Xenonychus Wollaston, 1864

Lackner, Tomáš, 2010, Review of the Palaearctic genera of Saprininae (Coleoptera: Histeridae), Acta Entomologica Musei Nationalis Pragae (suppl.) 50, pp. 1-254 : 225

Xenonychus Wollaston, 1864

Xenonychus Wollaston, 1864: 179 . Type species: Xenonychus fossor Wollaston, 1864 (= Saprinus tridens Jacquelin- Duval, 1852), by monotypy.

Xenonychus: MARSEUL (1864) : 358; SCHMIDT (1887): 354; GANGLBAUER (1899): 394; REITTER (1910): 13 (partim); BICKHARDT (1913): 32; BICKHARDT (1916 –1917): 81, 102 (partim); REICHARDT (1925): 137; REICHARDT (1926): 14; REICHARDT (1941): 156, 334; PEYERIMHOFF (1936): 227; KRYZHANOVSKIJ & REICHARDT (1976): 112, 242; VIENNA (1980): 115, 198; MAZUR (1984): 108; MAZUR (1997): 267; YÉLAMOS (2002): 245, 340; MAZUR (2004): 101.

Diagnosis. Cuticle dark brown with bronze to greenish hue; frontal disc smooth or laterally with vaguely impressed rugae, frontal stria straight or slightly curved outwardly (occasionally interrupted); eyes flattened, invisible from above. Pronotal foveae absent, disc shallowly punctate; pronotal hypomeron setose; dorsal elytral striae 1–4 almost reaching elytral apex; elytral epipleuron setose. Pre-apical foveae large and deep, both sets of prosternal striae present; lateral discs of ventrites and all visible abdominal sternites setose. Outer margin of protibia with three large distal triangular teeth topped with large triangular rounded denticle, followed by 5 short proximal denticles; claws of meso- and metatarsomeres long, almost straight.

Differential diagnosis. Xenonychus is the only genus of the Palaearctic Saprininae that has almost complete dorsal elytral striae 1–4, stopping short of elytral apex. Judging from its general appearance it could be confused with the genera Chivaenius or Exaesiopus , but differs from them by the almost complete dorsal elytral striae; furthermore it differs from Chivaenius by the present, well developed pre-apical foveae (absent in Chivaenius ), setose elytral epipleuron (glabrous in Chivaenius ) as well as the differently shaped prosternum (knife-like, strongly compressed in Chivaenius ) and the differently shaped protibia. From Exaesiopus it likewise differs by the length of dorsal elytral striae, as well as by the shape of protibia, frontal disc (with elongate rugae in Exaesiopus and almost glabrous in Xenonychus ) and the glabrous elytral epipleuron.

Biology. Both species of the genus Xenonychus are typical inhabitants of the desert areas and shifting sands, often found on carrion, usually together with the other psammophilous Saprininae (Lackner, pers. observ.).

Distribution. This genus has two Palaearctic representatives: Xenonychus tridens (Jacquelin- Duval, 1852) distributed from the Cape Verde Archipelago and Canary Islands through the Sahara Belt along the Mediterranean coasts as far as the Arabian Peninsula; and X. aralocaspius Kryzhanovskij, 1976 in KRYZHANOVSKIJ & REICHARDT (1976) , occurring around the Caspian and Aral Seas ( KRYZHANOVSKIJ & REICHARDT 1976, MAZUR 1997).

Species examined. Xenonychus aralocaspius Kryzhanovskij, 1976 ; Xenonychus tridens ( Jacquelin-Duval, 1852) .

Discussion. This taxon is probably sister to the most derived ‘grade’ of Palaearctic Saprininae : genera Philothis and Ctenophilothis as indicated by the results of the preliminary cladistic analysis (LACKNER, in prep.). It is probably a monophyletic taxon supported by several putative synapomorphies: almost complete dorsal elytral striae, large, well-developed pre-apical foveae, but these characters might be also plesiomorphies. Setose underside of the body, shape of protibia and flattened eyes are possible homoplasies that have little informativness for the phylogeny of Saprininae in general.