Bitoma glaesisepulta, Alekseev, 2015

Alekseev, Vitalii I., 2015, New cylindrical bark and ironclad beetles (Coleoptera: Zopheridae) from Baltic amber, Baltic Journal of Coleopterology 15 (1), pp. 17-24 : 20-22

Bitoma glaesisepulta sp. nov.

( Figs. 3–4 )

Material examined: Holotype Nr. AWI-010 [ CVIA], sex unknown. The beetle is included in a polished piece of transparent amber, orange in color (measurements 15 mm x 6 mm x 4.5 mm). The amber was not subject to any fixation. The syninclusions are represented by four fagaceous stellate hairs.

Type strata: Baltic Amber. Eocene.

Type locality: Baltic Sea coast, Yantarny settlement [formerly Palmnicken], the Kaliningrad region, Russia .

Differential diagnosis: The specimen under study is assigned to the tribe Synchitini due to the following morphological characters: metacoxae narrowly separated; tarsi without dilated segments; antennae glabrous, lacking scale-like setae, 11–segmented with distinct club; procoxal cavities open; femora punctuated; apex of the protibiae without spine. The following characters correspond to the genus Bitoma : parallel-sided cylindrical body; 2– segmented antennal club; dorsal surface without setae; subequal antennomeres III and IV; nonproduced anterior pronotal angles; elytra without tubercles. Bitoma glaesisepulta sp. nov. can be distinguished by the longitudinal pronotum with subparallel sides and three shallow depressions, the longitudinally rugose head and anterior pronotal margin, the absence of elytral costae and the reduced interfacetal setae. The new species differs from all extant congeners of Palaearctic and Nearctic in the non-carinate pronotal disc.

Description:

Body: TL = 2.75 mm, EW = 0.84 mm, elongate (TL/ EW = 3.2), glabrous, cylindrical, uniformly dark brown ( Fig. 3–4 ).

Head: 2.5 times wider than long; anterior clypeal margin densely coarse and irregular sculptured, rounded. Surface covered with longitudinal rugosity. Eyes entire, mediumsized, well-developed, finely faceted. Interfacetal setae not apparent (by x56 magnification). Antennae 11–segmented, short, reaching the basal angles of the pronotum, with 2–segmented distinct club and thickened cylindrical scape and pedicel.

Prothorax: PL = 0.9 mm, PW = 0.7 mm, elongate ( PL / PW = 1.3); sides subparallel, margined laterally and basally; anterior and posterior angles rounded, nearly obsolete; anterior and posterior margins arcuate; lateral margin slightly flattened. Pronotal disc convex; longitudinally rugose apically; coarsely, densely punctuated on the middle, with a longitudinal shallow impression medially and a pair of shallow impressions laterally before the middle.

Hypomeron and prosternum with dense large coarse rounded punctures.

Scutellum: rounded, oval, transverse (almost twice wider than long), without distinct punctures.

Elytra: EL = 1.63 mm, EW = 0.85 mm, elongate, nearly parallel-sided, wider than pronotum, jointly rounded apically, with lon gitudinal striae dorsally and irregular punctuation laterally. Each elytron with 8 rows of strial punctures, their intervals narrow; each puncture large, rounded, separated by a distance 0.3–0.4 times as wide as diameter; scutellary str iole pr esen t. Outer mar gin s of elytr a flattened. Epipleura present, well developed, wide, reaching the elytral apex. Hind wings present.

Abdomen: with five visible, similarly articulated ventrites having relative lengths 10-10-7-6-10. Surface without apparent setation, with irregular dense punctuation; intervals between punctures 1–2 times as wide as their diameter. Intercoxal process of the ventrite I triangular, narrow.

Legs: short, robust. Procoxal and mesocoxal cavities rounded and externally open, metacoxal cavities transverse, closed. Metacoxae narrowly separated. Femora wide. Tarsal formula 4-4-4. Length of apical tarsomeres equal to combined length of tarsomeres I–III; tarsal claws simple, large, equal in size, almost one-half as long as the apical tarsomeres.

Derivatio nominis: The epithet of the new species is a combination of Latin “glaesum” [amber] and “sepultus, -a, -um” [buried], that is “buried in amber”.

Figures

Fig. 3. Bitoma glaesisepulta sp. nov. Habitus.: a) Lateral view; b) Ventral view; c) Dorsal view

Fig. 4. Bitoma glaesisepulta sp. nov. Dorsal habitus, reconstruction