Groehnius electrum, Bukejs & Legalov, 2019

Bukejs, Andris & Legalov, Andrei A., 2019, Groehnius, a new genus of Eugnomini (Coleoptera: Curculionidae) from Eocene Baltic amber, Fossil Record 22 (2), pp. 45-49 : 46-48

Groehnius electrum sp. nov.

urn:lsid:zoobank.org:act:174 CA 693-74E9-48AC-

A014-52A2C20A70BD

Figs. 1–2 .

Etymology

The species name is a noun in apposition and is one of the Latin words for amber – electrum .

Holotype

Holotype: “coll. Gröhn 8607”, deposited at the Center of Natural History (Centrum für Naturkunde – CeNak; formerly the Geological-Paleontological Institute and Museum – Das Geologisch-Paläontologische Museum, GPIH) of the University of Hamburg, Germany; adult, sex unknown. Complete beetle included in transparent yellow piece of amber with dimensions 33 mm × 18 mm × 4 mm. Ventral side of specimen almost completely obscured by “milky cover”. Syninclusions : one undetermined Brachycera (Diptera) specimen, few stellate Fagaceae trichomes, and some gas vesicles.

Type strata

Baltic amber, mid-Eocene to Upper Eocene.

Type locality

Baltic Sea coast, Yantarny settlement (formerly Palmnicken), Kaliningrad region, Russia.

Description

Measurements: body length (without rostrum) 3.5 mm, rostrum length about 1.1 mm; head length 0.3 mm, head width (including eyes) 0.55 mm; pronotum length 0.88 mm, pronotum maximum width 0.95 mm; elytra length 2.4 mm, elytra maximum width 1.45 mm.

Body: elongated, slightly convex; unicolorous black (as preserved). Pubescence: body moderately densely covered with short, fine recumbent setae dorsally and ventrally; pronotum additionally with sparse, longer recumbent setae, with long, erect seta near each angle, and with short curved hair-like scales at lateral sides; elytra additionally with sparse, longer erect setae.

Head: prognathous, apparently without distinct punctation; forehead slightly convex. Rostrum long, about 1.4 times as long as pronotum, moderately curved downward, slightly dilated anteriad; antennal scrobes lateral, slightly obliquely directed toward the rostrum base; rostrum about 5.5 times as long as wide apically, 7.3 times as long as wide medially and basally; apparently with dense, fine punctation. Compound eyes very large, suboval, slightly convex. Temples about 0.3 times as long as transverse diameter of one eye. Antennae with 11 antennomeres, clavate, with distinct three-segmented club; sparsely covered with short, semierect setae; inserted in apical one-third of rostrum; moderately long, reaching nearly basal one-third of pronotum; scape elongate, not reaching anterior margin of eye, distinctly dilated apically, about 2.7 times as long as antennomere 2; funicle (antennomeres 2–8) slender, 2.9 times as long as club; antennomere 2 elongate, subcylindrical, as wide as scape apically and about 3 times as wide as antennomere 3; antennomeres 3–4 elongate, cylindrical, subequal in length and wide; antennomeres 5–6 slightly elongate, 2.0–1.5 times as long as wide; antennomeres 7–8 quadratic, about as long as wide; antennal club rather wide and long, 1.9 times as long as wide, antennomeres 8–9 transverse, 1.2–1.4 times as wide as long, antennomere 8 about 2.3 times as wide as antennomere 7, antennomere 11 tapered apically.

Pronotum: slightly transverse, about 1.2 times as wide as long, distinctly narrower than anterior elytral margin, with

A. Bukejs and A. A. Legalov: Groehnius , a new genus of Eugnomini 47

constriction at anterior margin, widest medially, distinctly narrowed anteriad and slightly narrowed posteriad; disc slightly convex; densely covered with large and deep punctation, distance between punctures distinctly smaller than diameter of one puncture. Lateral margins widely rounded in basal three-fourths and straight in anterior one-fourth; anterior margin almost straight; posterior margin slightly rounded. Precoxal portion of prothorax elongate, postcoxal portion short.

Elytra: elongate, 1.7 times as long as wide, about 3.0 times as long as pronotum, with almost parallel lateral sides in anterior two-thirds and gradually narrowing in posterior one-third. Elytral punctation apparently dense and large, punctures arranged in regular striae; intervals distinctly convex, wider than striae. Humeri developed, prominent.

Abdomen: with five visible ventrites, slightly convex; ventrites 3 and 4 short, equal in length, ventral plate 3 distinctly narrower than ventral plate 2, ventral plate 4 about 0.7 times as long as ventral plate 5. Relative length ratios of ventrites 1–5 equal to 15–15–7–7–10.

Legs: long, slender, covered with sparse, recumbent setae and fine punctures; femora and tibia subequal in length. Femora spindle-shaped, slightly swollen medially, without teeth ventrally. Tibiae elongate, without mucro or uncus, almost straight, protibia about 9.1 times as long as wide medially. Tarsi elongate, about 0.5 times as long as tibia, tarsomere 1 elongate, slightly dilated apically, tarsomere

48 A. Bukejs and A. A. Legalov: Groehnius , a new genus of Eugnomini

2 shorter than tarsomere 1, distinctly dilated apically, tarsomere 3 bilobed, strongly dilated apically, tarsomere 5 narrow; metatarsomere 1 about 3.4 times as long as wide, metatarsomere 2 about 1.3 times as long as wide, 0.5 times as long as metatarsomere 1. Claws free, simple (without teeth basally), branched.

Figures

Figure 1. Groehnius electrum gen. et sp. nov., holotype: (a) habitus, dorsal view; (b) habitus, ventrolateral view. Scale bar = 1 mm.

Figure 2. Groehnius electrum gen. et sp. nov., holotype: (a) details of fore-body, dorsal view; (b) details of fore-body, ventrolateral view. Scale bar = 0.5 mm.