Corticaria amberica, Reike, Hans-Peter, Bukejs, Andris, Arlt, Tobias, Kardjilov, Nikolay & Manke, Ingo, 2017

Reike, Hans-Peter, Bukejs, Andris, Arlt, Tobias, Kardjilov, Nikolay & Manke, Ingo, 2017, Phase-contrast synchrotron microtomography reveals the internal morphology of a new fossil species of the Corticaria-sylvicola - group (Coleoptera: Latridiidae), Zootaxa 4242 (3), pp. 578-590 : 581-587

Corticaria amberica sp. nov.

( Figs 1–9 , 12 )

Type material. Holotype: “017” [ACAB]; male. Complete beetle included in small and thin amber piece (length about 10 mm, width 8 mm, maximum thickness 2 mm) and preserved without supplementary fixation. Two cracks cross entire beetle (beetle is located along crack). Ventral side of head and pronotum are obscured by a “milky” opacity. Syninclusions are absent.

Paratypes: “005” [ACAB], “612” [GPIH], “8216” [GPIH], “8059” [HPR], “0024/2000” [WRUE], “0047/ 2001” [WRUE].

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

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

Etymology. The epithet of the new species is derived from the word “amber”.

Differential diagnosis. Shape of body and pronotum of new species, combined with denticulate pronotal lateral margins with each denticle bearing one seta apically, attributes Corticaria amberica sp. nov. to Corticaria sylvicola -group. Examination of genital features is necessarily needed for definitive determination of species within this group.

In genital structure, Corticaria amberica sp. nov. ( Figs 5 , 12 ) is close to the extant species C. pinicola C.N.F. Brisout de Barneville, 1866 ( Fig. 10 ) and C. abdominalis Dajoz, 1970 ( Fig. 11 ):

- C. pinicola has some tooth-shaped sclerites of endophallus inside aedeagus (as in the new species) but differs from the new species in shape of median lobe of aedeagus;

- C. abdominalis has shape of aedeagus similar to C. amberica sp. nov., but differs from the new species in shape and larger size of tooth-shaped sclerites of endophallus inside aedeagus.

Corticaria amberica sp. nov. differs significantly from all described extinct species of Corticaria in shape of habitus and also pronotum.

Description. Holotype. Body length 1.6 mm, maximum width 0.76 mm; body shape elongate, convex dorsally and moderately convex ventrally; body colour dark brown; head and elytra with short, dark, semi-erect setae directed posteriad, pronotum appears glabrous.

Head transverse, evenly convex dorsally; covered with dense and moderately large punctures that are markedly larger than diameter of one compound eye facet, interspaces between punctures smooth and distinctly less than one puncture diameter in width. Compound eyes large, convex with moderately large and distinct facets; distance between eyes nearly equal to 3× transverse diameter of compound eye. Tempora absent. Anterior part of head and mouthparts not clearly visible because of milky amber cover. Antennal insertions located slightly before anterior edge of eyes. Antennae 11-segmented, 0.54 mm long. Scape cylindrical, not distinctly visible, larger than antennomere 2; antennomere 2 wider than antennomere 3, and as long as antennomere 3; antennomere 3 is 1.75× as long as antennomere 4; antennomere 4 shorter than antennomere 5; antennomeres 3–8 longer than wide (1.9–4.0×) and widened apically. Antennal club loose, distinctly 3-segmented; antennomere 11 widely suboval and acute apically; antennomeres 9–10 subequal in size, as long as wide, and about 0.5× as long as antennomere 11.

Pronotum 0.31 mm long and 0.5 mm wide, broadly rounded, transverse, approximately 1.7× as wide as long; outline slightly narrowed anterad and more so posterad, widest in middle; with oval impression at base and weak impressions near each posterior angle; covered with dense and moderately large punctures (similar to punctures on head), distance between punctures smaller than diameter of puncture, interspaces slightly shagreened. Lateral margins widely rounded and denticulate (with 8 teeth on each side; each denticle bearing seta apically); anterior margin almost straight in dorsal view; posterior margin completely bordered. Pronotal disc convex, with moderately to steep-sloping sides.

