Anthobium alekseevi Shavrin & Yamamoto, 2020

Shavrin, Alexey V. & Yamamoto, Shuhei, 2020, A remarkable new species of the rove beetle genus Anthobium Leach, 1819 from Eocene Baltic amber (Coleoptera, Staphylinidae, Omaliinae), ZooKeys 973, pp. 89-101 : 89

† Anthobium alekseevi Shavrin & Yamamoto sp. nov. Figures 1-4 , 5, 6 , 7, 8 , 9-13 , 14-19

Type material examined.

Holotype: male, complete specimen as inclusion in a piece of small yellow Baltic amber, 11.0 mm × 0.7 mm × 0.5 mm in size (Figs 1 , 2 ), with glued small paper on side of an amber labeled “AWI148” and additional labels within a plastic envelope: "AWI-148 | Omaliinae | gen. nov. | (mesotibia!)" <handwritten>, " HOLOTYPE | Anthobium | alekseevi sp. nov. | Shavrin A. & Yamamoto S. des. 2020" <red rectangular label, printed> (PIN).

Preservation.

The specimen is poorly visible because it is partially covered with white microbubbles, and some details of the structure of the body are not visible: head, median portion of pronotum and scutellum, ventral side of the body and abdomen (Figs 1 , 2 ). The basal part of the abdomen ventrally is covered by left hind wing.

Locality and horizon.

Baltic amber from Kaliningrad Area, westernmost Russia; mid-Eocene (ca 44 Ma; Wappler 2005).

Description.

Measurements: maximum width of head including eyes: 1.30; length of head (from base of labrum to neck constriction along head midline in dorsal view): 0.75; ocular length: 0.40; length × width of segments III and IV of maxillary palpi: III: 0.15 × 0.10, IV: 0.30 × 0.10; length of antenna: 2.70; length of pronotum: 1.35; maximum width of pronotum: 1.75; sutural length of elytra from apex of scutellum to posterior margin of sutural angle: 2.60; length of elytron from basal to apical margin: 2.95; maximum width of elytra: 2.30; length of metatibia: 1.60; length of metatarsus: 0.80; maximum width of abdomen (at segment IV): 2.10; total length (from anterior margin of clypeus to apex of abdomen): ~5.40.

Body oblong, moderately wide, shiny (Fig. 3 ); body laterally as in Figures 5 , 6 , 9 , and 10 ; body dorsolaterally as in Figure 4 ; body ventrally as in Figures 11 and 12 ; forebody as in Figure 14 . Body and antennomeres 3-11, brown; legs and mouthparts reddish-brown; antennomeres 1 and 2 yellow-brown.

Head transverse (Figs 15 , 16 ), 1.7 times as wide as long; anterior portion of frons with obliquely elevated supra-antennal prominences and moderately wide impressions behind them; middle portion slightly elevated, with distinct, deep, narrow dorsal tentorial pits (grooves) in front of ocelli, diagonally stretching apicad to level of middle length of eyes; basal portion with distinct, narrow impression between ocelli; postocular ridge distinct, acute, located relatively close to posterior margin of eye, if see laterally (Figs 5 , 9 , 18 ). Eyes large, convex. Ocelli large, situated at about level of postocular ridges; distance between ocelli slightly shorter than distance between ocellus and posterior margin of eye (Figs 15 , 16 ). Labrum wide, transverse. Mentum and labium narrow, with distinctly elongate apical labial palpomere (Fig. 12 ). Preapical segment of maxillary palpus moderately long, 1.5 times as long as wide, and as wide as apical segment; apical segment about twice as long as preceding segment, from middle gradually narrowing toward apex (Figs 5 , 11 , 18 ). Gular sutures with shortest distance located at level of posterior third of eyes (Fig. 12 ). Antenna moderately short, exceeding apical third of elytra, with elongate antennomeres 5-10 and long preapical setae, antennomeres 3-11 covered by dense pubescence; basal antennomere moderately wide, 1.5 times as long as 2, antennomere 2 ovoid, about twice as long as wide and slightly shorter than 3, 3 and 4 as wide as 2, 5-7 slightly shorter than 4, 8 and 9 slightly shorter than 7, 10 distinctly shorter than 9, apical antennomere 1.6 times as long as 10, from middle gradually narrowed toward apex (Fig. 3 ).

