Petalium bruteno, 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 : 13-15

Petalium bruteno sp. nov.

( Figs. 1–2 )

Type material. Holotype: collection number “6781” [ MAIG] (ex. coll. Jonas Damzen JDC 7645); adult, sex unknown. A complete beetle included in a transparent, yellow amber piece with approximate dimensions of 24 mm × 18 mm and a maximum thickness of 5 mm; preserved without supplementary fixation. Syninclusions: few stellate fagacean trichomes.

Paratype: collection number “6782” [ MAIG] (ex. coll. Jonas Damzen JDC 9805); adult, sex unknown. A complete beetle with partially exposed metathoracic wings included in a transparent, yellow amber piece with approximate dimensions of 51 mm × 22 mm and a maximum thickness of 9 mm; preserved without supplementary fixation. Syninclusions: two Brachycera (Diptera) apecomens, and few small gas vesicles .

Paratype: collection number “PET01” [ JHAC]; adult, sex unknown. A complete beetle included in a transparent, yellow amber piece with approximate dimensions of 40 mm × 18 mm and a maximum thickness of 9 mm; preserved without supplementary fixation. Syninclusions: organic small residues of soil and plants .

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. Holotype JDC 7645. Measurements: total body length about 1.46 mm; pronotum length 0.38 mm, pronotum maximum width 0.54 mm; elytra length 1.08 mm, combined maximum width of elytra 0.69 mm. Body elongate, subparallel-sided, convex; glabrous, elytra with very fine, inconspicuous recumbent pubescence; unicolorous brown-rufous (as preserved).

Head hypognathous, turned downwards and not visible in dorsal view; densely covered with coarse punctation, distance between punctures lesser than diameter of one puncture; frons wide, weakly convex, without carina or longitudinal impression. Compound eyes rather large, convex, oval, with inner margin slightly emarginate at antennal insertion, with distinct facets, without ommatidial setae, widely separated. Fronto-clypeal suture fine, slightly impressed. Labrum very small. Mandibulae large.

Antennae apparently with 11 antennomeres (antennomeres 1–4 not visible), clavate; antennomeres 5 and 7 widened, swollen, globose, nearly as long as wide; antennomeres 6 and 8 small, narrow, elongate, about 1.8× as long as wide, antennomere 8 about 0.5× as wide as antennomere 7; antennomeres 9–10 forming distinct club, that apparently longer than antennomeres 1–8 combined; antennomeres 9 and 10 elongate, conical, dilated apically, antennomere 9 about 2.4× as wide as and 2.4× as long as antennomere 8; antennomere 11 elongate oval with pointed apex, 2.5× as long as wide.

Pronotum convex, transverse, 1.4× 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 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, 1.6× 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 fine, round, regular, each elytron apparently with 10 rows; distance between punctures in rows equal to 1–2× diameter of puncture, distance between rows equal to 2–3× diameter of puncture; intervals wide, flat, covered with micropunctation. Metaventrite with convex disc; medial groove distinct in posterior one-fourth; densely covered with small punctation; anterior median lobe large, with oval excavation posteriolaterally for reception of mesotarsus.

Legs short, slender. Metacoxae narrow, strongly transverse, separated. Trochanters small, slightly elongate. Femora flattened, slightly dilated medially, carinate dorsally, with deep ventral groove for tibia reception; metafemora not extending beyond elytral lateral margins. Tibiae almost straight, narrow, slightly longer than femora. Tarsi pentamerous, short, shorter than tibia, tarsomeres subcylindrical; protarsi distinctly dilated; relative length ratios of protarsomeres 1–5 equal to 5-3-2-2-4. Pretarsal claws thin, simple, free, strongly divergent.

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).

Paratype 6782 [ MAIG] Body length is 1.42 mm. Sutures between abdominal ventrites almost straight. Otherwise, this specimen is similar in all visible morphological characters to holotype 6781 [ MAIG] .

Paratype PET01 [ JHAC]. Body length is 1.45 mm. Otherwise, this specimen is similar in all visible morphological characters to holotype 6781 [ MAIG]

Differential diagnosis. Petalium bruteno sp. nov. can easily distinguished from two dorcatomine ptinids described from Baltic amber, Stagetus arturi Háva & Zahradník, 2020 and Calymmaderus ambericus Háva & Zahradník, 2020 , in the metathoracic ventrite with broad rounded lobe, in another body form and elytral striation ( Calymmaderus ambericus has only three distinct striae on apex of each elytron only), distinctly longer ventrite 2 (as long as ventrites 3 and 4 combined).

Derivatio nominis. Noun in apposition. Bruteno (also Pruteno or Prutanis) is the mythologized Prussian cultural hero, elder brother of Widewuto, the first high priest (Kriwe-Kriwajto) of the pagan Prussians during the VI century.

Figures

Fig. 1. Petalium bruteno sp. nov., holotype, 6781 [MAIG], habitus:A – dorsal view; B – ventral view

Fig. 2. Petalium bruteno sp. nov., paratype, 6782 [MAIG], habitus: A – dorsal view; B – ventral view