Scutellar shield transverse, shagreened, impunctate. Elytra 1.13 mm long and 0.76 mm wide, about 1.48× as long as wide combined, oval, convex, widest in middle, shiny. Base of elytra distinctly wider than pronotal base. Humeral calli developed. Elytral punctures large and dense, becoming smaller in posterior half; in basal one-third of elytral length, punctures larger than punctures on pronotum; arranged in regular striae, with striae distinct throughout entire length of elytra; distance between punctures in striae equal to 1.0× diameter of puncture; interstriae flat, covered with fine, irregular secondary punctation, distance between striae approximately 2× diameter of one strial puncture (narrower at base of interstriae). Number of striae not countable.

Prosternum, meso- and metaventrites covered with large punctures (as in pronotal punctures), distance between punctures equal to 1.0× diameter of puncture; shagreened. Pro- and mesocoxae nearly globose, narrowly separated (distance between them less than transverse diameter of metacoxa); metacoxae elongate, transverse, about 2.5× as wide as long, with distance between them about 1.4× transverse diameter of mesocoxa. Metepisternum narrow, with nearly straight lateral margins, about 6.5× as long as wide. Metaventrite with trisinuated basal margin.

Abdomen with five visible ventrites; shagreened; ventrite 1 longest, with sparse and moderately large punctures (as metaventral punctures); ventrites 2–5 covered with distinctly smaller and sparser punctures. Relative length ratios of ventrites 1–5 equal to 14-4-4-3-6.

Legs moderately long and narrow. Trochanters slightly elongate. Femora spindle-shaped, thickest at middle and about 2× as wide as tibiae. Tibiae slender, with tibiae and femora approximately comparable in length. Tarsi with three simple subcylindrical tarsomeres. Tibiae about 1.4× as long as tarsi; tarsomeres 1 and 2 subequal in length; ventral process of pro- and mesotarsomere 1 reaches middle of tarsomere 2; metatarsomere 3 about 1.5× longer than metatarsomeres 1–2 combined. Claws simple, small and thin.

Aedeagus 0.68 mm long and 0.05 mm wide ( Figs 5 , 12 ), with some difficult to discern tooth-shaped sclerites of endophallus; in size and shape, endophallus sclerites similar to sclerites in recent species C. pinicola ( Fig. 10 ). Aedeagus shape of new species resembles that of C. abdominalis ( Fig. 11 ), but aedeagus is smaller and toothshaped sclerites of endophallus are smaller and differ in shape.

Paratypes. Body length: “005”— 1.55 mm, “612”— 1.4 mm, “8216”— 1.43 mm, “8059”— 1.6 mm, “0024/ 2000”— 1.5 mm, “0047/2001”— 1.49 mm; otherwise, all paratypes are similar in all visible morphological characters to holotype.

Figures

FIGURES 1 – 2. Corticaria amberica sp. nov., holotype “ 017 ” [ACAB]: 1 — habitus, dorsal view; 2 — habitus, ventral view.

FIGURES 3 – 5. Corticaria amberica sp. nov., holotype “ 017 ” [ACAB], phase-contrast synchrotron microtomography renderings (BESSY II, Helmholtz-Zentrum, Berlin): 3 — habitus, dorsal, ventral and lateral views; 4 — location of aedeagus inside abdomen; 5 — aedeagus, lateral and ventral views.

FIGURES 6 – 9. Corticaria amberica sp. nov., paratypes: 6 — habitus, dorsal view, paratype “ 0024 / 2000 ” [WRUE]; 7 — habitus, dorso-frontal view, paratype “ 612 ” [GPIH]; 8 — habitus, ventral view, paratype “ 8216 ” [GPIH]; 9 — habitus, dorsal view, paratype “ 8059 ” [HPR].

FIGURES 10 – 12. Aedeagus: 10 — Corticaria pinicola, ventral view (drawing by W. H. Rücker); 11 — C. abdominalis, ventral view (drawing by W. H. Rücker); 12 — C. amberica sp. nov., lateral and ventral views, reconstruction.