Limnoxenus olenus, Fikáček & Prokop & Nel & Umr, 2010

Fikáček, Martin, Prokop, Jakub, Nel, André & Umr, Cnrs, 2010, Fossil water scavenger beetles of the subtribe Hydrobiusina (Coleoptera: Hydrophilidae) from the Late Oligocene locality of Aix-en-Provence (France), Acta Entomologica Musei Nationalis Pragae 50 (2), pp. 445-458 : 448

Limnoxenus olenus sp. nov.

( Figs. 1–6 )

Type locality and horizon. Aix-en-Provence (43°19′N 5°27′E), Bouches-du-Rhône , France ; Aix-en-Provence Formation, Latest Oligocene, Late Chattian, about 22.5 million years ago.

Type material. HOLOTYPE: MNHN A32835 (part and counterpart; nearly completely preserved beetle in ventral view with preserved maxillary palpi and fore and hind legs) . PARATYPE: MNHN A32836 (part and counterpart; nearly completely preserved beetle in ventral view with partly preserved legs) ; both deposited in Laboratoire de Paléontologie , Muséum national d’Histoire naturelle, Paris, France .

Description. Body elongate oval. For body measurements, see Table 1.

Head. Dorsal surface of head with visible frontoclypeal sutures arising very close to anterior margin of eyes; anterior margin of clypeus weakly emarginate. Eyes large, not protruding laterad of head outline, interocular distance 2.5 times the width of one eye in dorsal view. Gula weakly narrowing anteriad, bearing distinct median longitudinal ridge posteriorly; genae with coarse granulate sculpture. Maxillary bases connected by sharp transverse ridge. Mentum transverse, 1.8 times as wide as long, anterior margin arcuately convex. Maxillary palpus slender, shorter than width of head; maxillary palpomere 2 longest, slightly bent inwards; palpomere 4 longer than palpomere 3.

Thorax. Pronotum weakly narrowing anteriad, posterior corners rounded. Prosternum carinate medially; procoxal cavities contiguous medially; mesal portions of notopleural suture open. Transverse ridge below posterior margin of prothorax well developed, nearly reaching lateral margin. Mesoventrite divided from mesanepisternum by well developed anapleural sutures, shape of mesoventrite subtriangular with concave lateral margins (‘trapezoidal’ sensu SHORT & LIEBHERR (2007: Figs. 5A–C )); mesoventrite with high longitudinal median keel, anteromedian pit of mesoventrite (‘mesoventrite depression’ sensu SHORT & LIEBHERR (2007)) well developed. Scutellar shield large, triangular, ca. as long as wide. Elytra with sharply impressed sutural stria and nine longitudinal punctural series, series 7–10 (i.e., four lateral-most series) probably sharply impressed at least in posterior half. Mesocoxal cavities transverse, contiguous medially. Metaventrite slightly longer than mesoventrite; median portion longitudinally elevate, with sharp submedian arcuate ridges delimiting the median portion (both median elevation and submedian keels not seen in the paratype). Metanepisternum 3.2 times as long as wide, nearly equally wide throughout, with sharp transverse ridge anteriorly.

Figures

Figs. 1–2.Limnoxenus olenus sp. nov., holotype (1 – part, 2 – counterpart). Abbreviations: aps – anapleural suture; aes3 – anepisternum 3; cxc2 – mesocoxal cavities; fcs – frontoclypeal suture; guls – gular suture; mxp4 – maxillary palpomere 4; msd – mesoventrite depression; msv – mesoventrite; mt – mentum; mtv – metaventrite; prc – prosternal carina; sc – scutellar shield; sstr – elytral sutural stria; tf – transverse fold of prothorax.

Figs. 3–6. Limnoxenus olenus sp. nov. 3–4 – holotype (3 – part, 4 – counterpart); 5–6 – paratype (5 – part, 6 – counterpart).