Xestipyge ikanti, Alekseev, 2016

Alekseev, Vitalii I., 2016, Description of two clown beetles (Coleoptera: Staphyliniformia: Hydrophiloidea: Histeridae) from Baltic amber (Cenozoic, Paleogene, Eocene), Baltic Journal of Coleopterology 16 (1), pp. 27-35 : 27-35

Xestipyge ikanti sp. nov.

( Figs. 4-8 )

Material examined. Holotype: No. 1470-6 [ CCHH]. A complete beetle is included in a small yellow amber piece embedded in a block of GTS-polyester resin with dimensions 12 x 7 x 3.5 mm. Syninclusions are absent. Ventral part and pygidium of the beetle is obscured by dense milky foam.

Type strata. Baltic Amber, Eocene.

Type locality. Yantarny settlement [Palmnicken], Sambian [Samland] peninsula, the Kaliningrad region, Russia .

Description.

Habitus. Total length (measured from the anterior margin of the pronotum to the posterior margin of the elytra) 1.5 mm, maximal body width 1.3 mm. Body oval, convex, shiny, smooth, finely punctured. Color blackish.

Head. Eyes present, lateral. Antennae geniculate, clubbed. Antennal club finely pubescent, without visible segmentation, with rounded apical margin. Frons concave (depressed medially), with symmetrical elevations above antennal cavities. Labral setation is not clearly discernible. Punctuation of the frons fine, sparse, separated by distance 2 x that of the puncture diameter.

Thorax. Pronotum transverse (length/width ratio 0.67), with sides convergent apically. Marginal stria complete laterally and present anteriorly, but obsolete in medial part of pronotum. Anterior pronotal margin almost straight; posterior margin arcuate. Anterior angles triangular, acute. Pronotal punctuation fine, comparatively dense, separated by distance 1-2 x that of the puncture diameter. Scutellum extremely small, triangular.

Alekseev V.I.

Wings. Elytra glabrous, shining, truncate, widest in anterior one-third, with seven complete striae: one marginal (subhumeral), five dorsal and one sutural. Dorsal stria 4 arched towards elytral suture and apparently connects with the united before sutural and dorsal stria 5. The basal interspace between discal striae 3 and 4 distinctly the widest ( Fig. 7 ). Elytral punctuation similar to that on the pronotum, fine and comparatively dense, becoming obsolete at elytral inclination in apical one-fourth, where it seems to be smooth. Sutural and discal striae 2-5 becoming shallow in apical part of elytron, with distinct longitudinal punctures visible. Hind wings are not apparent.

Legs. Femora flattened. Meso- and especially protibiae explanate, rounded in outline, with small teeth. Protibia with twelve weak and thin, gradually smaller outer marginal teeth. Protibial spur long, curved. Tarsal formula 5-5-5. All tarsomeres longer, than wide; tarsomere V the longest. Claws simple, acute and symmetrical.

Remark. The form of prosternal lobe, antennal cavities, details of venter and abdomen are not visible in the specimen. The generic placement is tentative at the moment, because many important characters are insufficiently visible in the studied inclusion. Further investigations by micro-computer tomography or finding of a ventrally visible specimen can help to make an indisputable systematical assignment.

Differential diagnosis. The specimen 1470-6 [ CCHH] may be placed in the recent genus Xestipyge Marseul based on the following characters: (1) dilated protibiae with small teeth and meso- and metatibiae distinctly slender; (2) characteristic position of the 4 and 5 dorsal and sutural striae on elytral base.

Resemblin g r ecen t species of Xesti pyge Marseul in body shape, sculpture, striae on elytra, and other visible characters, X. ikanti sp. nov. differs by the distinctly smaller body size (so the length of X. ornatum Reitter, 1888 compr ises 2.2-2.7 mm; th e len gth of X. puncticulatum Desbordes, 1919 is 1.8-2.6 mm; the length of X. simplex Vienna, 1993 is 2.0- 2.3 mm; the length of X. geminatum (LeConte, 1860) is 2.8-3.0 mm; the length of X. conjunctum (Say, 1825) comprises 2.2-2.5 mm) and by the distinctly depressed frons. The newly described species differs from the relatively close in size X. puncticulatum and X. simplex by the longer and distinct dorsal stria 5 connected with sutural stria, absence of the near sutural depression (present in X. puncticulatum ) and uniform punctuation of the dorsum. X. ornatum clearly differs by row of large punctures on the pronotal basis and finely rugose elytral apex; the North American species X. conjunctum and X. geminatum have the comparatively shorter dorsal stria 5 which is distinctly separated from sutural or dorsal stria 4.

Derivatio nominis: The epithet of this new species is devoted to the Prussian philosopher Immanuel Kant (22 April 1724 - 12 February 1804), who was born and lived in Königsberg, East Prussia. His contributions to metaphysics, epistemology, ethics, and aesthetics have had a profound impact on European philosophy.

Figures

Figure 7. Xestipyge ikanti sp. nov. Holotype; No. 1470-6 [CCHH]. Elytral striae basally (left side): subhumeral, 1-5 dorsal and sutural.

Figures 4-6. Xestipyge ikanti sp. nov. Holotype; No. 1470-6 [CCHH]. Habitus: 4 - Dorsal view; 5 - Ventral view; 6 - Dorso-frontal view.

Figure 8. Xestipyge ikanti sp. nov. Habitus dorsally, reconstruction.