Symphora glaesonauta, Alekseev & Bukejs, 2021

Alekseev, Vitalii Igorevich & Bukejs, Andris, 2021, Fossil Melandryidae (Coleoptera: Tenebrionoidea) from Eocene Baltic amber of the Sambian peninsula: new genus, six new species, new records and key to described taxa, Zootaxa 4965 (1), pp. 142-166 : 156-158

Symphora glaesonauta sp. nov.

( Figs. 7 , 9E )

Type material. Holotype: No “MMO 1 7657/1253” [ MWO], “* Holotype / Symphora / glaesonauta sp. nov. / Alekseev et Bukejs des. 2021” [red handwritten label]; adult, sex unknown. A complete beetle with partially exposed metathoracic wing included in a transparent, yellow-orange amber piece with approximate dimensions of 12 mm × 5 mm and a maximum thickness of 4 mm; preserved without supplementary fixation. Specimen not well-observable in dorsal view due to the form of amber piece. Organic syninclusions: few stellate fagacean trichomes.

Non-type specimen. No “MMO 1/43 7657/29” [ MWO]; adult, sex unknown, in process of defecation. Organic syninclusions are absent. A complete beetle with body length 3.25 mm, included in a transparent, small, yellow amber piece with approximate dimensions of 12 mm × 8 mm and a maximum thickness of 6 mm; preserved without supplementary fixation. Specimen is poorly visible due to location in amber piece and milky opacity; it is not included into any type series and is tentatively assigned to this species only.

No “4463/45” [ KRAM]; adult, sex unknown (probable female, but the apex of extruded genitalia is hidden by the cracks and layered structure of amber). Organic syninclusions are absent. A complete beetle with body length 2.81 mm, included in a partially transparent, yellow amber piece with approximate dimensions of 28 mm × 20 mm and a maximum thickness of 11 mm; preserved without supplementary fixation. Specimen is poorly visible due to location in amber piece; it is not included into any type series and is tentatively assigned to this species only.

Type stratum. Baltic amber from Eocene amber-bearing blue Earth layers, mostly Bartonian age is interpreted for the extinct central European resin-producing forests ( Bukejs et al. 2019).

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

Description. Measurements: body length 2.36 mm; pronotum length 0.36 mm; pronotum maximum width 0.5 mm; elytra length 1.86 mm; elytra maximum width 0.8 mm. Body oblong, subparallel, slightly convex dorsally and ventrally; dark brown, unicolorous; distinctly punctate and pubescent; pubescence almost recumbent dorsally and ventrally, with additional very sparse, erect setae on elytra.

Head prognathous, well visible in dorsal view, sparsely covered with shallow punctuation; frons and vertex slightly convex. Fronto-clypeal suture well-visible, impressed, arcuate. Compound eyes small, slightly emarginate at antennal base, prominent, rounded, almost hemispherical; facets distinct and fine, without intrafacetal setae; interocular distance at upper margin of eyes about 1.7× larger than diameter of one eye. Clypeus with small angulate projection. Maxillary palpi about 0.25× as long as antenna; with 4 palpomeres: palpomeres 1–3 small, subequal in size, nearly as long as wide, palpomere 4 largest and widest, subtrianqular, with slightly rounded angles. Antennal insertions concealed from above. Antennae filiform, with 11 uniform slender antennomeres, inserted close to anterior margin of eyes, pubescent, reaching posteriorly to one-fourth of elytra; antennomere 11 spindle-shaped with pointed apex. Ratio of relative lengths of antennomeres 1–11 = 7:5:7:7:7:6:6:6:5:5:5.

Pronotum transverse, 1.4–1.5× wider than long, widest at base; densely covered with rough punctuation, forming transverse rugosity laterally. Pronotal disc evenly convex, without distinct impressions at base.Anterior pronotal margin weakly convex (in dorsal view); posterior margin narrower than elytral anterior margin, weakly bisinuate, finely margined; lateral margins gradually narrowed anteriad. Lateral pronotal carina present in form of short carination laterally discernible at posterior pronotal angles only. Anterior pronotal angles rounded; posterior angles almost right-angled. Prohypomera weakly convex, sparsely covered with distinct punctuation. Procoxal cavities without fissure (trochantin not visible). Scutellar shield rather large, rounded, transverse, about 1.25× wider than long.

