The holotype of the new species is deposited in the Menat Town Museum, Village of Menat, Puy-de-Dôme, France (further MTM). This specimen was studied using a stereomicroscope Olympus SCX9 with an Olympus camera in MNHN, a stereomicroscope Nikon SMZ25, a camera Nikon D800, and also with a Tescan Vega LSU scanning electron microscope in MNHN with the Low Vacuum Secondary Electron TESCAN Detector (LVSTD).

The middle Paleocene Menat fossil site (Menat Basin, Puy-de-Dôme, France) is a volcanic maar containing a paleolake ca. 1 km in diameter (46°06’ N; 2°54’ E), which at present contains sedimentary rocks (spongo-diatomites) with remains of diverse aquatic and terrestrial flora and fauna (Nel, 1989, Nel, 2008 and Piton, 1940; etc.). The composition of the faunal and floral remains makes it possible to conclude that this lake was surrounded by a forest. The palaeoenvironment was warm and humid (Wedmann et al., 2018). Following the pollen, mammalian stratigraphic, and radiometric K/Ar analyses, the age of Menat was estimated at 59 Myr (Kedves and Russel, 1982 and Nel, 2008). However, the new estimate based on macroflora postulated its age within 60–61 Myr (Wappler et al., 2009). Some preliminary results of studies on the beetle fauna from Menat outcrop were published by Nabozhenko and Kirejtshuk, 2014 and Nabozhenko and Kirejtshuk, 2017, Kirejtshuk et al. (2016), Legalov et al. (2017), and Kirejtshuk and Nel (2018).

Family: PASSANDRIDAE Blanchard, 1845

Subfamily: PASSANDRINAE Blanchard, 1845

Passandra Dalman, 1817

Type species: Passandra sexstriata Dalman, 1817, by monotypy

= Hectarthrum Newman, 1838 (type species: Hectarthrum curtipes Newman, 1838, by monotypy)

Notes. The new species should be regarded as a member of the generic complex with 11-segmented antenna, a short tarsomere 1, and the absence of the median groove of the head (Catogenus Westwood, 1830, Passandra, Passandrina Reitter, 1878, Nicolebertia Burckhardt and Ślipiński, 1995). It is preliminarily assigned to the genus Passandra due to the smaller number of grooves on elytra and the probable absence of shoulder ribs (characteristic of Catogenus and Nicolebertia). Besides, the new species has no observable pronotal sublateral lines, present in almost all extant species of Passandra (except Passandra sexstriata Dalman, 1817). Also the Eocene species P. septentrionaria possesses these lines only in the basal one-third of the pronotum. However, the new species is distinct from the latter in the different configuration of the grooves on its head. The admedian grooves of the head of the new species are very weak to unclear and do not reach the occipital groove (as in Passandra sexstriata); while in other congeners they are distinct, more or less deep and reach the occipital groove (in general, the admedian grooves of the head of the new species are reminiscent of those in members of Catogenus and Nicolebertia). The abdominal ventrite 5 (hypopygidium) has no trace of preapical groove or impression observable in other species of the generic complex (Catogenus, Passandra, Passandrina and Nicolebertia) and most other passandrid genera, except for Ancistria Erichson, 1845 (Burckhardt and Ślipiński, 2003). Unfortunately, the presence or absence of the oblique keel of the ultimate antennomere is untestable in the holotype of the new species (the ultimate antennomere of the mentioned four genera with a sharp keel or “indistinctly keeled” in Nicolebertia: Burckhardt and Ślipiński, 2003). Finally, the Passandrinae is characterized by the small labrum inclined ventrally between mandibles and not visible from above. The labrum of the new species is shaped as in other passandrines, but clearly visible in the imprints of the holotype examined. Thus, the new species is most similar to the species of Passandra (defined by Burckhardt and Ślipiński, 2003 and Slipinski, 1987), although it demonstrates the exposed labrum and the absence of preapical groove or impression on its hypopygidum, and it is a reason why its attribution is here considered as preliminary.

(?) Passandra plenaria sp. n.

(Fig. 1, Fig. 2, Fig. 3 and Fig. 4)

Etymology. The species name derives from the Latin “plenarius” (complete, finished).

Type locality and stratum. Menat Basin, Puy-de-Dôme, France. Middle Paleocene (46°06’ N; 2°54’ E), collected in a new, small outcrop near the south-east of the village of Menat.

Holotype: “Nel 3036,” imprint and counterimprint (obliquely cracked through its mid-length), well preserved on rather smooth piece of rock; the specimen shows the main parts of body sclerites in upper and lower views, but some left antennomeres, three tibiae and most tarsomeres are missing.

Description of holotype. Body length 11.8 mm, maximum width 3.6 mm. Body elongate-oval, 3.3 times as long as wide.

