Archelamprosomius balticus, Bukejs, Andris & Nadein, Konstantin, 2015

Bukejs, Andris & Nadein, Konstantin, 2015, First fossil Lamprosomatinae leaf beetles (Coleoptera: Chrysomelidae) with descriptions of new genera and species from Baltic amber, Zootaxa 3931 (1), pp. 127-139 : 132-135

Archelamprosomius balticus sp. nov.

( Figs 6–10 ; 19)

Types. Holotype: “Nr. 032” [white printed label], “ Holotype / Archelamprosomius balticus sp. nov. / Bukejs & Nadein des.” [red printed label]; sex unknown. A complete beetle with partly exposed hindwings covering the abdominal ventrite 5; ventral side of the specimen partly weakly obscured by a “milky” opacity. The specimen is embedded in a small, elongate amber piece (length about 31 mm, width 12 mm) containing some cracks along the beetle body. Other animals or plant syninclusions are absent in the studied amber piece.

Type strata. Baltic Amber, Upper Eocene, Prussian Formation.

Type locality. Baltic Sea coast, Yantarny village [formerly Palmnicken], Kaliningrad Region, Russia.

Etymology. The epithet of this new species is formed from the locality of its origin.

Description. Body length ca. 3.0 mm, maximum width ca. 2.0 mm; broadly oval, strongly convex dorsally, weakly convex ventrally (abdomen flat); unicolorous black, shiny; glabrous.

Head barely visible from above, deeply retracted into prothorax; with fine, smooth punctuation, shiny; weakly convex in lateral view; vertex without longitudinal medial groove. Eyes entire, not notched, large (vertical diameter somewhat smaller than length of lateral margin of pronotum), convex, with large, distinct facets; vertical diameter 2.2 times as great as transverse diameter. Distance between eyes nearly equal to the vertical diameter of one eye. Antennae slightly visible (due to opacity of amber), 11-segmented, filiform; moderately short, extending beyond base of elytra. Scape large and thick, about 2.1 times as long as pedicel; pedicel subcylindrical; anntenomere 8 approximately 0.7 times as long as antennomere 9; antennomeres 9–11 subequal in length; antennomere 11 with pointed apex. Antennal insertions separated by about 5 diameters of antennal socket.

Pronotum transverse, widest at base; lateral margins nearly straight in lateral view, anterior margin arcuate in frontal view, basal margin weakly sinuate; all margins with carinate borders; anterior angles rounded, bent ventrally and not visible from above, posterior angles almost straight. Pronotal punctation fine, dense, subuniform; distance between punctures 1–3 puncture diameter. Prohypomera shagreened. Intercoxal prosternal process large, lateral sides emarginated, anterior margin straight. Procoxal cavity open posteriorly.

Scutellum minute, triangular. Humeral calli well developed. Elytral punctures small (larger than pronotal punctures) and dense, arranged in 11 regular rows on each elytron, basal punctures larger and deeper than apical punctures; rows distinct along entire length of elytra, but in apical part punctures slightly confused; distance between punctures in rows 0.5–2.0 puncture diameters; intervals flat, with fine and shallow punctures, distinct and dense in the basal half; distance between rows 4–5 puncture diameters. Epipleura horizontal (not visible in lateral view), narrow (anteriorly wider and gradually narrowing posteriorly towards elytral apex), with strongly produced and convex projection in basal 1/3. Macropterous.

Metepisternum shagreened and with fine, dense punctures. Metaventrite depressed in posterior-lateral part, but in the middle and anterior part weakly convex. Disc of metaventrite strongly and densely punctured, distance between punctures 1–2 puncture diameters; shining. Metacoxae transverse, elongate, narrow, distinctly narrower than maximum width of metafemora; shagreened.

Abdomen with ventrite 1 longest, about as long as ventrites 2–4 combined; ventrites 2–4 subequal in length; ventrite 5 approximately 2.5 times as long as preceding ventrite, lateral borders of ventrites with very fine transverse folding; anterior and posterior margins of all ventrites (except widely rounded apex of ventrite 5) almost straight in the middle and distinctly curved towards the apex laterally. Surface shagreened, with fine, sparse punctures (apical half of ventrite 5 covered with denser punctures) and fine, pale, short recumbent setae (especially distinct at posterior margin of ventrite 5). Ventrite 1 proximally with two wide suboval impressions for metafemora reception. Pygidium completely covered by elytra.

Legs relatively short and robust; femora and tibiae with fine punctures and shagreened. Femora and tibiae subequal in length; femora robust, swollen in the middle. Tibiae flattened, slightly widened apically, dorsal surface without groove and with short fine pale recumbent setae, apically with distinctly longer semi-erect dark setae, dorsal surface of protibia convex. Metafemora extending to abdominal ventrite 2. Tarsomeres 1–3 of all legs distinctly dilated; tarsomere 3 deeply bilobed; tarsomere 4 weakly projecting between lobes of tarsomere 3. Tarsal claws relatively large, simple and free (distinctly visible claws on left mesotarsus only).

Comparison. This new species differs from Archelamprosomius kirejtshuki sp. nov. in its shorter legs, tibiae more widened apically, finer elytral punctures, punctation represented by two types of punctures: larger in longitudinal rows and finer on intervals, puncture rows regular.

Figures

FIGURES 6 – 7. Archelamprosomius balticus sp. nov., holotype: 6 — habitus, lateral view; 7 — habitus, ventral view.

FIGURES 8 – 10. Archelamprosomius balticus sp. nov., holotype: 8 — habitus, ventro-apical view; 9 — details of forebody; 10 — habitus, dorso-lateral view.