Baltistena aurata, Batelka & Rosová & Prokop, 2023

Batelka, Jan, Rosová, Kateřina & Prokop, Jakub, 2023, Diversity and morphology of Eocene and Oligocene Mordellidae (Coleoptera), Acta Entomologica Musei Nationalis Pragae 63 (2), pp. 451-478 : 462

Baltistena aurata sp. nov.

( Figs 6D–G )

Type material. HOLOTYPE: PřfUK66, obtained from rmvveta (www. ambertreasure4u.com) (original number 224239532480): Baltic amber.

Description. Head subglobular, frons continuously convex, posterior edge of eye near posterior margin of head, elytra convex, metacoxae broad, comb formula 3//3/1/0/0, pygidium long. Main characters: Right antenna clearly visible, length ratios of antennomeres as follows: 1.25- 1.4-1->1->1-1.4-1.25-1.4-1.4-1.25-<2 (antennomeres IV and V only slightly longer than antennomere III), antennomeres I–X cylindrical, antennomere XI malleiform, widest in middle, all antennomeres distinctly longer than wide with ratio: 1.75-2-1.5-1.45-1.5-2-2.3-2.6-2.6-1.9-3.9. Maxillary palpomere II robust, almost as long as wide, palpomere III short, triangular, palpomere IV malleiform of Mordellochroa - type ( FRANCISCOLO 1957a: 216). Eyes roughly faceted. Eyes glabrous. Form of scutellum indiscernible. Form of basal side of pronotum indiscernible. Elytra 3.1× as long as pronotal disc. Form of protarsi: protarsomeres cylindrical, tarsomere I 6.25× as long as wide; tarsomere II 4× as long as wide; tarsomere III 3× as long as wide; tarsomere IV oblique at apex but without visible emargination; tarsomere V about 3× as long as wide. Structure of protibia indiscernible. Form of mesotarsomere IV: mesotarsomeres cylindrical, tarsomere I 5.6× as long as wide; tarsomere II 3.6× as long as wide; tarsomere III 3.5× as long as wide; tarsomere IV 2× as long as wide excised almost down to middle of its length; tarsomere V about 2.5× as long as wide. Mesotibia 1.5× as long as mesotarsal segments combined. Type of comb on metatibia: three distinct lateral combs of scale-like setae including preapical comb, combs do not reach middle of metatibia; preapical comb runs parallel with apical fringe of setae, remaining two combs oriented at different angles; few isolated patches of scale-like setae present behind proximal dorso-lateral comb. Metatibia with two spurs, outer spur shorter and sharply pointed. Metatarsomere I with row of spiniform setae consisting of about 20 short strong setae ventrally, metatarsomeres II–IV with row of spiniform setae consisting ventrally of about 17 short strong setae; metatarsomere I with three short lateral combs of scale-like setae; metatarsomere II with one short lateral comb of scale-like setae, metatarsomeres III–IV without combs; length ratio of metatarsal segments 1.75-1-1-1. Pygidium long and straight, 3.1× as long as hypopygium. Shape of metanepisternum: long and narrow, lower corner of posterior edge rounded, anterior edge 3× as long as posterior edge, ventral edge 5.5× as long as posterior edge. Metakatepisternum not discernible. Pretarsal claws long and straight, with 2–3 indistinct teeth on ventral edge. Tip of pygidium with distinct cluster of black scale-like setae. Lengths (in mm): pronotal disc = 0.54, elytra = 2.16, mesotibia = 0.8, metatarsomere I = 0.34, pygidium = 0.9. Etymology. The species name refers to the golden appearance of the body; adjective.

Differential diagnosis. Although the structure of mouthparts, shape of antennae, legs and pronotal disc, and overall habitus of Baltistena aurata sp. nov. appear familiar, this species cannot be placed in any extant genus of Mordellistenini because of the following characters: length over 4 mm; eyes glabrous; frons convex; terminal maxillary palpomere malleiform; antenna filiform, antennomeres cylindrical; antennomeres V–X 1.5–2.6× as long as wide; antennomere XI 1.6× as long as preceding one; anterior edge of pronotal disc rounded; pro- and mesotarsomere IV emarginated, shallowly bilobed; metatibial combs short; both metatibial spurs long, only slightly dissimilar. For its comparison with 37 extant genera and subgenera having pro- and mesotarsomere IV emarginated see Table 1.

Figures

Figs 6. A–G – Mordellistenini, Baltic amber.A–C – Baltistena ultima sp. nov., holotype, PřFUK65:A – habitus; B – antenna; C – hind leg and hypopygium. D–G – Baltistena aurata sp. nov., holotype, PřFUK66: D – habitus; E – hind leg; F – head frontally (maxillary palpomere IV marked by black arrow); G – hypopygium. Scale bars: A, D – 0.5 mm; C, E, F – 0.3 mm; B, G – 0.1 mm.