Dignomus francescovitalii, Bukejs & Bellés & Alekseev, 2018

Bukejs, Andris, Bellés, Xavier & Alekseev, Vitalii I., 2018, A new species of Dignomus Wollaston (Coleoptera: Ptinidae) from Eocene Baltic amber, Zootaxa 4486 (2), pp. 195-200 : 196-198

Dignomus francescovitalii sp. nov.

( Figs 1–6 )

Type material. Holotype: collection number 1045-1b [CCHH], adult, probably a male. A practically complete beetle (right protarsus lacking) with partially exposed genitalia, included in a small, transparent yellow amber piece embedded in block of GTS-polyester resin with overall dimensions 9×9× 4 mm. Syninclusions: one stellate Fagaceae trichome.

Type strata. Baltic amber, Ypresian to Priabonian, Eocene, 56¯33.9 Ma.

Type locality. Baltic Sea coast, the Samland Peninsula, the Kaliningrad Region, Russia.

Etymology. Patronymic, this new species is dedicated to our colleague and leading researcher of amber Cerambycidae, Dr. Francesco Vitali ( Luxembourg) .

Description. Body length 2.3 mm, maximum width about 1.4 mm; body shape ovoid; body color (as preserved) unicolorous black.

Head hypognathous, turned downwards and not visible in dorsal view, evenly convex; frons with sparse erect setae, and with transverse row of erect setae above antennal pits; vertex glabrous, shiny and apparently impunctate; antennal pits contiguous, interantennal space with a sharp, narrow carina.

Compound eyes relatively small, hemispherical, convex, entire, with well differentiated facets, apparently without ommatidial setae; distance between compound eyes nearly equal to 1.6× diameter of one eye.

Antennae filiform, with eleven antennomeres, exceeding in length half of the elytra; densely pubescent and with sparse, semierect setae, except antennomere 11 which has only short and recumbent pubescence; scape subcylindrical, robust, about 2× as wide and 1.3× as long as pedicel, antennomeres 2–10 subequal in shape and size, elongate, slightly dilated apically, antennomere 11 spindle-shaped; relative length ratios of antennomeres 1– 11 equal to 10-6-6-6 -6-7- 7-7-7-8-12. Last maxillary palpomere cylindrical.

Pronotum slightly transverse, about 1.15× as wide as long; with distinct constriction in posterior one-fourth; covered with small punctures, each puncture bearing seta; with elevated discal protuberance widely divided medially by longitudinal groove, protuberance becoming concave postero-medially and narrowly reflexed at lateral sides, which show an acute, triangular, small projection; whole pronotum with small dense granules and semierect setae, distance between granules being less than the diameter of one granule; two lateral sides of discal protuberance with very dense, long, rufous hairs.

Scutellum small, slightly transverse, semioval, densely pubescent.

Elytra sub-ovoid, convex, about 1.2× as long as wide, with visible humeral calli; each elytron with five small spots of rufous scale-like hairs: three round shaped spots at elytral base, and two oval shaped spots on disc. Elytral punctures small, arranged in 10 striae that extend along entire length of elytron, punctures round to oval showing medial constriction (punctures of striae 9–10); intervals flat, with sparse heterogeneous pubescence.

Pro-, meso- and metathotax densely pubescent, with moderately large, deep, round punctures; prosternal intercoxal process wide, about 0.7× as wide as diameter of procoxa, slightly convex, with lateral margins parallel; metathoracic ventrite almost flat, medially and slightly convex laterally, distance between punctures distinctly larger than diameter of one puncture; metepisternum about 3.9× as long as wide, with row of punctures at interior lateral margin, slightly widened anteriorly and gradually narrowed posteriorly, anterior margin oblique, lateral margins nearly straight.

Legs long, moderately robust, densely pubescent. Procoxae subglobose, separated by about 0.7× procoxal diameter; mesocoxae subglobose, distinctly separated by almost one mesocoxal diameter; metacoxae narrow, transverse, with groove for reception of metafemora. Femora clavate, with few erect setae ventro-apically. Tibiae almost straight, slightly dilated apically, nearly as long as tibia. Tarsi poorly visible because of beetle location in amber piece; metatarsi about 0.6× as long as metatibia. Claws thin, free and simple.

Abdomen with five visible ventrites, densely pubescent, with sparse, fine semierect setae (distinctly visible on ventrite 5), sparsely punctured (punctures distinctly smaller than metathoratic punctures); abdominal sutures distinct in all their length; relative length (laterally) ratios of ventrites 1–5 equal to 10-12-10-5-8.

Genitalia exposed but poorly defined, although apparently corresponding to male aedeagus with median lobe and parameres slender and symmetrical, as usual in extant species of the genus Dignomus (see Bellés 1996).

Diagnosis. Dignomus francescovitalii sp. nov. assigned to Dignomus irroratus species-group based on a combination of the following morphological characters (sensu Bellés 1996): the structure of pronotum with discal protuberance showing subparallel sides, convex but not very elevated, widely divided medially by longitudinal groove, and with triangular lateral projections located behind the discal protuberance in lateral view. The characteristic sub-ovoid elytra clearly distinguishes this new species from others of the group. Only D. subelongatus (Pic, 1917) from East Africa ( Somalia) has similar sub-ovoid elytra, but differs from new species by pronotum with discal protuberance more elevated and elytra more elongated.

Dignomus francescovitalii sp. nov. distinctly differs from D. regiomontanus (described from a Baltic amber) in pronotal structure: the latter species has pronotum with discal longitudinal protrusion flanked by groove on each side, but in new species pronotum with elevated discal protuberance widely divided medially by longitudinal groove, protuberance becoming concave postero-medially and narrowly reflexed at lateral sides. Additionally, these species can be distinguished by body length ( D. regiomontanus is 3.7 mm long; 2.3 mm in new species), eyes (large and with ommatidial setae in D. regiomontanus ; small, without ommatidial setae in new species), and antennae (slender, exceeding in length apex of the elytra in D. regiomontanus ; D. francescovitalii sp. nov. possesses comparatively shorter and thicker antennae).

Figures

FIGURES 1–3. Dignomus francescovitalii sp. nov., holotype: 1—habitus, right lateral view; 2—habitus, left lateral view; 3— habitus, dorsal view. Scale bars = 0.5 mm.

FIGURES 4–6. Dignomus francescovitalii sp. nov., holotype: 4—details of forebody, lateral view; 5—abdomen, lateral view; 6—left antenna. Scale bars = 0.25 mm.