Asiomira dubrovinae, Nabozhenko & Bukejs, 2021

Nabozhenko, Maxim V. & Bukejs, Andris, 2021, The first fossilized comb-clawed beetle of the genus Asiomira Dubrovina, 1973 (Coleoptera: Tenebrionidae: Alleculinae) from Baltic Amber and notes on the distribution of extant species of the genus, Zootaxa 5082 (2), pp. 177-184 : 178-181

Asiomira dubrovinae sp. n.

( Fig. 2 )

Type material. Holotype: collection number “6806” [ MAIG] (ex. coll. Jonas Damzen JDC9875”); adult, female. A rather complete beetle (antennomeres 9–11 of right antenna are separated) with exposed apical part of the ovipositor, included in a transparent, yellow amber piece with approximate dimensions of 64× 15 mm and a maximum thickness of 12 mm; preserved without supplementary fixation. Syninclusions: a damaged specimen of caddisfly (Trichoptera), a specimen of Hymenoptera, a large specimen of Brachycera (Diptera), three small specimens of Brachycera (Diptera), few small stellate trichomes of Fagaceae , few small detrital particles, and numerous gas vesicles.

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

Description. Measurements: body length 4.8 mm (measured dorsally from anterior tip of head to apex of elytron), maximum body width 1.8 mm (measured in anterior one-third of elytra); head length (in dorsal view) 0.2 mm, head width (across compound eyes) 0.8 mm; pronotum length 0.8 mm, maximum pronotum width 1.5 mm; elytron length 3.7 mm, elytron maximum width 0.9 mm

Body elongate-oval, subparallel-sided, slightly convex; integument dark brown with legs, antennomeres 1–2 and palpi paler, brown to rufous (as preserved); dorsal surface regularly pubescent with fine, recumbent, short setae.

Head finely and densely punctured, distance between punctures smaller than diameter of one puncture; lateral margins widely sinuate between epistoma and genae. Compound eyes large, convex, oval, narrowly and shortly emarginate at inner margin; slightly wider ventrally than dorsally; space between eyes wide, about 3× as wide as length of antennomere 2; dorsal ocular index 40.25. Maxillary palpomere 1 small, about 0.3× as long as palpomere 2; palpomere 2 cylindrical, strongly elongate; palpomere 3 cylindrical, 1.6 as long as wide; palpomere 4 between securiform and cultiform, apical margin strongly obliquely truncate, elongate, 2.7× as long as wide; relative length ratios of maxillary palpomeres 1–4 equal to ~3:~9:6:14. Labial palpi with 3 palpomeres, short and narrow; palpomere 2 subconical, slightly dilated apically, about 2× as long as wide; palpomere 3 elongate, 2.5× as long as wide, elongateoval with slightly obliquely truncate apex, 2× as long as palpomere 2; relative length ratios of labial palpomeres 1–3 equal to 3:3:6. Antennae rather long, reaching approximately anterior half of abdominal ventrite 1, serrate, inserted between and close to anterior inner margin of eyes; scape cylindrical, 1.3× as long as wide; pedicel subconical, slightly dilated apically, 1.2× as long as wide, narrower and shorter than scape; antennomere 3 subconical, slightly dilated apically, strongly elongate, about 3.2× as long as wide, about 2.6× as long as antennomere 2; antennomeres 4–10 elongate, dilated apically, subequal in length and shape, joined asymmetrically; antennomere 11 elongate, with pointed apex; relative length ratios of antennomeres 1–11 equal to 8:5:13:15:15:15:15:13:13:13:13.

Prothorax. Pronotum bell-shaped, transverse, 1.7× as wide as long, widest at base. Lateral margins evenly rounded, gradually narrowed from base to anterior margin; anterior margin weakly rounded; posterior margin weakly bisinuate, straight medially. Anterior angles rounded, not conspicuous; posterior angles roundly rectangular. All margins with distinct bead. Pronotal punctation small and dense (as head punctures), distance between punctures distinctly smaller than diameter of one puncture; interspaces microsculptured. Prothoracic hypomera and apparently prosternum densely and finely punctured.

