Ischalia (Eupleurida) dohnaturris, Bukejs, 2017

Bukejs, Andris, 2017, New fossil taxa of Ischalia Pascoe (Coleoptera: Ischaliidae) from Eocene Baltic amber, Zootaxa 4323 (2), pp. 229-238 : 230-233

Ischalia (Eupleurida) dohnaturris sp. nov.

( Figs 1–5 )

Type material. Holotype No. 5584-34 [KAM], adult, male. Complete beetle with partially exposed aedeagus and metathoracic wings, included in small elongate yellow amber piece with approximate dimensions: 18 × 11 × 9 mm. Venter of specimen partially obscured by “milky” amber opacity. Syninclusion represented by one stellate fagacean trichome.

Type strata. Baltic amber, mid-Eocene to Upper Eocene.

Type locality. Yantarny settlement (formerly Palmnicken ), Sambian (Samland) Peninsula, the Kaliningrad region, Russia.

Etymology. The specific epithet is used as a composite noun in genitive case and refers to the place of the holotype deposition. The epithet is formed after the German “der Dohnaturm” [Latin “turris” for German “der Turm” (the tower)]. Der Dohnaturm was built as the part of the fortification system of the former East Prussian capital Königsberg in 1853 and now accommodates the Kaliningrad Amber Museum.

Diagnosis. Absence of humeral elytral carinae suggests placement of species in subgenus Eupleurida (in contrast with subgenera Nitidischalia Young, 2011 and Ischalia s.str., which have humeral carinae reduced or fully developed). Macropterous metathoracic wings (completely lacking in all known extant Eupleurida species) is considered a plesiomorphic character state and not as a subgenerically diagnostic feature. Similarity of habitus between newly described species and Ischalia (Eupleurida) vancouverensis Harrington, 1892 from western North America provides additional support for placement within Ischalia (Eupleurida) .

Ischalia (Eupleurida) dohnaturris sp. nov. differs from extant species of subgenus in possessing following combination of characters: (1) macropterous metathoracic wings, (2) very short median longitudinal pronotal carina, (3) comparatively slender antennae with broadened terminal antennomere, (4) long and narrow elytra, (5) posterior pronotal angles not protruding, (6) apparently monochromatic elytra. This new species can be readily distinguished from other fossil Ischalia representatives by its narrow body, elytral carinae, pronotal structure, and long pubescence on elytral base.

Description. Body length 4.2 mm, body maximum width 1.4 mm; pronotum 0.75 mm long, maximum width 0.9 mm; elytral length 3.25 mm, maximal combined width of elytra (postmedially) 1.4 mm. Head, palpi, thorax, and abdomen appear to have originally been orange or light brown; elytra and antennae preserved with darker colour, almost black. Dorsal surface sparsely covered with short, fine and recumbent setae; elytral base with sparse, long (about 3–4× as long as puncture diameter), thin, recumbent pubescence. Head, pronotum, and elytra shiny, densely covered with large punctures (each about 3× as diameter of one eye facet); elytral punctures large, round, dense, separated by distance 0.25–0.30× of one puncture diameter in basal and periscutellar area, and by 0.5–1.0× in apical one-third.

Head transverse, slightly convex, constricted posteriorly. Compound eyes large, with vertical diameter about 4× transverse diameter; eye surface slightly convex, strongly emarginate on inner margin; glabrous with coarse facets. Antennae 11-segmented, filiform, moderately long, extending to basal one-fifth of elytra, antennomeres 3– 11 with fine pubescense, antennomere 11 flattened and dilated (widest). Relative length ratios of antennomeres 1– 11: 12-10-12- 12-12-12-12 - 12-12-10-15. Terminal maxillary palpomere bulbous and thickened, securiform with rounded angles; terminal labial palpomere triangular.

Pronotum slightly transverse, about 1.2× as wide as long, and distinctly narrower than elytral base; short median longitudinal carina present in posterior one-fifth of pronotal length, distinct as small triangular tubercle at posterior pronotal margin; with two wide, transverse, posterior impressions, and with widened longitudinal median impression in anterior half. Anterior pronotal margin rounded; lateral margins convex in anterior half and slightly concave posteriorly; basal margin slightly convex. Anterior pronotal angles broadly rounded; posterior angles nearly acute, slightly protruding. Scutellar shield large, triangular, almost as long as wide, impunctate.

Elytra subparallel-sided, narrow and long (2.3× as long as combined width); irregularly punctate; completely covering abdomen; base slightly concave; humeral calli well-developed. Elytra with sutural, lateral discal, and lateral carinae complete; humeral carina absent. Epipleura well-developed, reaching apex of elytra. Metathoracic wings fully developed.

Abdomen with five freely articulated, visible ventrites of subequal length. Apical part of aedegus visible ( Fig. 4 ).

Legs moderately long and slender. Femora and tibiae subequal in length. Tibial spurs absent. Tarsal formula 5- 5-4. All penultimate tarsomeres distinctly bilobate. Metathoracic tarsomere 1 slightly shorter than metathoracic tarsomeres 2–4 combined. Claws simple, acute, narrow, and symmetrical.

Note. Mesepisterna and mesosternal ventrite are not visible in examined specimen.

Figures

FIGURES 1 – 4. Ischalia (Eupleurida) dohnaturris sp. nov., holotype: 1 – habitus, dorsal view; 2 – habitus, ventro-lateral view; 3 – left antenna; 4 – apical part of aedegus. Not reproduced to the same scale.

FIGURE 5. Ischalia (Eupleurida) dohnaturris sp. nov., reconstruction, dorsal view. Scale bar = 1 mm.