Melipriopsis baltica Kirejtshuk et Bukejs, 2023

Kirejtshuk, Alexandr G. & Bukejs, Andris, 2023, A new species of Melipriopsis Kirejtshuk, 2011 (Coleoptera: Nitidulidae: Meligethinae) from the Eocene Baltic amber, Zootaxa 5230 (2), pp. 238-244 : 239-243

Melipriopsis baltica Kirejtshuk et Bukejs , sp. nov.

( Figs 1–7 )

LSID urn:lsid:zoobank.org:act:B631F9C3-1D89-4BF8-AEA1-758EE443BC8A

Type material. Holotype: Nr. 6897 [ MAIG] (ex coll. Jonas Damzen JDC-9007); adult, female. A rather complete beetle (right anterior leg is missing) with completely exposed ovipositor included in a transparent, yellow amber piece, which has approximate dimensions of 13× 7 mm and a maximum thickness of 1 mm; preserved without supplementary fixation. Anterior portion of head obscured by milky opacity. Syninclusions: two specimens of Aphididae (Hemiptera) , one stellate trichomes of Fagaceae , and a few detrital particles .

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

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

Description. Measurements: body length 3.8 mm; pronotal length 1.1 mm, pronotal maximum width 2.0 mm; elytral length 2.5 mm, elytra maximum combined width 2.0 mm; length of exposed ovipositor 0.7 mm. Body shape widely oval, subparallel-sided in dorsal outline, moderately convex dorsally and slightly convex ventrally; integument with fine, short, subrecumbent setae, pronotal and elytral lateral margins and pygidium with rather dense cilia; uniformly dark brown (as preserved) and with plumbeous lustre on dorsal surface.

Punctation: head with small punctation, puncture diameter slightly smaller than eye facet diameter, distance between punctures distinctly less than diameter of one puncture, interspaces microreticulate; pronotum and elytra with more or less smaller and significantly sparser punctation, distance between punctures equal to 0.75-1.5× puncture diameter, interspaces with obliterated microreticulation to alutaceous; sculpture of thoracic sclerites with finer and more or less sparser punctation and more distinct microreticulation; abdominal ventrites with slightly smaller and sparser punctation than that on metaventrite, interspaces with microreticulation; pygidium densely and finely punctate to microtuberculate.

Head with frons weakly convex. Eyes small, with small facets, interocular distance about 4× transverse diameter of eye. Mentum subtrapezoidal, 2.5× as wide as long and slightly widened anteriad. Antennal grooves distinct along inner margin of eye, slightly curved and rather short; postocular depression indistinct. Antennae 11- segmented with 3-segmented compact club; about 0.65× as long as head width (including eyes), with sparse erect setae; scape subcylindrical, about 2.5× as long as wide, about 1.3× as long as pedicel; pedicel cylindrical, 2.0× as long as wide; antennomere 3 cylindrical, slightly longer than antennomere 4; antennomeres 4–5 subcylindrical, slightly dilated apically, nearly as long as wide; antennomeres 6–8 thickened apically, transverse; antennomeres 9–11 forming compact club, flattened, about 0.3× as long as antennomeres 1–8 combined, about 2.5× as wide as long; antennomere 11 with subacute apex, nearly as long as wide; relative length ratios of antennomeres 1–11 equal to 8:6:5:3:3:3:3:3:5:4:8.

Pronotum subrectangular, transverse, 1.8× as wide as long, widest at base and slightly narrowed anteriad; with evenly convex disc and gently sloping at sides. Posterior margin weakly bisinuate, with distinct, narrowly bordered along middle; lateral margins weakly rounded, subparallel, with narrow bordering; anterior margin weakly bisinuate in dorsal view, apparently not beaded. Posterior angles distinct, obtuse, slightly projecting posteriad; anterior angles rounded, slightly projecting anteriad. Prosternum with disc convex; intercoxal prosternal process about 0.9× as wide as width of antennomere 10, flat, slightly dilated in apical one-fourth forming arrow-like apex, distinctly bordered along entire length, with rounded apex.

