Alpioniscus onnisi Taiti & Argano

Taiti, Stefano, Argano, Roberto, Marcia, Paolo, Scarpa, Fabio, Sanna, Daria & Casu, Marco, 2018, The genus Alpioniscus Racovitza, 1908 in Sardinia: taxonomy and natural history (Isopoda, Oniscidea, Trichoniscidae), ZooKeys 801, pp. 229-263: 229

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Alpioniscus onnisi Taiti & Argano

sp. n.

Alpioniscus onnisi Taiti & Argano  sp. n. Figs 5, 6, 7, 8, 18, 19

Alpioniscus fragilis  ; Taiti and Argano 2011: 167 (partim: Grotta del Caprone Tyson).

Material examined.

Prov. Cagliari: Holotype: ♂ (MZUF 9817), Grotta Giuanniccu Mene, c.n. 735 Sa/CA, 39°31'32.3"N, 9°36'08.9"E, Monte Castello di Quirra, Villaputzu 20.IV.2012, leg. C. Onnis, S. Taiti, R. Argano. Paratypes: many ♂♂ and ♀♀ (MZUF 9817), same data as holotype; 1 ♀ (MZUF 9818), same locality, 8.I.2011, leg. C. Onnis; 4 ♂♂, 15 ♀♀, 2 juvs (MZUF 9819), same locality, 20.IV.2013, leg. C. Onnis, R. Argano and S. Taiti; 2 ♂♂, 4 juvs (MZUF 9820), same locality, 16.III.2012, leg. C. Onnis; 2 ♂♂, 7 ♀♀ (MZUF 9821), Grotta del Caprone Tyson, n.c.n., Monte del Castello di Quirra, Villaputzu, I.1999, leg. G. Marini; 1 ♂ juv. (MZUF 9822), “Prisoni” Ipogean Tomb, 39°31'24"N, 9°36'26"E, 15 m, Monte del Castello di Quirra, Villaputzu, 20.IV.2012, leg. C. Onnis, R. Argano and S. Taiti.


Maximum length: ♂, 7.5 mm; ♀, 9 mm. Colourless body, outline as in Fig. 5A. Dorsal surface smooth with lanceolate scale-setae as in Fig. 5B. Many gland pores on lateral margins of pleonites 4 and 5, telson and lateral surface of uropodal protopod (Fig. 5E). Cephalon (Fig. 5C, D) with suprantennal line medially blunt; antennal lobes quadrangular obliquely directed outwards with concave dorsal surface. Eyes absent. Posterior margin of pereonite 1-3 straight, and of pereonites 4-7 progressively more concave (Fig. 5A). Pleonites 3-5 with reduced posterior points (Fig. 5A, E). Telson (Fig. 5E) more than twice as wide as long; distal part triangular with concave sides and rounded apex. Antennula (Fig. 5F) with second article distinctly shorter than first and third; third article distally enlarged and bearing approx. ten apical aesthetascs. Antenna (Fig. 5G) with fifth article slightly longer than flagellum; flagellum of ten articles with four groups of aesthetascs. Mouth parts (Fig. 6A-E) as in A. fragilis  . Pereopods with setose dactylar seta distally bifid, pereopod 7 with well developed water conducting system consisting of a groove with scales on basis, and lines of scales on ischium and merus. Uropod (Fig. 5E) with endopod distinctly shorter than exopod, endopod inserted proximally to exopod.

Male. Pereopod 1-4 (Fig. 7A) with carpus and merus bearing short scales on sternal margin. Pereopod 7 (Fig. 7B) ischium with straight sternal margin covered with short setae; merus with three lobes proximally. Genital papilla (Fig. 7C) with a rounded tip. Pleopod 1 (Fig. 7C) exopod triangular with acute apex; endopod enlarged at base, distal part narrow with almost parallel sides and bearing an apical seta. Pleopod 2 (Fig. 7D) exopod triangular with convex outer margin and a small apical seta; endopod with first article nearly twice as long as second, second article with a strong seta subapically cleft. Pleopod 3-5 exopods with a short apical seta (Fig. 8 A–C).


The new species is named after our Sardinian friend Carlo Onnis for his enthusiastic and efficient activity in collecting subterranean fauna, including part of the material treated here.


Alpioniscus onnisi  sp. n. is very similar to A. fragilis  and A. thanit  . It differs from the former in the smooth instead of granulated dorsal surface, the shape of the dorsal scale-setae, telson with triangular instead of trapezoidal distal part, and the male pleopod 2 endopod lacking a subapical lobe; from the latter mainly in the larger body shape and the male pleopod 1 exopod with slightly convex, instead of concave, medial margin, and shorter distal part.