Pterothorax. Scutellar shield moderately large, triangular, with rounded apex, transverse, 1.4× as wide as long, densely punctate. Elytra elongate-oval, about 2.1× as long as wide, nearly parallel-sided in anterior two-thirds and then weakly narrowed to apex, 4.1× as long as pronotum; densely punctured with fine irregular punctures, distance between punctures smaller than diameter of one puncture, interspaces microsculptured. Epipleura wide, with dense and fine puncturation, widest at humeri then slightly narrowed to level of the first abdominal ventrite and then widened to apex; apparently not reaching elytral sutural angle, sharply narrowing before apex, near middle of abdominal ventrite 5. Metepisterna and metaventrite with coarse, rather dense, round puncturation, interpuncture distance smaller than diameter of one puncture.

Legs long and slender, with fine and dense puncturation; regularly pubescent with fine, recumbent setae. Femora clavate, flattened. Tibiae thin and straight, slightly dilated apically; with simple fine suberected setiform spines (not strong sparse spines); with two apical spurs of subequal length. Tarsal formula 5-5-4; relative length ratios of tarsomeres (from basal to apical) equal to 15:6:5:4:9 (mesotarsi), 20:9:5:9 (metatarsi). Tarsal claws serrate, symmetrical, large, strongly divergent; protarsal claws apparently with four teeth.

Abdomen covered with fine and rather dense puncturation; relative length ratios of abdominal ventrites equal to 17:13:13:10:~11 (laterally).

Etymology. The species is named in memory of Margarita Dubrovina, who made a great contribution to the Palaearctic Alleculinae and the author of the description of the genus Asiomira .

Comparative diagnosis. The new species belongs to the subtribe Gonoderina of the tribe Alleculini based on the combination of the following characters ( Nabozhenko & Bukejs 2021): five abdominal ventrites, serrate antennae, and simple penultimate tarsomere (the majority of Alleculina have lobed or bilobed penultimate tarsomere). Additionally, the specimen has no distinct rows of deep strial punctures or clear impressed striae unlike the majority of gonoderine genera. The following combination of characters confirms the placement of the new fossil species to the genus Asiomira : the body slender, elongate (not oval as in Isomira ), weakly convex; the apical maxillary palpomere between securiform and cultiform, with the strongly obliquely truncated apical margin; antennomeres 4–10 serrate; antennomere 3 much longer than the antennomere 2; elytra subparallel, without striae; epipleura narrowed at the middle, at the level of the abdominal ventrite 1 and then widened to the elytral apex. The eyes of the new species are large but widely spaced (ocular index is near 40), which is typical for females. Diagnostic features of Asiomira in context of other Gonoderina were given by Novák (2016).

Asiomira dubrovinae sp. n. differs from its congeners by more serrate antennae and much longer antennomere 3, which is 2.65× as long as the antennomere 2, while in extant Asiomira species antennomere 3 is about 2× as long as antennomere 2. The new species has antennomeres 4–10 wider and more serrate, each antennomere is less than 2.5× as long as wide. Among extant Asiomira only two species, A. ophtalmica ( Seidlitz, 1896) and A. firjusana ( Dubrovina, 1973) have similar antennomeres. The new species is the most similar to A. ophtalmica by the shape of the pronotum ( Fig. 3 ) and the flattened pronotal disc on posterior angles, but can be distinguished by the smaller body length (4.8 mm in contrast to 6–8.12 mm in A. ophtalmica ), the antennomere 3 2.5× as long as the antennomere 2 (less than 2× in A. ophtalmica ), the antennomere 4 1.3× as long as the antennomere 3 (1.5× in A. ophtalmica ), the antennomere 3 not oblique distally, the pronotal punctation finer and sparser (interpuncture diameter larger than punctures in A. dubrovinae sp. n., but subequal in A. ophtalmica ).

Figures

FIGURE 2. Asiomira dubrovinae sp. n. from Baltic amber, female, holotype: A—dorsal view; B—right lateral view.

FIGURE 3. Asiomira ophtalmica, general view, Murgab, Turkmenistan (Zoological Institute of the Russian Academy of Sciences): A—male; B—female.