Elytra elongate, about 2.3–2.5× longer than wide, almost parallel-sided in anterior three-fourths, gradually narrowed in posterior one-fourth, about 5× longer than pronotum; elytral apices rounded separately; elytral punctuation irregular, distance between punctures 0.3-2.0× as one puncture diameter, punctuation denser and coarser anteriorly and medially. Epipleura narrow, widest at humeri and gradually narrowed posteriad, reaching posterior margin of abdominal ventrite 1. Metepisternum rather wide, slightly dilated anteriorly, with subparallel lateral sides, about 3× longer than maximum wide, punctate. Metaventrite with convex disc, punctate, distance between punctures larger to diameter of one puncture.

Legs slender, long. Procoxae contiguous, conical; mesocoxae roundish, separated; metacoxae elongate oval, transverse, narrowly separated. Femora weakly flattened. Tibiae subcylindrical, almost straight, slightly dilated apically, subequal in length to femora; paired metatibial spurs equal in size, about 0.5× as long as metatibial width at apex. Tarsi long and slender; tarsal formula 5-5-4; penultimate tarsomere of all legs bilobed; metatarsus nearly as long as metatibia, metatarsomere 1 slightly longer than one-half of metatibia; ratio of relative lengths of metatarsomeres 1–4 = 20:7:3:5. Pretarsal claws simple, falcate, symmetrical.

Abdomen with five visible ventrites of subequal length, punctate, distance between punctures punctures 0.5- 2.0× as one puncture diameter; ventrite 5 with rounded apical margin.

Etymology. The specific epithet glaesonauta is a compound noun formed from “glesum” (Latin word for amber) and “nauta” (Greek and also Latin word for sailor, seaman, boatman), meaning “sailed/floated in/with amber” and created analogously to the widely used “astronaut”, “aeronaut” or “cosmonaut”. It is used as a noun in apposition.

Differential diagnosis. Symphora glaesonauta sp. nov. differs from the Baltic amber fossil S. pollocki sp. nov. in: (1) base of pronotum without rounded basal impressions; (2) larger and less transverse scutellar shield (1.25× wider than long, in contrast to about 2.3× wider than long in Symphora pollocki sp. nov.); (3) comparatively shorter antennomeres 9–11; and (4) distinctly longer and dorsally less convex elytra (elytra is about 5× longer than pronotum in S. glaesonauta sp. nov., whereas it is about 3.5× longer than pronotum in S. pollocki sp. nov.).

Remark. The new fossil species (and other members of the genus Symphora ) superficially resemble Scraptiidae (the false flower beetles) which are very abundant in Baltic amber inclusions. Symphora glaesonauta sp. nov. and S. pollocki sp. nov. can be rapidly distinguished from scraptiids in not abruptly constricted posteriorly head capsule, in not strongly emarginate eyes (in contrast to Scraptia Latreille, 1807 ), in not flattened tibiae (in contrast to Anaspis Geoffroy, 1762 ), in pronotum narrower than elytral base, and in slender filiform antennomeres.

Figures

FIGURE 7. Symphora glaesonauta sp. nov., holotype, No MMO 1 7657/1253 MWO, habitus, right lateral view. Scale bar represents 1.0 mm.

FIGURE 9. Reconstructions of new fossil Melandryidae from Baltic amber:A—Electroxylita chronographica gen. et sp. nov.; B—Phloiotrya inmarinata sp. nov.; C—Microscapha kugelanni sp. nov.; D—Madelinia capillata sp. nov.; E—Symphora glaesonauta sp. nov. Not reproduced to the same scale, punctuation and setation are omitted.