The new species is well distinguished from the rest of the known species of the genus by its marked troglomorphism, such as the reduction of the eyes (only three unpigmented ommatidia) and an extraordinary general elongation of the body (especially of the head) and appendages (antennae, maxillary palps and legs). It is also characterised by the small size of the tomentose foveae on the head, which are large in the rest of the known species, the elytra have a complete dorsal carina (Figs 6, 7), which is absent or slightly elevated in the rest of the known species of the genus, and the aedeagus is quite different (Figs 10–12). It has also been compared with its geographical neighbour Geopselaphus longulus Besuchet, 1961, an endogean species showing some elongation of the head and palps, but always in comparison with the other endogean species and without any comparison with the new species.

Based on the aedeagus, Geopselaphus bullonorum seems to be close to Geopselaphus sencieri (Coquerel, 1858), distributed in Algeria, Morocco and the extreme south of the Iberian Peninsula (Jeannel 1956), both species have an acuminate median lobe, and the internal sac is very similar, consisting of two fascicles of spines (see Besuchet 1961).

So far, only known from the typical locality.

The Cueva de la Pileta has a total length of 2.406 m and a maximum slope of 102 m. All the specimens were captured wandering on walls in the sector called “La Gran Sima”, which is in one of the deepest parts of the cave, approximately 400 m from the cave entrance. This cave harbours a rich community of terrestrial subterranean arthropods, 32 species have been recorded so far (Pérez et al. 2013; Pérez and Aguilera 2014; Miralles and Pérez 2015), of which 12 are exclusively troglobitic. Six of them have a relatively wide distribution: Iberoniscus breuili Vandel, 1952, Trichoniscus gordoni Vandel, 1955 (Isopoda); Lithobius motasi Matic, 1967 (Lithobiomorphae); Tegenaria herculea Fage, 1931, Troglohyphantes furcifer (Simon, 1884) (Araneae) and Laemostemus lederi (Schaufuss, 1865), Trechus breuili Jeannel, 1913, Speonemadus bolivari (Jeannel, 1922) (Coleoptera); two species have a very restricted distribution and are only known from the Cueva de la Pileta and from some other caves in the same geographic area: Cryptops longicornis Ribaut, 1915 (Scolopendromorpha) and Dysdera bicornis Fage, 1931 (Araneae) and finally, with the new species describe here, four endemic species are known from Cueva de la Pileta: Baeticoniscus bulloni Garcia, Miralles-Núñez & Pérez, 2020 (Isopoda); Glomeris (Stenopleuromeris) albida Mauriès & Vicente, 1977 (Glomerida); Occidenchthonius bullonorum (Caravajal, García Carrillo & Rodríguez Fernández, 2012) (Pseudoscorpiones) and Geopselaphus bullonorum sp. nov.