Podosilis groehni, Bukejs & Fanti, 2023

Bukejs, Andris & Fanti, Fabrizio, 2023, Two new fossil Silinae (Coleoptera, Cantharidae) from Baltic amber, Baltic Journal of Coleopterology 23 (2), pp. 331-339 : 332-334

Podosilis groehni sp. nov.

( Fig. 1 )

Type material. Holotype: GPIH no. 5202, CCGG no. 8701 (ex coll. Jonas Damzen JDC-12438); adult, male. A complete beetle with partially exposed metathoracic wings is included in a transparent, yellow amber piece with dimensions of 36× 19 mm and a maximum thickness of 6 mm; preserved without supplementary fixation. Syninclusions: one Brachycera (Diptera) specimen, two Nematocera (Diptera) specimen, seven? Acarina (Arachnida) nymphs, and few stellate Fagaceae trichomes.

Type locality. Amber mine in Yantarny settlement, the Sambian Peninsula, the Kaliningrad Region, Russia .

Type stratum. Baltic amber; Middle– Upper Eocene ( Sadowski et al. 2017, 2020; Seyfullah et al. 2018; Bukejs et al. 2019; Kasiński et al. 2020).

Systematic placement. The specimen considered here was assigned to the genus Podosilis based on a combination of the following morphological characters: (1) internal claws of all legs apically bifurcate (simple in Eusilis , Silis and Autosilis , and only the internal claw of forelegs apically bifurcate in Asiosilis ), (2) claws without denticle basally (all claws with large denticle in Asiosilis ), and (3) tarsomere 4 is widest than others tarsomeres (narrow as others tarsomeres in Eusilis ).

Differential diagnosis. Podosilis groehni sp. nov. differs from P. gedaniensis Kazantsev, 2020 (the single fossil species of the genus, the holotype is female) by the obsolete elytral humeral costae (distinct in P. gedaniensis ); this character cannot be considered as sexual dimorphism. Also, the new species differs from the extant species of Podosilis in having a extremely smaller body size.

Two new fossil Silinae ( Coleoptera , Cantharidae ) from Baltic amber

Description. Body elongate-oval, slightly flatened dorsally; sparsely covered with homogenous, short, semierect setae; integument unicolorous brown (as preserved). Measurements: total body length 3.0 mm (from anterior margin of head to elytral apex); pronotum length 0.5 mm, pronotum maximum width 0.8 mm; elytra length 2.4 mm, elytra maximum width 1.2 mm, elytra width at base 1.0 mm.

Head short, transverse, pubescent, with fine punctation, partially covered by pronotum; frons convex. Compound eyes large, hemispherical and strongly prominent, inserted laterally. Mandibles large, simple, and falciform. Maxillary palpi 4-segmented, palpomeres unequal in length, terminal palpomere weakly securiform. Labial palps 3-segmented, terminal palpomere securiform. Antennae inserted far from inner margin of eyes, rather long, extending about to posterior one-third of elytral length; 11-segmented, filiform, all antennomeres covered with short, semierect setae; scape subcylindrical, dilated apically, elongate, 2.5× longer than wide, robust, curved; antennomere 2 shortest, subtrapezoidal, dilated apically, slightly elongate, 1.25× longer than wide, about 0.5× as long as scape; antennomere 3 subcylindrical, slightly dilated apically, elongate, 2.25× longer than wide, slightly shorter than antennomere 4; antennomeres 4–8 equal in size and shape, robust, subcylindrical, dilated apically, elongate, 2.5× longer than wide, about 2.0× as long as antennomere 2; antennomeres 9–10 equal equal in size and shape, robust, subcylindrical, dilated apically, slightly shorter than antennomere 8; antennomere 11 elongate-oval, 3.1× longer than wide, narrowly rounded at apex;

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relative length ratios of antennomeres 1–1 equal to 10:5:9:10:10:10:10:10:9:9:11.

Pronotum subtrapezoidal, transverse, 1.6× wider than long, widest in posterior one-third of its length, slightly wider than head; punctation fine and sparse on disc, and distinctly denser laterally; disc convex, with subtriangular impressions basally and suboval impressions anterolaterally. Pronotal apical margin slightly rounded; basal margin almost straight; lateral margins rounded, incised near base and near anterior angles, protruding posteromedially with two small and obtuse tooth. Anterior angles obtuse, slightly projecting; posterior angles acute, distinctly projecting posteriad forming denticle. Prohypomera densely covered with fine punctation.

Scutellar shield subtriangular with widely rounded apex, with few fine punctutes. Elytra wider than pronotum, elongate-oval, 2.0× longer than wide, subparallel-sided in anterior half and slightly widened in posterior half, rounded apically, completely covering abdomen; humeral costae obsolete, slightly distinct in anterior two-thirds of elytral lenght; with large oval impression post-medially; elytral punctation small and rather dense, distance between punctures about 0.7–1.3× diameter of one puncture, punctures distinctly denser laterally. Metanepisternum subtriangular, narrowed posteriad, with fine punctation.

Metaventrite wide, with rounded posterior margin, covered with fine punctation; disc convex, apparently with discrimen.

Metathoracic wings fully developed.

Legs rather long, slender, pubescent. Procoxae conical, large; mesocoxae narrowly oval, convex; metacoxae narrow, strongly transverse. Trochanters elongate, convex. Femora narrow, slightly flattened, straight. Tibiae subcylindrical, apparently with two spines apically, pro- and mesotibiae nearly as long as pro- and

334 mesofemora respectively, metatibiae distinctly longer than metafemora. Tarsal formula 5-5-5; tarsomere 1 longest, elongate, slightly dilated apically; tarsomere 2 shorter than tarsomere 1; tarsomere 3 subtriangular, dilated apically, shorter than tarsomere 2; tarsomere 4 widest, deeply bilobed; tarsomere 5 subcylindrical, elongate, curved, enlarged apically. Pretarsal claws without basal tooth, inner claw of all legs bifurcate apically.

Abdomen with seven visible sternites (ventrites), covered fine, inconspicuous punctation; sternite 7 with elongate lobe with rounded apex; ultimate tergite longer and wider than ultimate sternite, with prominent conical lateral processes.

Etymology. The specific epithet is a patronym; the new species is named in honor of Mr. Carsten Gröhn (Glinde, Germany), an enthusiast and specialist in Baltic amber.

Remark. The lateral margins of pronotum incised and denticulated, and the ultimate abdominal sternite long and narrow indicate that the specimen is male.

Figures

Fig. 1.Podosilis groehni sp. nov., holotype, No 5202 [GPIH]: A – habitus, dorsal view; B – habitus, ventral view.