Trochoideus koenigsbergicus, Alekseev & Tomaszewska, 2018

Alekseev, Vitalii I. & Tomaszewska, Wioletta, 2018, New handsome fungus beetles (Coleoptera: Coccinelloidea: Anamorphidae, Endomychidae) from European amber of the Upper Eocene, Palaeontologia Electronica (6 A) 21 (1), pp. 1-23 : 14-15

Trochoideus koenigsbergicus sp. nov.

Figure 5.4-5

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Type material. Holotype No. 1506-1 [ CCHH], sex unknown. The beetle inclusion is preserved in a polished piece of transparent amber with a yellowish shade and the amber piece is embedded in polyester resin (total measurements are 20 x 15 x 6 mm). The syninclusions consist of three fagacean stellate hairs, one Symphypleona (Collembola), and one Nematocera (Diptera) that is 1.2 mm in length.

Type strata. Baltic amber. Eocene.

Type locality. Russia, Kaliningrad region, the Sambian (Samland) peninsula, Yantarny settlement (formerly Palmnicken) .

Etymology. The species name is derived from Königsberg (now Kaliningrad, Russia), the German name of the capital of the former East Prussia.

Remarks. The new species from Baltic amber is diagnosed as belonging to genus Trochoideus based on following morphological characters: body weakly elongate; broad head with protuberant eyes; pronotum convex, widest near middle of its length and then narrowed posteriorly, with posterior angles right-angled; and elytra elongate-oval with weak, rounded humeral angles.

Diagnosis. Trochoideus koenigsbergicus differs from all extant and extinct species of Trochoideus in having antennae composed of five antennomeres with antennomeres 2–4 equal in proportions. At 3.1 mm long, it is smaller than most members of Trochoideus . Additionally, it can be distinguished from T. mirabilis Strohecker, 1958 , and T. desjardinsi Guérin-Méneville, 1838 by having pronotum widest in anterior one-third; from T. coeloantennatus Strohecker, 1943 , and T. globulicornis Joly and Bordon, 1996 by presence of distinct parasutural elytral striae; from T. mexicanus Strohecker, 1978 , and T. dalmani Westwood, 1838 by an absence of central longitudinal sulcus and long lateral sulci on pronotum; from T. americanus Buquet, 1840 , T. goudoti Guérin-Méneville, 1857 , and T. peruvianus Kirsch, 1876 by disk of pronotum being rugosely punctate at sides; and from T. dalmani Westwood, 1838 , T. wasmanni Strohecker, 1959 , and T. cruciatus ( Dalman, 1825) by having dark, monochromatic elytra.

Description. Body elongate, convex, uniformly dark brown, with short pubescence all over body and legs. Total body length 3.1 mm, width (at widest point) 1.5 mm.

Head with coarse and dense punctation (interspaces as large as puncture diameter). Eyes large, prominent. Fronto-clypeal suture straight. Clypeus covered with dense, relatively long, semierect hairs; and clypeal shape flat, transverse, with subparallel sides. Antennae short, extending to midlength of pronotum; composed of five antennomeres, claviform. Antennomere length proportions follow formula: 2.0: 1.0: 1.0: 1.0: 5.7. Terminal antennomere rounded, weakly widened apically, 2.8 times as long as wide, with few dispersed, long, erect hairs (additional to background pubescence).

Prothorax transverse, 1.3 times wider than long; pronotal anterior margin concave with raised forward, widely-rounded anterior angles; posterior angles right-angled. Lateral margins of pronotum arcuate from anterior margin to anterior one-third, and slightly converging posteriorly within posterior two-thirds. Posterior margin of pronotum weakly bisinuate. Pronotum convex, bordered laterally, without central longitudinal sulcus; lateral sulci distinct, shallow, triangular, as long as one-quarter of pronotal length, connected by deep transverse basal sulcus. Pronotal disc coarsely and moderately densely punctate medially (interspaces 1.0– 2.0 times puncture diameter), rugosely punctate at sides.

Elytra elongate (1.3 times as long as wide, widest at end of anterior one-third), convex; 2.4 times longer than prothorax. Elytral disc finely, densely punctate, with laterally visible pubescence. Punctures irregular, slightly longitudinally oval, interspaces widths equal to 0.5–2.0 puncture diameters, punctures denser basally and sparser apically. Parasutural striae distict, fine, entire. Elytral apices conjointly rounded. Scutellum visible, transverse (about 2 times wider than long), widely rounded posteriorly.

Legs with tarsal formula 4-4-4. Tarsomeres 1– 3 with comb of long hairs ventrally; tarsomere 1 and 4 longest. Tarsal claws simple, long, almost as long as 0.5 times length of tarsomere 4.

Remarks. The characters of the ventral part of the specimen (distance between pro-, meso-, and metacoxae, coxal cavities, number of ventrites, and structure of protibia) are unfortunately not visible on the specimen because the dense milky cover in the surrounding amber.

Note. The extant Trochoideus species have sexually dimorphic antennal structure. The antennae of males and females can differ in form, proportions and number of antennomeres (e.g., four in males and seven in females). The single studied specimen of new species cannot be sexually determined, but sexual dimorphism in the fossil Trochoideus species is very probable.

Figures

FIGURE 5. Endomychids from Baltic and Bitterfeld ambers. 1-3, Laima andreei gen. et sp. nov. (No. 1222-5 [CCHH], holotype), habitus in lateral (1), dorsal (2), and ventral (3) views. 4-5, Trochoideus koenigsbergicus sp. nov. (No. 1506-1 [CCHH], holotype), habitus in dorsal view (4), and antenna in lateral view (5). 6-7, Trochoideus resinatissimus sp. nov., antenna (6) and maxillary palp (7) in lateral views.