Petalium widewuto, Alekseev & Bukejs, 2021

Alekseev, Vitalii I. & Bukejs, Andris, 2021, Two fossil species of Petaliini White (Coleoptera: Ptinidae: Dorcatominae) from Eocene Baltic amber, Baltic Journal of Coleopterology 21 (1), pp. 11-18 : 15-17

Petalium widewuto sp. nov.

( Fig. 3 )

Type material. Holotype: collection number “6783” [ MAIG] (ex. coll. Jonas Damzen JDC 6378); adult, sex unknown.Almost complete beetle (right metatibia and tarsus are missing) with partially exposed metathoracic wings included in a transparent, yellow amber piece with approximate dimensions of 21 mm × 9 mm and a maximum thickness of 6 mm; preserved without supplementary fixation. Syninclusions: one small detrital particle, and few small gas vesicles.

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

Type locality. Baltic Sea coast, Yantarny settlement (formerly Palmnicken), Sambia (Samland) Peninsula, the Kaliningrad Region, Russia .

Description. In general appearance, characters of body and legs very similar to P. bruteno sp. nov. Measurements: total body length about 1.55 mm; pronotum length 0.35 mm, pronotum maximum width 0.54 mm; elytra length 1.20 mm, combined maximum width of elytra 0.69 mm. Body elongate, subcylindrical, convex, strongly retractile; apparently covered with sparse, very fine, inconspicuous recumbent pubescence; unicolorous brown-rufous (as preserved).

Compound eyes rather large, convex, roundish, with inner margin indistinctly emarginate at antennal insertion, with distinct facets, without ommatidial setae, widely separated by about 1.8× transverse diameter of eye. Fronto-clypeal suture fine, indistinct, slightly impressed. Labrum very small. Antennae, maxillary and labial palps not visible in examined specimen.

Pronotum convex, transverse, 1.5× as wide as long, with convex disc, margined, widest at base and narrowed anteriad, strongly constricted in anterior one-third, with transverse impression at anterior angles; covered with large and dense punctation, punctures smaller on disc and in anterior portion of pronotum, distance between punctures lesser than diameter of one puncture. Anterior pronotal angles subrectangular, slightly rounded, not visible in dorsal view; posterior pronotal angles widely rounded and barely marked. Lateral margins slightly rounded; posterior margin bisinuated with wide median lobe; anterior margin upturned, convex in dorsal view, arcuate in frontal view. Prohypomera slightly impressed, with dense and coarse punctation.

Scutellar shield small, transverse, 1.3× as wide as long, pentagonal with widely rounded apex, covered with small punctures.

Elytra elongate, 1.7× as long as wide, subparallel-sided, widest in posterior one-third, slightly tapered posteriad, with transverse impression in anterior one-fourth; humeri distinctly prominent. Elytral punctures large, round, regular, each elytron apparently with 10 rows; distance between punctures in rows equal to 0.3–1.0× diameter of puncture, distance between rows lesser than diameter of puncture; intervals narrow, flat, covered with microsculpture. Macropterous. Metaventrite with slightly convex disc; medial groove distinct in posterior one-fourth; densely covered with small punctation; anterior median lobe large, with oval excavation posterio-laterally for reception of mesotarsus.

Legs short, slender; fore legs not visible in examined specimen. Metacoxae narrow, strongly transverse, separated. Femora flattened, slightly dilated medially, carinate dorsally, with deep ventral groove for tibia reception; meso- and metafemora not extending beyond elytral lateral margins. Tibiae almost straight, narrow, slightly longer than femora. Tarsi pentamerous, short, shorter than tibia, tarsomeres subcylindrical.

Abdomen with five freely articulated, visible ventrites, covered with small and dense punctation; ventrite 1 with short, triangular intercoxal process, and with transverse excavation in anterior half for reception of metathoracic legs; ventrite 2 largest; ventrite 5 with widely rounded apical margin; sutures slightly concave. Relative length ratios of ventrites 1–5 equal to 13-16-9-7-9 (medially; including intercoxal process).

Differential diagnosis. Petalium widewuto sp. nov. is similar to P. bruteno sp. nov. in many visible characters, but can be distinguished from it in distinctly larger elytral punctation with distance between punctures in rows lesser, than one puncture diameter.

Derivatio nominis. Noun in apposition. Widewuto (also Videvutis, Vaidevutis, Witowudi or Waidewut) is the mythologized Prussian cultural hero, youngest brother of Bruteno, a legendary king of Prussians during the VI century.

Figures

Fig. 3. Petalium widewuto sp. nov., holotype, 6783 [MAIG], habitus: A – ventral view; B – dorsolateral view