Pronotum subrectangular, 1.2 times as wide as long, 1.3 times as wide as head, widest in middle, evenly rounded both anteriad and posteriad (Fig. 14 ); apical margin rounded, distinctly narrower than posterior margin; anterior angles widely rounded, slightly protruded anteriad; posterior angles obtuse; lateral edges bordered, without visible crenulation; disc with middle portion widely elevated, with indistinct, wide, semioval impression on mediobasal third, and lateral portions moderately wide, slightly explanate, each with deep pit in middle (Fig. 16 ). Laterobasal and basal portions of pronotum with dense and fine punctation (Fig. 3 ). Pronotal hypomeron and postcoxal process well developed; intercoxal process elongate and moderately wide; prosternum with distinct median carina (Figs 11 , 18 ). Scutellum large and wide, with rounded apex. Metaventrite wide, convex.

Elytra convex, slightly longer than wide, about twice as long as pronotum, indistinctly widened in middle, reaching basal margin of abdominal tergite VI, with widely rounded apical margins (Fig. 17 ); shoulders of elytra rounded; lateral portions narrow, explanate; surface of elytra without visible elevations. Punctation sparse and moderately small, each elytron with longitudinal rows of vague serial punctures in middle (Fig. 3 ). Hind wings fully developed.

Legs long (Fig. 7 ); procoxae wide, protruding ventrad, contiguous; mesocoxae large, convex; metacoxae strongly transverse; pro-, meso-, and metatrochanter relatively narrow, elongate (Figs 11 , 12 ); all femora widest at about middle, profemora slightly wider than meso- and metafemora; pro- and mesotibiae about as long as femora; protibiae covered with dense long setae; protarsomeres 1-5 as in Fig. 8 ; mesotibiae indistinctly curved in middle, inner side of each mesotibia with large and wide subtriangular, fin-shaped tooth in middle (Fig. 7 , arrows); meso- and metatibiae covered by very dense, long and strong setae (including apex of tooth on each mesotibia); metatibiae with additional very long setae; metatibiae distinctly longer than metafemora, slightly widened in about middle, covered by dense, strong and long setae, with a few additional spines around apical margin; all tarsi 5-segmented, all tarsi combined shorter than tibia; tarsomeres 1-4 with long and dense lateral setation; apical tarsomere about as long as preceding three tarsomeres together; tarsal claws simple, without modifications (Fig. 7 ).

Abdomen distinctly narrower than elytra (Fig. 17 ), from segment IV significantly narrowing apicad (Fig. 11 ); abdominal segment IX elongate. Abdomen ventrally as in Figures 11 and 12 .

Male. Protarsomeres 1-4 distinctly wide, with very long lateral setae (Fig. 8 ). Apical margin of abdominal tergite VIII rounded (Fig. 17 ). Apical margin of sternite VIII sinuate (Fig. 12 ).

Female unknown.

Etymology.

Patronymic, the species is named to honor our colleague Vitalii I. Alekseev (Kaliningrad), great contributor to the knowledge of the fossil beetle fauna from Baltic amber.

Figures

Figures 1 - 4. Anthobium alekseevi sp. nov. 1, 2 amber specimen with inclusion 3 habitus, dorsal view 4 habitus, dorsoventral view. Scale bar: 1.0 mm (3, 4).

Figures 5, 6. Anthobium alekseevi sp. nov., habitus (lateral view). Scale bar: 1.0 mm.

Figures 7, 8. Anthobium alekseevi sp. nov. 7 legs 8 protarsus. Scale bars: 1.0 mm (7); 0.1 mm (8). Abbreviations: pt 1 - pt 5 = protarsomeres 1 - 5.

Figures 9 - 13. Habitus of Anthobium alekseevi sp. nov. 9, 10 lateral view 11, 12 ventral view 13 dorsal view. Scale bar: 1.0 mm.

Figures 14 - 19. Anthobium alekseevi sp. nov. 14 forebody, dorsal view 15 head, apical portion of pronotum and legs, frontal view 16 head, pronotum and antenna, dorsal view 17 elytra and abdomen, dorsal view 18 head and thorax, lateroventral view 19 apical portion of elytra, abdomen and legs, posterodorsal view. Scale bar: 1.0 mm.