Carstenium kensbargense, Alekseev & Bukejs, 2024

Alekseev, Vitalii & Bukejs, Andris, 2024, A new extinct genus of the tribe Hedobiini (Coleoptera: Ptinidae) from Baltic amber, Baltic Journal of Coleopterology 24 (2), pp. 223-230 : 225-228

Carstenium kensbargense sp. nov.

( Figs 1–2 )

Type material. Holotype: No. GPIH no. 5231, CCGG no. 8711 (ex coll. Jonas Damzen JDC-13523); “ Holotype / Carstenium kensbargense gen. et sp. nov. / Alekseev V. et Bukejs A. des. 2024” [red printed label]; adult, sex unknown. A rather complete beetle (right elytron damaged and legs partially cutted off during amber piece preparation) with partially exposed metathoracic wings is included in a transparent, yellow amber piece with dimensions of 26× 13 mm and a maximum thickness of 3 mm, preserved without supplementary fixation. Syninclusion: one specimen of Nematocera (Diptera).

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Alekseev V., Bukejs A.

Type stratum. Baltic amber from Eocene amber-bearing Blaue Erde deposits; estimated age: middle–late Eocene ( Standke 1998; Sadowski et al. 2017, 2020; Seyfullah et al. 2018; Bukejs et al. 2019).

Type locality. Yantarny settlement (formerly Palmnicken), Sambian (Samland) Peninsula, Kaliningrad Region, Russia .

Description. Measurements: body length (from anterior margin of head to elytral apex along midline) 5.1 mm, body maximum width across both elytra 2.15 mm; pronotum

226 length 1.2 mm, pronotum maximum width 1.5 mm, pronotum width at base 1.4 mm; elytra length 3.8 mm, elytra maximum width about 2.15 mm.

Body shape elongate oval, subcylindrical, subflattened dorsally and slightly convex ventrally; body color dark brown, with pronotum, prothorax and head black (as preserved). Pubescence: dorsum sparsely covered with fine, erect setae; ventral surface of thorax and abdominal ventrites with shorter, semierect setae; legs with denser, fine pubescence.

Head partially retracted into prothorax, densely covered with fine punctation; vertex flat; frons weakly convex. Compound eyes rather small, widely oval, strongly convex, entire, finely facetted, without ommatidial setae; distance between compound eyes wide, equal to 2.15× vertical diameter of one eye. Mandibles short, robust. Maxillary palpi with four palpomeres; palpomeres 2 and 3 elongate, assimetrical, dilated apically; palpomere 4 nearly securiform, strongly dilated. Antennal insertions distant from inner margin of eyes; narrowly separated by distance of 0.75× vertical diameter of one eye. Antennae with 11 antennomeres, filiform (antennomeres not flattened), rather short, extending about to anterior one-fifth of elytra length. Scape subcylindrical, elongate, 2.15× as long as wide; pedicel conical, slightly elongate, 1.25× as long as wide, narrower and shorter, about 0.4× as long as scape; antennomere 3 shortest, subtrapezoidal, as long as wide, slightly shorter than pedicel; antennomere 4 conical, slightly dilated apically, strongly elongate, 2.0× as long as wide; antennomeres 5–10 subequal in size and shape, subconical, dilated apically, elongate, 2.2× as long as wide; antennomere 11 spindle-shaped, pointed apically, elongate, 2.5× as long as wide. Relative length ratios of antennomeres 1–11 equal to 13:5:4:?10:10:10:10:10:10:10:10

Pronotum subquadrate, distinctly narrower than elytral base, weakly transverse, 1.25× as wide as long, with maximum width at middle, lateral sides slightly narrowed anteriad and posteriad; disc almost flat, convex anterolaterally and slightly impressed at anterior margin, without carinae. Pronotum laterally rounded, pronotal lateral edge absent. Pronotal punctation small and rather dense, distance between punctures about equal to 1.0–1.5× diameter of one puncture; interspaces with dense micropunctation. Posterior pronotal angles distinct, rectangular, sharp; anterior

227 angles rounded. Anterior pronotal margin rounded and convex medially; posterior margin weakly bisinuate, bordered; lateral sides weakly rounded. Prosternum convex, covered with fine punctation. Prosternal process wide, about 0.8× as wide as transverse diameter of procoxa, dilated apically, with straight apical margin.

Scutellar shield subpentagonal, with slightly rounded apex, transverse, 1.3× as wide as long, densely covered with small punctation.

Elytra subparallel with maximum width in posterior one-third, elongate, about 1.8× as long as wide, weakly convex to flat; basal margin bisinuate; humeri well-developed. Elytral punctation dense, rather large (larger than pronotal punctures), partially arranged in subregular striae, striae more or less distinct on disc, distance between punctures about equal to 1.0–1.5× diameter of one puncture; interspaces apparently weakly convex, covered with micropunctation. Epipleura wide near humeri and gradually narrowing postriad reaching elytral apex, punctate. Metaventrite with disc convex, covered with rather dense, fine punctation. Metanepisternum rather narrow, about 5.1× as long as wide, covered with fine punctation. Metathoracic wings developed.

Legs slender, long. Procoxae subconical, projecting, widely separated by 0.8× transverse diameter of procoxa; mesocoxae nearly globose, narrowly separated by about 0.3× transverse diameter of mesocoxa; metacoxae strongly transverse, 4.0× as wide as long, narrowly separated by 0.7× length of metacoxa. Mesotrochanters subtriangular, rather small; metatrochanters enlarged, drop-shaped, rounded apically. Femora slender, narrowly oval, non-clavate, 5.0× as long as wide, weakly and gradually dilated apically; femora and tibiae subequal in length. Tibiae straight, not dilated apically; with at least one large, curved, sharp apical spur in mesotibia; with two short, right,

228 sharp and equal in size spurs in metatibia. Tarsi (meso- and metatarsus partially preserved only) long, mesotarsus about 0.8× as long as mesotibia length; tarsomere 1 cylindrical, elongate, 3.1× as long as wide, about as long as tarsomeres 2 and 3 combined; tarsomere 2 subconical, elongate, 1.3× as long as wide; tarsomere 3 triangular, strongly dilated apically, as long as wide; tarsomere 4 widened apically, deeply bilobed; tarsomere 5 long, suncylindrical, slightly curved, about 1.3× as long as tarsomere 4. Tarsal claws simple, about 0.5× as long as tarsomere 5; swollen basally, without tooth.

Abdomen with five visible ventrites, covered with fine punctation; ventrite 1 with small, triangular intercoxal process; ventrite 5 rounded apically. Relative length ratios of ventrites 1–5 equal to 7:11:11:11:16 (measured medially).

Derivatio nominis. The species name “kensbargense ” is toponymic and derived from “Kensbarg”, i.e. Königsberg (the historical capital of East Prussia) in the Low Prussian dialect of Low German language.

Figures

Fig. 1. Carstenium kensbargense gen. et sp. nov., holotype, No GPIH no. 5231: A – habitus, dorsal view; B – habitus, ventral view.

Fig. 2. Carstenium kensbargense gen. et sp. nov., holotype, No GPIH no. 5231: A – details of forebody, dorsal view; B – head and prothorax, ventral view. Abbreviations: pc – procoxa; pp – prosternal process.