Palaeobasanus, Nabozhenko & Kirejtshuk, 2020

Nabozhenko, Maxim V. & Kirejtshuk, Alexander G., 2020, The Oldest Tenebrionidae (Coleoptera) Of The Subfamily Diaperinae And The Tribe Scaphidemini From The Paleocene Of Menat (France), Acta Zoologica Academiae Scientiarum Hungaricae 66 (1), pp. 23-33 : 25-27

Palaeobasanus gen. n.

Family Tenebrionidae Latreille, 1802

Subfamily Diaperinae Latreille, 1802

Tribe Scaphidemini Reitter, 1922

Type species: Palaeobasanus neli sp. n.

Etymology. The name of the new genus is formed from the Greek “palaeo” (παλαιός – old, ancient) and generic name “ Basanus ”. Gender masculine.

Description. Body oval and medium-sized (body length nearly 7.5 mm). Mouth parts of tenebrioid type, with open basal parts (cardo and stipes); mentum transverse, trapezoidal; gula with rounded margins, not reaching submentum. Antennomeres 5–7 elongate; apical antennomeres (beginning from antennomere 8) forming an unclear club. Pronotum trapezoidal, widest at base; anterior margin twice narrower than base; each side of pronotum with deep furrow along edge. Prosternum moderate before coxae, about twice as long as postcoxal bridge, with cleft lateral margin of the procoxal cavities. Prosternal process narrow between coxae and strongly widened behind coxae. Mesocoxal cavities partly closed by mesepimera and mesotrochantin. Elytra with eight visible distinct striae, each with one row of dense and distinct punctures (elytra with indistinct lateral striae in extant scaphidemins) and scutellary striola; interstriae convex; epipleura narrow, terminating before apex. Abdomen with distinct intersegmental membranes between ventrites 3–5; abdominal intercoxal process widely rounded. Legs (at least hind ones) moderately long, with tibiae subequal in length with femora. Metatarsomere 1 long, but slightly shorter than metatarsomere 4.

Comparison. Palaeobasanus gen n. clearly belongs to the tribe Scaphidemini due to the following characters: tarsi heteromerous; base of scape concealed by gena; tenebrioid mouthparts (open cardo and stipes); cleft lateral margin of procoxal cavities; present scutellary striola; mesocoxal cavities partly closed by mesepimeron and trochantine; tenebrionoid hinging of abdomen with visible intersegmental membranes (defensive glands present).

The new genus is externally similar to extant species of the genus Basanus Lacordaire, 1859 but clearly differs from all Scaphidemini in the structure of the abdominal intercoxal process, which is widely rounded unlike widely truncate. The genus additionally differs from

– Scaphidema Redtenbacher, 1848 and Spiloscapha Bates, 1873 in the antennomeres 4–7 not elongate (gradually or abruptly widening distally) and the large body (in extant genera, the body length is within 3.5–5 mm)

– Basanus Lacordaire, 1859 in the narrower antennomeres and the metatarsomere 1 slightly shorter than metatarsomere 4 (in Basanus , the metatarsomere 1 is clearly longer than metatarsomere 4).

– Laoscapha Schawaller, 2016 in the antennomeres 4–7 not elongate and the metatarsomere 1 clearly longer than metatarsomere 2.