Ligaschonus succiniripae, Alekseev & Pankowski & Bukejs, 2025

Alekseev, Vitalii, Pankowski, Madeline V. & Bukejs, Andris, 2025, A new bark-gnawing beetle (Coleoptera: Cleroidea: Trogossitidae) from Baltic amber, Zootaxa 5631 (2), pp. 380-386 : 382-385

Ligaschonus succiniripae sp. nov.

( Figs 1–2 )

Type material. Holotype: No. KAM 9137 [ KRAM]; “*Holotype / Ligaschonus / succiniripae / gen. et sp. nov. / Alekseev, Pankowski / et Bukejs des. 2025” [red handwritten label]; adult, sex unknown . A complete beetle is included in a transparent, yellowish, amber piece shaped like a trapezoidal prism with dimensions of 21× 9 mm and a maximum thickness of 7 mm. Organic syninclusions: several small fragments of wood dust, one of which is located above the elytra of the beetle. Amber matrix also contains numerous gas bubbles of different sizes.

Locus typicus. Yantarny village (formerly Palmnicken), Sambian ( Samland ) Peninsula, Kaliningrad Region, western Russia.

Stratum typicum. Baltic amber, most probable from the Eocene amber-bearing layers of Blaue Erde (Blue Earth) within the Prussian Formation; estimated age: late Eocene.

Description. Measurements: body length (from anterior tip of mandibles to elytral apex along midline) 4.98 mm, body maximum width across both elytra (at middle) 1.25 mm; head length 0.75 mm, head width (basally) 0.88 mm, head width (between mid-length of eyes) 0.75 mm; pronotal length 1.1 mm, pronotal maximum width (anteriorly) 1.1 mm, pronotal minimum width (at base) 0.8 mm; elytral length 3.13 mm, elytral width (at humeri) 1.13 mm.

Habitus. Body elongate, 3.9× as long as wide, flattened dorsally and ventrally; body uniformly black or blackbrown (as preserved); integument glabrous, punctate, without visible pubescence, scales, or setae.

Head. Prognathous, slightly narrower than pronotum, weakly convex, punctate. Frons simple, without longitudinal median groove and without horn-like processes, with straight anterior margin. Frontoclypeal suture absent. Punctation of frons round, separated by distance of about 1.0× as long as puncture diameter; punctation of vertex elongate, oval, dense, punctures separated by distance of about 0.5× as long as puncture diameter. Compound eyes moderately sized, finely faceted, complete (not emarginated), situated laterally, round in lateral view, elliptical in dorsal view (ellipse with eccentricity 0.57), without interfacetal setae. Mandibles large, with two apical teeth. Maxillary palpi long, with penultimate palpomere cylindrical, 0.5× as long as terminal palpomere; terminal maxillary palpomere spindle-shaped, 3.0× as long as wide at middle. Antennae inserted under lateral margin of frons; antennal insertions not visible from above. Antennal grooves well-developed. Antennae extending to onequarter of pronotum, 11-segmented, with asymmetrical, loose, 3-segmented antennal club; all three segments of antennal club with sensorial fields at inner side; antennomeres 7–10 with erect long sparse hairs. Scape robust, much larger than pedicel; antennomeres 3–8 subequal in size, weakly conical; antennomeres 9–10 subtriangular; antennomere 11 rounded.

Thorax. Pronotum narrowed at base, not cordate, about as long as maximum wide, with fine lateral carina and distinct basal margination, anteriorly wider than head and posteriorly narrower than combined elytral base. Pronotal anterior edge slightly arcuate; posterior edge arcuate. Pronotal disc evenly convex. Anterior pronotal angles not projected, distinct, obtuse, rounded. Posterior pronotal angles triangular, pointed. Pronotal punctation as in vertex, elongate, oval, dense; punctures separated by distance of about 0.5× as long as puncture diameter. Notosternal suture between prohypomeron and prosternum well discernible. Prosternum in front of coxae about 2.0× as long as length of procoxal cavity, convex, punctate; punctures round, medially sparse and laterally denser. Prosternal process extending behind coxae, subparallel, with widely rounded apex. Procoxal cavities externally closed. Scutellar shield small, rounded, about as long as wide.

Elytra. Elongate, subparallel with maximum width at middle, about 2.5× as long as wide, flattened, without carinae, punctate-striate. Each elytron with at least six regular rows of larger strial punctures at disc and irregular rows of finer punctures in interspaces between striae; lateral elytral punctation irregular. Interspaces between striae weakly convex. Epipleura narrow, reaching abdominal ventrite 1, widest at humeri. Mesoventrite convex, densely punctate, punctures separated by distance of about 0.3× as long as puncture diameter, along middle with longitudinal narrow impunctate stripe. Mesocoxal cavities narrowly separated. Metaventrite convex, rather sparsely punctate; punctures irregular, separated by distance of about 1.0–4.0× as long as puncture diameter. Metathoracic wings present (distal parts are exposed).

Legs. Procoxa transverse; mesocoxa subglobose, projecting; metacoxa strongly transverse. Femora finely punctate; profemora subclavate, with flattened and smooth anterior edge for reception of protibiae; meso- and metafemora slightly widened from base to middle. All tibiae flattened, widened apically, rugosely punctate in dorsal view, with two apical spurs; length ratio of protibial spurs 4:3, longer spur is weakly curved; spurs of meso- and metatibiae straight, equal in shape and length. Protibia with two spines in outer apical angle and two spines along outer edge (in anterior quarter and in middle of the tibial length); mesotibia with two small spines along outer edge; metatibia lacks distinct spines along outer edge. Tarsal formula 5–5–5, but seemingly 4–4–4 because tarsomere 1 is minute and retracted into apex of tibia. Tarsomere 5 longest, in all legs as long as all previous tarsomeres together, bearing small bisetose empodium between tarsal claws. Claws simple (without denticles), acute, curved, long (about 0.3× as long as tarsomere 5).

Abdomen. With five ventrites; finely punctate, punctures separated by distance of about 1.0–3.0× as long as puncture diameter. Relative length ratios of ventrites 1–5 equal to 7:7:6:5:5 (measured medially).

Differential diagnosis. As stated above, for the new genus.

Derivatio nominis. The specific epithet succiniripae , used as a noun in the genitive case, is a compound word derived from the Latin ripa succini (amber coast) and meaning “of the amber coast.” The name refers to the poetic name of the southeastern Baltic seacoast.

Remarks. Mesocoxal cavities state (open/close) is not visible in examined specimen due to position of its legs (open mesocoxal cavities are characteristic for Trogossitini ).

Figures

FIGURE 1. Ligaschonus succiniripae gen. et sp. nov., holotype, No. KAM 9137 [KRAM], habitus in dorsal view. A, schematic drawing. B, microphotograph. Scale bars = 1 mm. Abbreviations: apa—anterior pronotal angles; mt—mandibular teeth; ppa— posterior pronotal angles; ss—scutellar shield; ts—tibial spines along outer edge.

FIGURE 2. Ligaschonus succiniripae gen. et sp. nov., holotype, No. KAM 9137 [KRAM]. A, habitus, ventral view. B, habitus, right lateral view. Scale bars = 1 mm.