Isomira (Mucheimira) lobanovi, Nabozhenko & Bukejs, 2021

Nabozhenko, M. V. & Bukejs, A., 2021, A new species and a key to Isomira Mulsant, 1856 (Coleoptera: Tenebrionidae: Alleculinae) from Eocene Baltic amber, Caucasian Entomological Bulletin (Caucas. entomol. bull.) 17 (1), pp. 51-56 : 52-54

Isomira (Mucheimira) lobanovi sp. n.

( Figs 1–6, 9 )

Material. Holotype, ♂ ( MAIG), collection number “6704” (ex. coll. Jonas Damzen JDC 9351): a complete beetle with the partially exposed metathoracic wings and apical portion of aedeagus is included in a transparent, yellow amber piece with approximate dimensions of 35 × 13 × 12 mm; preserved without supplementary fixation. Organic syninclusions: few small stellate fagacean trichomes.

Type stratum. Baltic amber from Eocene amberbearing Blue Earth layers; a predominantly Bartonian age has been interpreted for the extinct central European resin-producing forests [ Szwedo, Sontag, 2009; Bukejs et al., 2019].

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

Description. Measurements: body length 4.5 mm, body maximum width 1.9 mm; pronotum length 0.7 mm, pronotum maximum width 1.5 mm; elytral length 3.5 mm, elytral maximum combined width 1.9 mm.

Body elongate-oval, subparallel sided, slightly convex; dorsal surface regularly pubescent with recumbent, short setae ( Fig. 1 ).

Head with coarse and dense punctation, distance between punctures smaller than one puncture diameter; anterior margin emarginate, about 2 times as wide as frons between eyes; lateral margins widely sinuate between epistoma and genae. Frons separated from epistoma by suture-shaped impressed wrinkle. Compound eyes large, convex, reniform, widely emarginate at inner margin; wider dorsally and narrower ventrally; dorsal ocular index 15; eyes ventrally reaching to laryngeal emargination. Maxillary palpomere 1 small, about 0.4 times as long as palpomere 2; palpomere 2 subconical, slightly dilated apically, elongate, 2.7 times as long as wide; palpomere 3 nearly as long as wide, slightly dilated apically, with oblique apical margin; palpomere 4 securiform, apical margin strongly obliquely truncate ( Fig. 4 ), elongate, 2.1 times as long as wide; length ratios of maxillary palpomeres 1–4 equal to 8: 20: 11: 28. Antennae long (nearly reaching middle of abdominal ventrite 3), moderately serrate, inserted between and close to anterior inner margin of eyes ( Fig. 9 ); scape cylindrical, 1.3 times as long as wide; pedicel cylindrical, 1.2 times as long as wide, slightly narrower and shorter than scape; antennomere 3 subconical, about 1.5 times as long as wide, slightly dilated apically, with oblique apical margin; antennomeres 4–10 elongate, dilated apically, subequal in length and shape, joined asymmetrically; antennomere 11 elongate, with pointed apex; length ratios of antennomeres 1–11 equal to 11: 9: 11: 32: 36: 36: 36: 36: 32: 29: 41.

Pronotum bell-shaped, strongly transverse, 2.1 times as wide as long, widest at middle. Lateral margins very weakly rounded, almost parallel sided in posterior half, and in anterior half they sharply narrowed to anterior margin; anterior margin weakly rounded; base straight laterally and slightly rounded at middle. Anterior angles rounded; posterior angles weakly obtuse. Anterior margin with distinct bead medially; posterior margin with distinct bead; lateral margins with narrow bead. Pronotal punctation fine and dense, not rasp-like, distance between punctures distinctly smaller than a puncture diameter; interspaces microsculptured. Prohypomera and prosternum before procoxae apparently impunctate. Prosternal process narrow, about 0.5 times as wide as diameter of procoxa.

Scutellum moderately large, subtriangular, with slightly convex lateral margins, transverse, 1.4 times as wide as long, punctate.