Scutellar shield transverse, suboval to subpentagonal and with widely rounded apex.

Elytra elongate, about 1.25× as long as wide combined, very widely arcuate at sides, with maximum width at mid length, 2.3× times as long as pronotum, at base nearly as wide as pronotum; evenly convex at disc and gently sloping at sides; lateral margins narrowly bordered; adsutural lines distinct in distal half; apices very widely rounded to subtruncate. Pygidium exposed, slightly convex, with widely rounded apex. Epipleura moderately wide and about as wide as antennal club. Mesoventrite apparently subflattened medially. Metaventrite slightly convex, with shallow medial impression; postmesocoxal line distinct, arcuately deviating at outer end of mesocoxae; posterior margin between metacoxae angularly excised.

Legs long and moderately thick. Procoxae about 2.3× as wide as long; mesocoxae somewhat more narrowly separated than procoxae; metacoxae 2.1× as wide as long; all coxae distinctly separated, distance between metacoxae about 2× as distance between mesocoxae. Femora widened medially, moderately flattened, about 1.9× as wide as prosternal process maximum width. Tibiae subtriangular, distinctly dilated and widened apically, slightly shorter than femora and slightly narrower than antennal club; protibiae with fine crenulation along outer margin; meso- and metatibiae with one row of dense and short setae along outer margin; apical spurs short and stout. Tarsi long, about 0.7× as long as tibia; protarsi apparently 0.5× as wide as prosternal process; tarsomeres 1–3 slightly dilated apically; pro- and mesotarsomere 5 longest, slightly curved. Tarsal claws simple, narrow, long.

Abdomen nearly flat; ventrite 1 longest, slightly longer than ventrites 2–4 combined, submetacoxal line situated closely to posterior edge of metacoxal cavity; ventrite 5 (hypopygidium) subtruncate, without impression basally; relative length ratios of ventrites 1–5 equal to 35:9:10:12:28 (medially).

Ovipositor ( Figs 6–7 ) strongly turned anteroventrally and only its upper side somewhat observable (because of obscured amber matrix), comparatively long; valvifer moderately wide and slightly narrowing distally, its length apparently about half of total length; outer lobes of gonocoxites apparently rather short and wide (about 0.3× as long as inner lobes); inner lobes becoming narrow and rather sclerotized, subparallelsided before blunt apex; short styli located apically closely to each other and oriented distally.

Diagnosis. Melipriopsis baltica sp. nov. differs from the type species of its genus in the wider and less convex body, the markedly finer and denser punctation of the integument, the widely explanate pronotal and elytral sides, the presence of the plumbeous lustre on the upper body surface, the smaller and narrower antennal club, the slightly projecting pronotal anterior and posterior angles (the anterior angles not projecting and posterior ones significantly projecting in Melipriopsis rasnitsyni ), the shorter ultimate abdominal segment, and the narrower legs with particularly tarsi.

Etymology. The epithet is pointing on the origin of the holotype of this new species in Baltic amber.

Note. In general, beetle ovipositor is rarely fully exposed (extracted from abdomen), and the ovipositor of the holotype of Melipriopsis baltica sp. nov. is the first case among the fossil nitidulids. Many extant nitidulids of all phyletic lines possess a rather generalized structure of the ovitositor, including most meligethines.

Figures

FIGURES 1–3. Melipriopsis baltica sp. nov., holotype, No 6897 [MAIG], habitus: 1 – dorsal view; 2 –ventral view; 3 – right lateral view. Body length 3.8 mm.

FIGURES 4–5. Melipriopsis baltica sp. nov., holotype, No 6897 [MAIG]: 4 – head and prothorax with appendages, ventral view; 5 – habitus, oblique dorsolateral view. Body length 3.8 mm.

FIGURES 6–7. Melipriopsis baltica sp. nov., holotype, No 6897 [MAIG], ovipositor: 6 – dorsal view; 7 – dorso-lateral view. Length of ovipositor 0.7 mm. Abbreviation: st – styli.