Heterlimnius samlandicus ( Bollow, 1940 ) Bollow, 1940

Bukejs, Andris, Alekseev, Vitalii I. & Jäch, Manfred A., 2015, The riffle beetles (Coleoptera: Elmidae) of the Eocene Baltic amber: Heterelmis groehni sp. nov. and Heterlimnius samlandicus (Bollow, 1940) comb. nov., Zootaxa 3986 (4), pp. 452-460 : 453-454

Heterlimnius samlandicus ( Bollow, 1940) comb. nov.

( Figs 1–4 )

Material examined. Holotype Nr. 4396 ( GPIH), sex unknown. The holotype is complete. Bollow (1940) noted, that the right middle leg was absent, but in fact it is present, the tibia and tarsus just being tucked. The specimen is embedded in a flat orange amber piece (maximal length 40 mm, maximal depth 7 mm). There are 46 animal syninclusions: Arachnida (a few mites, one spider); Collembola; Hemiptera (one aphid); Diptera (numerous specimens); Trichoptera ( Electrohelicopsyche taeniata Ulmer, 1912 ), Coleoptera (one Scydmaeninae ). Numerous fagacean trichomes are also present. Photographs of the studied amber piece and attendant labels are shown in Fig. 3 .

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

Type locality. Palmnicken [now Yantarny settlement], Sambian [Samland] Peninsula, Kaliningrad Region, Russia.

Re-description. Body length 3.25 mm, maximum width 1.65 mm; subovate, convex dorsally and ventrally; unicolorous blackish bronze, shiny, sparsely covered with moderately short, black recumbent setae; pronotal setae directed to center of disc, elytral setae directed posteriad and arranged in rows.

Head prognathous, together with eyes narrower than pronotum. Eyes moderately large (subequal in size to procoxa), convex, with distinct facets. Clypeus with very fine distinct punctures, with widely rounded anterior margin. Labrum transverse, with widely rounded anterior margin; apparently with fine punctures. Maxillary palpomere 4 elongate, subcylindrical, three times as long as wide, with rounded apex. Apices of labial palpi truncate. Antennae filiform, long, extending to base of pronotum; 11-segmented, scape and pedicel widest, subcylindrical; antennomeres 3–10 thin, weakly dilated apically, subequal in length and shape; antennomere 11 symmetrical, about 1.4 times as long as antennomere 10, with pointed apex; relative length ratios of antennomeres 1–11 equal to 5:7:6:5:5:5:5:5:5:5:7.

Pronotum subtrapezoidal, transverse (1.4 times as wide as long), widest in posterior third; disc convex, lateral sides rather sloping; lateral margins of pronotum almost straight and gradually divergent from anterior margin to posterior third, then weakly concave to posterior angles. One pair of pronotal sublateral longitudinal grooves present, very narrow, weakly curved, extending from base to about basal 3/5. Basal transverse depression very shallow. Lateral margins of pronotum distinctly bordered (wider anteriorly), non-crenulate; posterior pronotal margin slightly bisinuate, anterior margin convex; posterior angles acute, anterior angles slightly produced. Pronotal punctation fine and moderately sparse at disc (distance between punctures 1–1.5 × one puncture diameter), denser toward anterior margin and coarser toward posterior angles.

Scutellum moderately large, roundly pentagonal, pointed apically; about 1.2 times as long as wide, flat, shiny, without punctation. Elytra 1.49 times as long as wide, at base wider than pronotum; widest before middle; convex on disk and weakly sloping at sides; acuminately separately rounded at apex; lateral borders non-crenulate. Lateral sides gradually convex in basal 3/4, strongly narrowed in apical 1/3. All intervals uniform, slightly convex, not carinate. Anterior part of third interval subequal in width to 4th interval, fused at about apical third. Punctures fine (almost equal in size to pronotal ones) and densely arranged in almost regular longitudinal rows; distance between rows 3–4 × as wide as a puncture diameter; distance between punctures in striae equal to 1–2 × one puncture diameter. Intervals between rows with additional, sometimes irregular punctation and 1–2 rows of recumbent setae. Hind wings obviously present, because of well-developed humeri.

Prosternum and metaventrite with coarse and dense punctation (distance between punctures shorter than a puncture diameter). Prosternum produced anteriorly. Intercoxal prosternal process semicircular, nearly as long as wide at base; at apex wider than transverse diameter of procoxa; slightly impressed in apical half. Procoxae globose, distance between procoxae nearly equal to 1.25 transverse diameter of procoxa. Trochantins not exposed. Mesocoxae nearly globose, distance between mesocoxae nearly equal to 1.25 transverse diameter of mesocoxa. Metacoxae roundly triangular, slightly transverse; distance between metacoxae nearly equal to 0.7 transverse diameter of metacoxa. Epipleura narrow, reaching ventrite 2.

Abdomen with five ventrites. Relative length ratios of ventrites 1–5 equal to 25:15:15:12:27. Ventrite 1 distinctly longer than ventrite 2, anterior margin between metacoxae produced, widely rounded, coarsely and densely punctate. Ventrites 2–3 equal in length, posterior margins concave. Ventrites 2–5 densely punctate medially. Apex of ventrite 5 slightly emarginate.

Legs relatively long and slender. Trochanters elongate. Femora weakly widened medially, subflattened. Tibiae almost straight, almost equal in length to femora; with thin setae. Tarsi long and thin, tarsal formula 5–5–5; tarsomeres subcylindrical, tarsomeres 1–4 with brush of setae ventrally; tarsomere 5 as long as tarsomeres 1–4 combined. Claws curved, simple, long (nearly half as long as tarsomere 5).

Figures

FIGURES 1 – 4. Heterlimnius samlandicus, holotype, 4396: 1 — habitus, dorsal view; 2 — habitus, ventral view; 3 — general view of amber piece with labeling; 4 — tibia and tarsus of hind leg, dorsal view.