Ischalia youngi, Alekseev, Vitalii I. & Telnov, Dmitry, 2016

Alekseev, Vitalii I. & Telnov, Dmitry, 2016, First fossil record of Ischaliidae Blair, 1920 (Coleoptera) from Eocene Baltic amber, Zootaxa 4109 (5), pp. 595-599 : 595-598

Ischalia youngi sp. nov.

( Figs.1–4 ).

Material examined. Holotype No. 1684-1 [ CCHH], adult male (with partly exposed apex of male aedeagus). Beetle

inclusion in a small amber piece embedded in a block of GTS-polyester resin with dimensions 11 x 11 x 8 mm.

Syninclusions are represented by three fagacean stellate hairs. Type strata. Baltic Amber, Upper Eocene, Prussian Formation (Priabonian). Estimated age: 37.2–33.9 Ma. Type locality. Yantarny settlement (formerly Palmnicken), Sambian (Samland) Peninsula, Kaliningrad region, W

Russia.

Differential diagnosis. Ischalia youngi sp. nov. is herewith assigned to the nominate subgenus based on the following characters: (1) humeral elytral carinae well-developed; (2) metathoracic wings fully developed; (3) mesepisterna widely separated by mesosternum; (4) prebasal pronotal depressions well-developed. The newly described Eocene species is compared with recent congeners and distinguished by the combination of the following characters: median longitudinal pronotal carina present in basal half; posterior angles of pronotum not or vaguely protruding; pronotum comparatively narrow; humeral carinae about 1/4–1/5 of elytral length.

Description. Total body length 5.7 mm, body width 2.5 mm, pronotum 0.7 mm long, maximum width 1.1 mm, elytral length 4.5 mm, maximal combined width postmedium of elytra 2.5 mm. Body entirely black, sparsely covered with short, fine and decumbent setae. The monochrome body colour of the holotype specimen may be result of the fossilization in amber.

Head: Eyes not strongly protruding from lateral outline of the head, slightly emarginate to accommodate antennal insertions, lacking intrafacetal setae, almost covering whole tempora. Antennae filiform, long and robust, densely and shortly pubescent, reaching basal third of elytra; antennomeres 1 and 3 are the longest; antennomere length ratios: 26-20- 20-20-20-20-20-20-17-15-21. Terminal antennomere tapered, pointed. Terminal maxillary palpomere strongly securiform, terminal labial palpomere triangular.

Thorax: Dorsal punctures of pronotum very sparse and fine, surface almost impunctate; pronotum with lateral and basal collar, almost as wide as one elytron; dorso-mesal surface strongly gibbose anteriorly, sloping downwardly in posterior two-thirds, thence gradually upward toward posterior margin. Median longitudinal pronotal carina distinct and prominent in basal half, with two transverse sublateral impressions before the base, separated by the median carina. Anterior margin of pronotum shallowly emarginated mesally. Lateral pronotal margins evenly arcuate. Basal pronotal angles almost truncate; posterior angles not or very vaguely protruding; anterior angles broadly rounded.

Mesosternum rounded apically. Mesepisterna separated by the mesosternum by distance ~ 0.25 mm. Scutellum large, triangular, with longitudinal, oval apical elevation. Elytra with sutural, humeral, lateral discal, and lateral carinae well developed; elytra elongate, almost completely covering abdominal ventrites, sub-parallel, with broadly rounded humeri. Dorsal surface of elytra densely, coarsely, and irregularly punctate. Sutural and lateral carinae complete; each lateral discal carina gradually curving obliquely toward the sutural carina but becoming obsolete and not fusing with it; humeral carinae shorter than one-fourth the length of elytra. Metathoracic wings fully developed, partially exposed in the holotype specimen.

Abdomen: With five freely articulated, visible ventrites of subequal length; the last visible abdominal ventrite almost truncate apically, with distal parts of male aedeagus partially exposed.

Legs: All coxae transverse. Prothoracic coxae contiguous; mesothoracic and metathoracic coxae very narrowly separated. All trochanters visible and well-developed. Femora and tibiae slender. Tibial spurs absent. Tarsi 5-5-4. All penultimate tarsomeres distinctly bilobate. Basal metathoracic tarsomere as long as combined length of three remaining tarsomeres. Claws simple, acute, narrow, and symmetrical.

Etymology. Patronymic. This species is named after our colleague Dr. Daniel K. Young, University of Wisconsin, Madison, Wisconsin, U.S. A, in honor of his valuable contributions to the study of Ischaliidae .

Figures

FIGURES 1 – 3. Ischalia youngi sp. nov., holotype male, habitus. 1) dorsal view; 2) ventral view; 3) lateral view.

FIGURE 4. Ischalia youngi sp. nov., reconstruction of the external shape, dorsal view.