Chthonius marciai Gardini 2021, n. sp.

Chthonius marciai n. sp.

(Figs 312–319, 410)

Type locality: Italy, Sardinia, Nuoro Province, Dorgali, Grotta del Bue Marino 12 Sa / NU (40°14’48”N, 9°37’22”E).

Distribution. Italy (Sardinia).

Diagnosis (♂). An anophthalmic hypogean Chthonius that differs from other species of the ischnocheles group in the following combination of characters: anterior margin of carapace without preocular microsetae; posterior margin of carapace with 2 macrosetae and 1 or 2 lateral microsetae; tergites I–II with 2 setae; chelicerae without lateral microsetae; chela 8.0 times as long as deep; chela length 1.52 mm; movable chelal finger length 1.08 mm; chelal fingers with contiguous teeth; fixed chelal finger with 86 teeth; ratio of pedipalpal femur/carapace 1.9.

Type material. ITALY — Sardinia: 1 ♂ (holotype), Nuoro Prov., Dorgali, Grotta del Bue Marino 12 Sa / NU (40°14’48”N, 9°37’22”E), 0 m a.s.l., 3. VI.2007, P. Marcia leg. (MHNG).

Derivatio nominis. Named after the collector of the holotype, Dr Paolo Marcia (University of Sassari), in recognition of his contribution to the knowledge of the subterranean fauna of Sardinia.

Description of adults (♂; ♀ unknown). Highly specialized troglomorphic facies; integument slightly pigmented, carapace, tergites, chelicerae and pedipalps pale brown; weak hispid granulation on cheliceral palm. Carapace (Fig. 313) 0.95 times longer than broad, trapezoidal, constricted posteriorly; anterior margin denticulate between median macrosetae, with a prominent epistome (Fig. 312); ocular area as in fig. 313, no eyes or eye-spots; chaetotaxy 4:6:4:2:m 2mm (21), setae long and thin, length of anteromedian macrosetae 0.18 mm. Chaetotaxy of tergites 2:2:4:4:6:6:6:6:1T2T1:4:1T2T1:0. Chaetotaxy of sternites 9:(3)11(3):(2)6(2):8:6:6:6:6:2T2T2:0:2; genital opening flanked by 12 setae on each side, partly scattered. Chelicerae (Fig. 314) 2.5 times as long as broad, palm with 6 setae, without lateral microsetae; fixed finger with 2 distal large teeth followed by 13 small teeth proximally increasingly reduced; movable finger with an isolated subapical tooth (di) at level with the spinneret, followed by a large tooth and 12 teeth proximally reduced in size; gs ratio 0.61; spinneret weakly raised, large and rounded; rallum with 11 blades; serrulae interior and exterior with 14 and 15 blades respectively. Coxal setae: pedipalp 5 (including 2 on manducatory process), I 3 + 3 marginal microsetae, II 4 and 5, III 6, IV 7; coxa II with 10 and 12 coxal spines, coxa III with 5 and 7 coxal spines; intercoxal tubercle bisetose. Pedipalp: femur 7.9 times as long as broad, femoral chaetotaxy 3:6:2:5:1; chela (Fig. 316) 8.0 times as long as deep; hand of chela 2.35 times as long as deep, with parallel sides in dorsal view (Fig. 315); fixed chelal finger with 86 contiguous teeth: 63 distal teeth cuspidate and slightly inclined backwards, 15 low and rounded teeth increasingly reduced towards trichobothrium sb and 8 proximal teeth recognizable only by the presence of dental canal (Figs 317–319), all teeth with dental canal; fixed finger at level of est-it with 8 teeth occupying 0.1 mm, distance between successive apices 0.0115 mm; tip of fixed chelal finger with apical sensilla af 1- 2 , distal paraxial seta gradually curved and thin; movable chelal finger with 75 teeth: distal half of the finger with 42 more widely spaced teeth, slightly scalene triangle-shaped, reclined and apically pointed; proximal half of the finger with 33 teeth that are apically rounded and increasingly reduced towards finger base, reaching back near b (between sb and b they are mainly recognizable only by the presence of dental canal) (Figs 317–319); movable finger at level of st-t with 7 teeth occupying 0.1 mm, distance between successive apices 0.014 mm; coupled sensilla pc just distad of sb; tip of movable chelal finger with apical sensilla am 1- 2 ; trichobothria as in fig. 316; ratio sb -st/sb -b = 1.6; ratio of movable finger/hand of chela 2.4; ratio of pedipalpal femur/movable finger 0.95; ratio of pedipalpal femur/carapace 1.9.

Measurements (in mm). Body length 1.5 (opisthosoma moderately shrunk). Carapace 0.54 × 0.57 (0.56 anteriorly). Chelicerae 0.64 × 0.25; movable finger length 0.33. Pedipalp: femur 1.03 × 0.13; chela 1.52 × 0.19; hand length 0.45; movable finger length 1.08.

Remarks. Among the western Mediterranean species of Chthonius with contiguous chelal teeth, none has the combination of characters shown by C. marciai n. sp.: anterior margin of carapace without preocular microsetae, posterior margin of carapace with 2 macrosetae and 1 or 2 lateral microsetae, tergites I–II each with 2 setae and chelicerae without lateral microsetae. Among the species with troglomorphic facies, Chthonius marciai is comparable to C. sp. cf lucifugus Mahnert, 1977 from the Rendez-vous de chasse Cave (Hérault, France) (Leclerc 1983) which has no preocular microsetae, tergites I–II with 2 and 4 setae and chelicerae without lateral microsetae, but the latter has 2 macrosetae on the posterior margin of carapace and no lateral microsetae.

Chthonius marciai could be related to the halophilic C. halberti, a Mediterranean–Atlantic species also present in Sardinia that has no preocular microsetae, the posterior margin of carapace with a variable number of setae (5 to 8), the chelicerae without lateral microsetae, but tergites I–II with 4 or more setae. Evident adaptive characters differentiate the two species.