Head slightly narrower than pronotum; impunctate. Admedian grooves diverging anteriorly, expressed in anterior third of head length and becoming obliterated posteriorly, sublateral grooves well developed throughout their entire lengths, curved along lateral angles of frons and joined posteriorly to the occipital groove; occipital groove clear, sinuate medially. Median projection of frons moderately narrow, with emarginate anterior margin (Fig. 2A and Fig. 4A). Eyes moderately small, apparently about as long as antennomere 1 (scape) wide, slightly prominent, moderately convex. Antennae long and slender, extending to the basal one-third of the elytra; scape large, subcylindrical, about 1.2× as long as wide; pedicel small, about as long as wide and approximately 0.6 times as long as antennomere 3; antennomeres 3–10 subcylindrical and slightly thickened apically, about twice as long as wide; antennomere 11 elongate-oval, about twice as long as wide.

Pronotum slightly transverse, 1.1 times as wide as long, widest at anterior angles, sides subparallel in anterior two-thirds and distinctly narrowed posteriad. Anterior angles slightly protruding, subrectangular, narrowly rounded; anterior margin slightly bisinuate, with bordering joined to bordering of pronotal sides; pronotal sides with narrow and complete border. Disc impunctate; sublateral lines absent.

Scutellum moderately large, about as long as wide, pentagonal. Elytra about 1.8 times as long as their combined width; base markedly wider than the pronotal posterior margin. Elytra with three complete striae (1, 5, 6); stria 1 grooved throughout entire length and joined at apex to the bordering of the elytral sides; striae 5 and 6 grooved in basal four-fifths of the length; stria 4 distinct in basal fourth of the elytral length, striae 2 and 3 indistinct. Intervals smooth.

Legs short and robust. Femora rather thick. Protibia looking like moderately and metatibia rather wide. Pro- and metatarsi five-segmented. Tarsomere 1 of pro- and metatarsi short, distinctly shorter than tarsomere 2, partly covered by tibial apex; tarsomeres 2–4 short; protarsomere 5 about as long as tarsomeres 3–4 combined. Protarsal claws small.

Abdomen with five ventrites; ventrite 5 without visible groove or impression along the posterior margin.

The extant members of the family Passandridae are distributed mostly in tropical and subtropical territories beyond Europa. Only few species of Passandra, Ancistria, and Aulonosoma Motschulsky, 1858 have been recorded in the southern part of the Palearctic Asia, including South Korea, and Japan (Jin et al., 2019 and Park et al., 2005), while two fossil species of the subfamily Passandrinae sensu str. originated from European outcrops of the Paleogene (Baltic amber: Alekseev et al. (2016) and Menat); however, one species of the subfamily Mesopassandrinae was found in the Albian–Cenomanian (most probably earliest Cenomanian) Burmese amber (Jin et al., 2019). The latter subfamily demonstrates some characters that make it possible to assign it to the family Passandridae as well as to the family Laemophloeidae, and its placement needs to be clarified by new data and arguments. Most diagnostic peculiarities of the Mesozoic subfamily (labrum broad and well exposed dorsally, mandibles narrow, strongly angled externally and bidentate apically, antennae with antennomere 3 distinctly longer than antennomeres 4 or 5, and male tarsal formula 5–5–4) occur in various members of Laemophloeidae. Crowson (1967) argued for the distinctiveness of the family Passandridae mostly by the presence of confluent gular sutures and of contiguous anterior tendons in adults, while all other “clavicornian” families (Cucujoidea sensu lato, including cerylonid-families or Coccinelloidea) have separate gular sutures. Crowson (1967) linked this family with Cucujidae (including Silvaninae, Phlaeostichinae, Laemophloeinae, Prostominae). Burckhardt and Ślipiński (2003) added to the above-mentioned diagnostic characters of Passandridae also the “large mandibles with exposed articulation,” “usually closed mesocoxal cavities” and “strongly inequal tibial spurs”. However, the gular sutures that in Passandridae should be confluent at the base of the head are not observable in Mesopassandra. Moreover, the convergent paramedian longitudinal impressions behind the mentum can be traced in some passandrids and they are reminiscent of gular sutures of other cucujoids. Lawrence and Ślipiński (2013) indicated strongly projecting the genal process (“jugular lobes”) as an important passandrid character. Their presence in Mesopassandra was interpreted by Jin et al. (2019) as a strong hint allowing to place it among passandrids. However, the development of these processes demonstrates a great variability in this family and scarcely can be a reliable indication of a passandrid attribution. Also, the tibial spurs of laemophloeids are unequal and generally much smaller than those of passandrids. Thus, the tibial spurs also are equivocal characters for this family. The same pertains the closed mesocoxal cavities and some other ambiguous structural peculiarities of Mesopassandra (bifid mandibular apices, wide and exposed labrum, narrowly separated meso- and metacoxae, etc.). The sexual dimorphism in tarsal formula can be interpreted as a scarcely plesiomorphic cucujoid character, as was supposed by Jin et al. (2019). As a result, only the “mandibles with exposed articulation” remain an argument to link this genus with passandrids. Therefore, it is reasonable to regard its attribution to Passandridae as rather problematic, needing further arguments thanks to additional fossil material. Besides, the distinctiveness between this family and Laemophloeidae also needs a detailed analysis.