Elytra elongate-oval, subparallel sided, widest at middle, 4 times as long as pronotum; with weakly visible striae of fine, longitudinal punctures; interstriae densely covered with fine rasp-like punctation. Epipleura wide, not reaching elytral sutural angle, sharply narrowing before apex, near middle of abdominal ventrite 5; covered with fine punctation. Hind wings present. Mesepisterna and mesepimera with coarse, sparse, round punctures, distance between punctures greater than one puncture diameter. Metepisterna and metaventrite with coarse, moderately dense, round punctation, distance between punctures 0.5–2 times as a puncture diameter (disc of metaventrite and anterior portion of metepisterna with sparser and finer punctures) ( Fig. 5 ).

Legs long and slender, with fine and dense punctation; regularly pubescent with fine, recumbent setae. Femora clavate, flattened. Tibiae thin and straight (pro- and mesotibiae weakly curved in lateral view); with simple fine suberected setiform spines (not strong sparse spines); with two short apical spurs of subequal length. Length ratios of tarsomeres (from basal to apical) equal to 5: 4: 3: 3: 8 (protarsi), 9: 5: 4: 3: 8 (mesotarsi), 14: 5: 3: 8 (metatarsi). Tarsal claws serrate, symmetrical, large, strongly divergent. Protarsal claws with four teeth.

Abdomen covered with fine dense punctation and fine recumbent setation; length ratios of abdominal ventrites equal to (?)5: 6: 5: 4: 4 (medially).

Apical piece of aedeagus narrowly-triangular, with pointed apex ( Fig. 6 ).

Differential diagnosis. This species belongs to the subgenus Mucheimira by the very large eyes and short distance between eyes in male and presence of subequal and short antennomeres 2 and 3. The subgenus Mucheimira is characterized by sexual dimorphism in ocular index between male and female [ Novák, 2016]. The ocular index of female is not defined, but I. lobanovi sp. n. is very close to I. (Mucheimira) avula by many characters and similar form of apical piece of aedeagus and differs only by the structure of antennae. As a result, the new species is included into the mentioned subgenus. Differences between I. avula and I. lobanovi sp. n. are indicated in the key below. The new species differs from all extant congeners in the distinctly serrate antennae and from I. (Mucheimira) stoetzneri Muche, 1981 and I. (Mucheimira) murzini Novák, 2009 additionally in the shorter body (4.5 mm, unlike more than 7 mm in both mentioned species [ Novák, 2009, 2014]). Apical piece of aedeagus subacute and slightly curved in lateral view, the most similar to that in I. (Mucheimira) sichuanica Novák, 2009 [ Novák, 2009: fig. 19].

Etymology. The species is named in memory of Dr Andrei Lvovich Lobanov, known specialist on Cerambycidae and the founder of the largest coleopteran website “Beetles and coleopterists”.

Figures

Figs 1–9. Isomira (Mucheimira) spp. from Baltic amber, males, habitus and details of structure. 1–6, 9 – I. lobanovi sp. n.; 7, 8 – I. avula. 1 – habitus, dorsal view; 2 – habitus, lateral view (left side); 3 – habitus, lateral view (right side); 4 – head, prothorax and sclerites of pterothorax, latero-frontal view; 5 – abdomen, middle and hind tibiae; 6 –apical piece of the aedeagus, lateral view; 7 – right antenna, view from lateral side; 8 – left antenna, view from below; 9 – right antenna, view from above. Рис. 1–9. Isomira (Mucheimira) spp. из баΛтийского янтаря, самцы, общий виΑ и ΑетаΛи строения. 1–6, 9 – I. lobanovi sp. n.; 7, 8 – I. avula. 1 – габитус, виΑ сверху; 2 – габитус, виΑ сбоку (Λевая сторона); 3 – габитус, виΑ сбоку (правая сторона); 4 – гоΛова, проторакс и скΛериты птероторакса, виΑ сбоку и спереΑи; 5 – брюшко, среΑние и заΑние ноги; 6 – апикаΛьная ΑоΛя эΑеагуса, виΑ сбоку; 7 – правая антенна, виΑ с боковой стороны; 8 – Λевая антенна, виΑ снизу; 9 – правая антенна, виΑ сверху.