Genus Palaeocnopus gen. nov. Alekseev & Grzymala

Type species: Palaeocnopus densipunctatus sp. nov. Alekseev & Grzymala, here designated

Diagnosis. The combination of small overall body size (1.4–1.8 mm), the deep basal pronotal impressions, the elytra with uniseriate pubescence, the coarsely faceted and protuberant eyes, and the metathoracic femora without any excavation or modified setal comb or brush differs from all currently described extant and extinct genera of Aderidae. This new genus most closely resembles Cnopus Champion, 1893, but can be distinguished by the two deep, lateral triangular impressions at the anterior pronotal angles and the metathoracic legs with metatarsomere I equal to or slightly longer than the following metatarsomeres combined.

Description. Body small and elongate (1.4–1.8 mm), upper surface clothed with uniseriate pubescence, with one seta arising anterad of each puncture, without additional setae between; antenna long, filiform, 11-segmented; eyes large, oval, hemispherical, coarsely faceted, adjacent to hind margin of head; pronotum transverse, maximal width at or close behind middle, with two deep, lateral triangular impressions at anterior angles and 1–2 shallow to deep basal or sub-basal impressions, form of which is species-specific; separation of abdominal ventrite I and abdominal ventrite II visible laterally, obsolete medially; metafemur simple, lacking distinctive comb or brush of modified setae, metatarsomere II bilobed and metatarsomere III small.

Etymology. The new genus-group name Palaeocnopus is composed of “ palaeo ” (meaning old, ancient) and “ Cnopus ”, the name of its putative sister genus. The name is masculine.

Species composition. Four newly described extinct species.

Remarks. Several observed characters, such as the antennomere ratios and the size of the eyes and area between them, are assumed to be sexually dimorphic because all other characters appear to be constant between specimens. These differences have been observed between males and females of extant aderid taxa, such as those in the genus Euglenes Westwood, wherein males have elongate antennomeres and enlarged eyes as compared to females. These characters can later be confirmed by finding a pair of Palaeocnopus “ in copula ” within an amber inclusion.

Systematic placement. The genus Palaeocnopus shares several putative morphological synapomorphies with the potentially closely related genus Cnopus Champion, 1893 such as the globular pedicel, the coarsely faceted eyes lacking anterior emargination, the deep basal pronotal impressions, the uniseriate elytral pubescence, and the absence of any metathoracic femoral modifications. Preliminary phylogenetic analyses of the Aderidae place this genus within a clade containing the genera Cnopus, Scraptogetus Broun, 1893, and the currently unplaced North American species ‘ Xylophilus ’ constrictus Fall, 1901, based upon the globular pedicel, the coarsely faceted eyes lacking anterior emarginations, the shallow to deep pronotal impressions, and uniseriate elytral pubescence. The higher-level classification of the Aderidae is currently under revision (TLG in preparation) and we refrain from discussing the phylogenetic placement of this new genus further in order to avoid future classification confusion.