Metaclisa (Trichometaclisa) ottoi, Nabozhenko & Mckellar & Bukejs, 2021

Nabozhenko, Maxim V., Mckellar, Ryan C. & Bukejs, Andris, 2021, The first described darkling beetle of the tribe Metaclisini (Coleoptera: Tenebrionidae) from Eocene Baltic amber, Zootaxa 4999 (3), pp. 279-284 : 280-283

Metaclisa (Trichometaclisa) ottoi sp. nov.

( Figs. 1–2 )

Material. Holotype: collection number P3300.143 [ RSKM]; adult, sex unknown. The complete beetle with partially exposed metathoracic wings is included in a transparent, yellow amber piece with approximate dimensions of 51 mm × 15 mm and a maximum thickness of 8 mm; preserved without supplementary fixation. Organic syninclusions: tarsus of unknown insect, and some stellate fagacean trichomes.

Type stratum. Mid-late Eocene, 48–34 Ma ( Sadowski et al. 2017, 2020; Seyfullah et al. 2018; Bukejs et al. 2019; Kasiński et al. 2020).

Type locality. Baltic Sea coast, Yantarny settlement (formerly Palmnicken), Sambian (Samland) Peninsula, Kaliningrad Region, Russia .

Description. Measurements: body length 10.9 mm; head length 0.9 mm, head width (across compound eyes) 1.9 mm; pronotum length 2.3 mm, pronotal maximum width 4.5 mm; elytral length 7.6 mm, elytral maximum combined width 4.2 mm.

Body elongate-oval, nearly parallel-sided, slightly convex; unicolorous, dark brown (as preserved), shining. Pubescence: elytra and apparently pronotum with short, fine, recumbent setae.

Head subtrapezoidal, with fine (smaller than one compound eye facet) and rather dense punctation, distance between punctures slightly larger than diameter of one puncture; narrower than anterior pronotal margin; epistome with widely rounded apical margin; fronto-epistomal suture indistinct, slightly impressed laterally. Frons slightly convex, about 2.8× as wide as eye width (between anterior compound eye margins). Genae regularly rounded; outer margin of head without emargination between gena and epistoma. Compound eyes large, convex, reniform, oblique in dorsal view, constricted by genal cantus; dorsal part smaller than ventral part. Tempora very short, narrowed toward neck. Apical maxillary palpomeres securiform, elongate, apical margin obliquely truncate; apical labial palpomeres weakly triangular, subcylindrical.

Antennae robust, short, reaching approximately posterior one-fourth of pronotal length, insertion concealed by genae; antenna without club but with antennomeres gradually widening to apex subsequent to antennomere 6; scape and pedicel poorly visible in examined specimen, pedicel cylindrical, apparently almost as long as wide, slightly narrower than scape; antennomere 3 subcylindrical, elongate, about 2.1× as long as wide, slightly dilated apically; antennomere 4 conical, elongate, about 1.7× as long as wide, dilated apically; antennomeres 5–10 weakly to distinctly serrate, antennomeres 5–6 slightly elongate, antennomere 7 nearly as long as wide, antennomeres 8–10 transverse, 1.3–1.5× as wide as long; antennomere 11 rounded, as long as wide; relative length ratios of antennomeres 1–11 equal to?:?:17:15:14:13:13:11:11:11:15.

Pronotum trapezoidal, strongly transverse, 1.95× as wide as long, widest at mid-length. Lateral margins slightly rounded, almost parallel-sided in posterior half of pronotum, and in anterior half distinctly narrowed toward anterior margin; anterior margin rounded; base bisinuate; all margins bordered. Anterior and posterior angles nearly rectangular. Disc slightly convex, lateral sides flattened. Pronotal punctation fine and rather dense, distance between punctures larger than diameter of one puncture; punctures on disc less conspicuous, smoothed. Prosternum with dense rugosity. Prosternal process narrow, about 0.35× as wide as diameter of procoxa; with longitudinal groove along lateral sides; roundly bent down and weakly projecting posterior to procoxae.

Scutellum moderately large, strongly transverse, narrowly subpentagonal, with widely rounded apical margin.

Elytra elongate-oval in shape, subparallel-sided, about 1.8× as long as wide, widest in posterior one-third of length, and 3.3× as long as pronotum; elytral base about as wide as base of pronotum; with weakly visible striae of fine, dense, round punctures; first (epipleural) stria tapers to end before the elytral apex and does not join the sutural stria at apex; scutellar striole present; interstriae much wider than striae, slightly convex (nearly flat on disc), densely micropunctate; humeral angles distinct, obtuse. Epipleura wide, not reaching elytral sutural angle, abruptly tapering and ended anterior to elytral apex, widest at humeri and gradually narrowing posteriad, slightly impressed, apparently covered with fine punctation. Metathoracic wings present. Metepisterna with fine, dense punctation; lateral margins almost straight, anterior margin oblique. Metaventrite slightly convex, shiny, with very fine and sparse punctation on disc and with more conspicuous punctation laterally.

Legs moderately long and rather slender, with fine and dense punctation; moderately pubescent with fine, recumbent setae. Femora spindle-shaped, flattened, ventrally with longitudinal groove for tibiae reception. Tibiae thin and almost straight, slightly dilated apically; with at least one visible apical spur; without modifications. Tarsi long, rather slender; tarsomere 1 with dense, fine, golden setae ventrally, not arranged in two rows; relative length ratios of mesotarsomeres 1–5 equal to 3:2:2:2:5. Tarsal claws symmetrical, simple, large, strongly divergent.

Abdomen with five visible ventrites, ventrites 1–3 equal in length, intersegmental membranes between ventrites 3–5 present; covered with fine, dense punctation, and with longitudinal wrinkles laterally; glabrous.

Etymology. The epithet of this new species is patronymic, named in the memory of the Hungarian entomologist Ottó Merkl (1957–2021), our friend and colleague, and a renowned specialist on Tenebrionoidea of the world.

Differential diagnosis. See the diagnosis of the subgenus.

Figures

FIGURE 1. Metaclisa (Trichometaclisa) ottoi sp. nov. (holotype, Baltic amber), habitus: A—dorsal view; B—ventral view; C—lateral view (es—epipleural stria taper to end before the elytral apex). Scale bars = 3 mm (A–C).

FIGURE 2. Metaclisa (Trichometaclisa) ottoi sp. nov. (holotype, Baltic amber), details of structure: A—elytral pubescence; B—first mesotarsomere (t1), plantar surface (fine golden setae, not arranged in two rows); C—anterior part of body, ventrally (pp – prosternal process); D—the middle of body, ventrally; E—head and right antenna, dorsally; F—apex of abdominal part, ventrally (e-w—widened part of epipleura, e-n—narrow part of epipleura, which is sharply tapered before apex). Scale bars = 0.5 mm (A, B), 2 mm (C, D), 1 mm (E, F).