Archaeonebria Kavanaugh & Schmidt, 2019

Schmidt, Joachim, Scholz, Stefan & Kavanaugh, David H., 2019, Unexpected findings in the Eocene Baltic amber forests: Ground beetle fossils of the tribe Nebriini (Coleoptera: Carabidae), Zootaxa 4701 (4), pp. 350-370 : 351-353

Archaeonebria Kavanaugh & Schmidt , gen. n.

Type species. Archaeonebria inexspectata Schmidt & Kavanaugh , gen. n., sp. n., fossil species from the Eocene Baltic amber.

Description. Body length: Rather small with respect to average in nebriine beetles, standardized body length 6.4–7.2 mm.

Head: Broad and short. Mandibles short ( Figs 31–33 ), with scrobal seta present. Labrum with apical margin very slightly concave (as shown by the negative imprint of the labral margin in Fig. 31 ), with a row of six setae near apical margin. Clypeus with one pair of setae in normal position for Nebriini . Head with one supraorbital seta each side in normal position for Nebriini . Eyes large, moderately protruded laterally. Frons and vertex smooth, without punctures, frontal impressions very shallow, indistinct ( Fig. 31 ). Antennae rather short, with 10 th antennomere extended to the pronotal base; scape moderately robust, moderately narrowed towards base ( Figs 31, 32 ); antennomeres 2–11 rather slender ( Figs 8 , 15, 17 ); antennal pilosity beginning from the 5 th antennomere, with basal four antennomeres completely smooth apart from the apical circle of primary setae ( Fig. 17 ). Palpomeres rather short, penultimate labial palpomere with three setae ( Fig. 28 ), without posteroapical seta, terminal labial palpomere slightly longer than penultimate one. Ligula short, ventrally keel-like elevated, with apex slightly pointed, slightly protruded ventrally, completely fused with paraglossae, latter not protruded apically ( Figs 34–36 ). Mentum with median tooth bifid, with internal incision moderately deep, and with three pairs of setae ( Fig. 32 ): one pair each near apices of mentum tooth, posteriad of mentum tooth, and near laterobasal edges of mentum. Submentum with four pairs of setae ( Fig. 32 ).

Prothorax: Pronotum ( Figs 37–39 ) large and transverse, broadest in middle, with lateral margin only slightly narrowed towards base and with basal margin distinctly broader than apical margin. Apical margin slightly convex in middle, markedly shifted anteriad towards apical angles; latter large, rectangular or slightly acute. Basal margin very slightly convex or straight in middle, slightly sinusoidal towards sides, with laterobasal angles almost rectangular, slightly projected posteriad, at their extreme apices very slightly protruded laterally as very small, blunt teeth. Lateral margin more markedly arcuate in apical half, almost straight before base. Lateral gutter wide throughout, markedly widened towards the laterobasal depressions; latter large, markedly deepened in middle. Basal transverse depression distinct; median longitudinal impressions deep, obsolete near apex and base. Disc, lateral gutter and basal depressions smooth, without conspicuous punctures. Both lateral and laterobasal setae present, with lateral seta situated within lateral gutter slightly before pronotal middle, and laterobasal seta situated near base, distanced from the lateral margin by the width or the half diameter of the setiferous pore. Prosternum at its sides, and proepisternum densely punctate; prosternal process with marginal bead complete ( Fig. 27 ).

Pterothorax: Elytra moderately short, in dorsal view broad-ovate, slightly or moderately broader than pronotum; disc moderately convex in middle, distinctly flattened near base ( Fig. 40 ). Humerus broad, distinctly wrinkled ( Fig. 41 ). Elytral apices shortly rounded. Elytral basal bead almost complete, absent between bases of parascutellar stria and first stria ( Fig. 41 ); basal and marginal bead forming a slightly obtuse angle. Parascutellar stria long, deeply punctured, not connected with the first stria; striae 1–7 very slightly impressed, even on disc, distinctly punctured throughout ( Fig. 41 ); all intervals completely flat. Parascutellar seta present, situated in the interval between basal portions of parascutellar stria and first stria; third interval with three discal setae, all situated close to the third stria, with first seta situated at the posterior end of anterior elytral fifth, second slightly anteriad middle, and third slightly anteriad apical quarter; elytral praeapical seta present, situated about at middle of the third interval near apices of the second and third striae ( Fig. 41 ); elytral umbilicate series comprised of 9–10 setae ( Fig. 40 ). Metepisternum with lateral margin about 1.2–1.3 times as long as apical margin. Hind wings fully developed ( Figs 7, 8 ).

Legs: Rather short and robust, with metafemora markedly thickened in middle ( Fig. 30 ). Metacoxa with one anterior and one posterior seta, metatrochanter asetose ( Fig. 10 ), metafemur in distal half with two short setae on dorsoapical surface, glabrous on ventral surface ( Fig. 30 ). Mesotibia with distinct dorsal groove extended over most of its length. All tarsomeres glabrous on dorsal surface ( Fig. 29 ); protarsomeres 1–3 broadened in males, slender in females; fourth metatarsomere with ventroapical margin trunctate; fifth pro- and mesotarsomeres with three, fifth metatarsomere with four pairs of strong setae on ventral surface ( Fig. 29 ).

Abdomen: Sternites IV–VI each with a single pair of setae near apical margin; sternite VII in males paramedially with one, in females with two pairs of setae ( Fig. 30 ).

Female genitalia ( Figs 50–53 ): Apical gonocoxite short, slender in ventral aspect but broad and broadly rounded apically in lateral aspect; basal gonocoxite longer and slightly wider, fused with the apical gonocoxite medially but broadly separated and membraneous laterally; basal gonocoxite with three or four stout spiniform setae arranged in a ventral diagonal row from medioapical to laterobasal; dorsomedial edge of fused apical and basal gonocoxites with two stout spiniform setae. Female genital tract could not be imaged.

