Microbregma waldwico, Bukejs, Andris & Alekseev, Vitalii I., 2015

Bukejs, Andris & Alekseev, Vitalii I., 2015, A second Eocene species of death-watch beetle belonging to the genus Microbregma Seidlitz (Coleoptera: Bostrichoidea) with a checklist of fossil Ptinidae, Zootaxa 3947 (4), pp. 553-562 : 554-556

Microbregma waldwico sp. nov.

( Figs. 1–3 )

Type material. Holotype: “Nr. 037” [white printed label], “ Holotype / Microbregma waldwico sp. nov. / des. Bukejs A. & Alekseev V.I.” [red printed label]; sex probably male. A complete specimen is embedded in a small, oval amber piece (length about 23 mm, width 13 mm, weight 0.9 grams) containing few cracks along the beetle body and large gas vesicles above elytra and basal half of pronotum. There are also three specimens of Nematocera (Diptera), two small specimens of Hymenoptera, numerous stellate hairs, few small pieces of organic material and small gas vesicles in the examined amber piece. The amber was not subjected to any fixation.

Type strata. Baltic amber, Upper Eocene, Prussian Formation.

Type locality. Baltic Sea coast, Yantarny village [formerly Palmnicken], Kaliningrad Region, Russia.

Etymology. The species name is a noun in apposition. Waldwico means “knight” in the Old Prussian language. The name refers to the habitus of the new species (like a knight in armor) and origin of the Baltic amber from the former area of the Old Prussian clans.

Diagnosis. Microbregma waldwico sp. nov. differs from the congeneric fossil species M. sucinoemarginatum ( Kuśka), 1992 and from the extant species M. emarginatum (Duftschmid), 1825 in its distinctly shorter ventrite 1, which is about 0.43 times the length of ventrite 2, and larger body size (5.1 mm). In M. sucinoemarginatum and M. emarginatum ventrite 1 is 0.63–0.71 times the length of ventrite 2, and body size is 3.5 mm in M. sucinoemarginatum and 3.4–4.5 mm in M. emarginatum ( Logvinovskij 1992; Terekhova & Drogvalenko 2011).

New species clearly differs from only other species of subfamily Anobiinae described from Baltic amber, Anobium jacquelinae Hawkeswood, Makhan et Turner, 2009 , based on proportions of abdominal ventrites and larger body size (3.0 mm in A. jacquelinae ).

Description. Body length 5.1 mm; body shape elongate cylindrical, strongly convex dorsally and moderately convex ventrally; unicolorous dark brown; covered with recumbent, fine, pale homogenous pubescence.

Head hypognathous, moderately convex, not visible from above; finely and densely granulated (central part of frons and vertex without granulation), with interspaces between granules covered with very fine and dense punctures. Compound eyes large, oval, convex, entire, with large, distinct facets; distance between eyes nearly equal to 1.8 times vertical diameter of one eye. Antennae 11-segmented, filiform; antennomeres 9–11 slightly longer (about 1.2 times longer) than antennomeres 1–8 combined; scape oval, weakly thickened; antennomere 2 subcylindrical, 0.83 times length of antennomere 1 and 0.45 times length of antennomere 11; antennomeres 3–8 small, subequal, antennomere 3 nearly 0.2 times length of antennomere 11; antennomeres 9–10 equal in length and similar in shape, distinctly dilated apically, with obliquely truncated apex; antennomere 11 spindle-shaped, 1.4 times longer than antennomere 10.

Pronotum transverse, apparently nearly as wide as base of elytra; anterior margin arcuate; lateral margins almost straight and sharp along the entire length; lateral sides explanate; in basal half with transverse ridge divided by impression in the middle, and with short, longitudinal ridge medially at the base; with wide impression near posterior angles (basal part of pronotum not clearly visible because of beetle’s location within amber piece and presence of large gas vesicles above it). Pronotal granulation dense and moderately large (larger than granules on head), distance between granules approximately equal to 0.1–1 times the diameter of each granule, granulation especially dense in basal half and near lateral sides.

Elytra nearly parallel, striate-punctate; humeral calli distinct; apex of each elytron separately rounded. Elytral punctures moderately small (in basal one-third distinctly larger than at apices), dense, arranged in regular striae; striae distinct throughout entire length of elytron; distance between strial punctures equal to 0.3–1 times diameter of one puncture; intervals strongly convex (especially in basal two-thirds of length), shagreened and covered with fine secondary punctation, distance between striae approximately 1.5–2.0 times diameter of one strial puncture. Pygidium completely covered by elytra.

Metathorax with fine and dense punctation; metasternum weakly convex posteriorly and flat in anterior half, without impressions; metepisternum about 5.5 times as long as wide, weakly widened anteriorly, anterior margin oblique, posterior margin straight, exterior lateral margin weakly sinuate.

Abdomen with five ventrites; abdominal sutures distinct at middle (i.e., ventrites are not fused); ventrites 1–4 with fine and sparse punctation, ventrite 5 with fine and dense granulation; anterior and posterior margins of all ventrites almost straight (except for widely rounded apex of ventrite 5). Ventrite 1 shorter, about 0.43 length of ventrite 2; ventrite 3 about 1.7 times length of ventrite 4; relative length ratios of ventrites 1–5 equal to 6:14:12:7:10.

Legs relatively long, distinctly projecting beyond lateral side of elytra; metafemora and metatibiae straight, nearly equal in length; metafemora 3.4 times as long as wide; metatibiae 6.2 times as long as wide. Metatarsi long, about 0.77 times length of metatibia; metatarsomeres 1–4 distinctly dilated apically; relative length ratios of metatarsomeres 1–5 equal to 6:5:5:4:5. Claws long, free and simple.

Note. Sex of specimen is determined on the basis of proportion of antennomeres: in males of recent Migrobregma antennomeres 9–11 are longer than the remaining part of the antenna.

Figures

FIGURES 1 – 2. Microbregma waldwico sp. nov., holotype. 1) dorsal view; 2) ventro-lateral view. Scale bar = 1 mm.

FIGURE 3. Microbregma waldwico sp. nov., holotype, ventro-lateral view, line drawing.