Male genitalia ( Figs 42–49 ): Aedeagal median lobe moderately long, markedly bent throughout, tube-like, moderately robust, slightly widened in apical half, somewhat twisted counterclockwise; median lobe base closed; apical ostium about 2/3 of length of median lobe; basal bulb moderately large, with a well-developed sagittal aileron; apical lamella moderately long, tongue-shaped, slightly bent to the right. Parameres asymmetrical, with left one moderately large, broad and flat, without obvious apical apophysis, and with right one longer and slenderer, with a slightly bent lanceolate apical apophysis.

Figures

FIGURES 31–36. Archaeonebria inexspectata gen. n., sp. n., volume rendering of the holotype (Figs 31, 32, 34) and paratype #2 (Fig. 33, 35, 36). Fig. 31, head, dorsal aspect; the arrows point to the insertions of the labral setae, clypeal seta, and supraorbital seta. Remark: Note the deformation of the labral apical margin with respect to its negative imprint on the inclusion wall, which represents its original state. Fig. 32, head, ventral aspect; the arrows point to the insertions of the setae on mentum and submentum. Figs 33, 34, mouthparts, apicoventral aspect of different specimens using different greyscale thresholds. Figs 35, 36, separated images of the ligula with the completely fused paraglossae (Fig. 35, ventral aspect; Fig. 36, apicoventral aspect). Abbreviations: ant = antenna; dp = dust particles; la = lacinia; lig = ligula; lig-a = apex of ligula; lp-l = left labial palpus; lp-r = right labial palpus; m = mentum; md-l = left mandible; md-r = right mandible; mp-l = left maxillary palpus; mp-r = right maxillary palpus; mx = maxilla; n = negative imprint of the labral margin; p = shrunken remains of the labral margin; pgl = paraglossa.

FIGURES 7–10. Archaeonebria inexspectata gen. n., sp. n., light microscopic images of the paratype #1. Fig. 7, dorsal aspect of the embedded specimen. Fig. 8, ventral aspect. Fig. 9, general view with contours of the amber piece, showing several embedded insects (see text for details); the arrow points to the position of the embedded Archaeonebria specimen. Fig. 10, basal part of the left hindleg; the arrows point to the positions of the anterior and posterior metacoxal setae. Abbreviations: mcx = metacoxa; mtr = metatrochanter; w-l = left hindwing; w-r = right hindwing.

FIGURES 14–17. Archaeonebria inexspectata gen. n., sp. n., light microscopic images of the paratype #2. Fig. 14, dorsal aspect of the embedded specimen. Fig. 15, right lateral aspect. Fig. 16, general view with contours of the amber piece. Fig. 17, right antennomeres II–VI.

FIGURES 27–30. Archaeonebria inexspectata gen. n., sp. n., light microscopic images of paratypes #1 (Figs 27, 28, 30) and #2 (Fig. 29). Fig. 27, prothorax and part of the head, ventral aspect. Fig. 28, left labial palpus; the arrows point to the three setae inserted on the penultimate palpomere. Fig. 29, left metatarsomeres II–V. Fig. 30, abdomen and left metafemur, ventral view; the arrows point to the insertions of the two dorsoapical setae of the femur, the setae near apical margins of the sternites IV and V (if visible; the setae on sternite VI are shadowed by the right metatibia), and the two pairs of setae on sternite VII. Abbreviations: ce = compound eye; gu = gula; lp-2, 3 = labial palpomeres 2, 3; m = mentum; mf = metafemur; pcx = procoxa; pep = proepisternum; pst = prosternum; st-IV–VII = abdominal sternites IV–VII.

FIGURES 37–41. Archaeonebria inexspectata gen. n., sp. n., volume rendering. Fig. 37, pronotum of the holotype. Fig. 38, pronotum of the paratype #1. Fig. 39, pronotum of the paratype #2; the arrows point to the lateral seta (pls) and basolateral seta (pbs). Figs 40, 41, right elytron of the holotype (Fig. 40, lateral aspect, Fig. 41, dorsal aspect); the arrows point to the insertions of the parascutellar seta (pss), discal setae (ds1–3), praeapical seta (pas), and to the setae of the umbilicate series (us1–9).

FIGURES 42–53. Archaeonebria inexspectata gen. n., sp. n., volume rendering of the aedeagus of the holotype using different grey scale thresholds (Figs 42–49), and of the female ovipositor of paratype #2 (Figs 50–53; the ovipositor was separated by the segmentation function of Amira software in Figs 51–53). Figs 42, 45, left lateral view. Figs 43, 46, view slightly diagonal from behind, frontally to the apical lamella. Figs 44, 47, right lateral view. Fig. 48, frontal view towards median lobe base. Fig. 49, view from posterad towards median lobe apex. Fig. 50, section of the female abdomen in ventral view. Fig. 51, ovipositor in ventral view. Fig. 52, postero-left lateroventral view. Fig. 53, dorsal view.Abbreviations: al = apical lamella of aedeagal median lobe; ap = lanceolate apophysis of left paramere; ds = dorsal row of spiniform setae on the edge of the fused apical and basal gonocoxites; g = gut; gc 1 = basal gonocoxite; gc 2 = apical gonocoxite; ltg = laterotergite; mtg = mediotergite; o-a = extreme apex of apical ostium of median lobe; o-b = extreme base of apical ostium; pm-l = left paramere; pm-r = right paramere; se = sagittal aileron; sp = sensory pit; vs = ventral row of spiniform setae (only shown on right basal gonocoxite);?vs = the pore marks the insertion of a probable additional spiniform seta of the ventral series.