Baltistena ultima, 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 : 459-462

Baltistena ultima sp. nov.

( Figs 6A–C )

Type material. HOLOTYPE: PřfUK65, obtained from rmvveta (www. ambertreasure4u.com) (original number 274532540629): Baltic amber.

Description. Head subglobular, frons continuously convex, posterior edge of eye near posterior margin of head, elytra convex, metacoxa expanded, comb formula 4//3/3/0/0, pygidium long. Main characters: Form of antennae: only 10 distal antennomeres visible, length ratios as follows:?-1.6-1-1.2-1.6-1.2-1.4-1.4-1.4-1.4-2.2 (i.e., antennomere III probably shortest), antennomere XI longest, notched (emarginated) laterally at apex, thus distal half of antennomere half as wide as basal half. Structure of maxillary palpi indiscernible. Size of eye facets indiscernible. Presence or absence of interfacetal setae uncertain. Form of scutellum indiscernible. Basal side of pronotum indiscernible. Elytra 3.1× as long as pronotal disc. Form of protarsi: protarsomere I cylindrical, 7× as long as wide; protarsomere II cylindrical, 4× as long as wide; protarsomere III subcylindrical, 2× as long as wide at apex; protarsomere IV as long as wide, dilated at apex; protarsomere V elliptical, about as long as protarsomere III. Protibia very narrow, slightly curved, distinctly longer than protarsus. Form of mesotarsomere IV indiscernible. Mesotibia 1.1× as long as respective tarsus. Metatibia with at least four dorso-lateral combs of scale-like setae including preapical one. Metatibia with two long, very thin and sharply pointed spurs. Metatarsomere I with row of spiniform setae consisting of ca 15 short strong setae ventrally and with five combs of lateral scale-like setae, the first three of them with only a few setae; metatarsomere II with row of spiniform setae consisting of ca. 15 short strong setae ventrally, and with two short lateral combs of scale-like setae; metatarsomeres III and IV with row of spiniform setae consisting of ca. 15 short strong setae ventrally, lateral combs of scale-like setae absent. Pygidium 2.3× as long as hypopygium, distinctly bowed ventrally. Shape of metanepisternum indiscernible. Absence or presence and shape of metakatepisternum (newly added). Pretarsal claws long and straight, bidentate at apex. Tip of pygidium with distinct cluster of black scale-like setae.

Lengths (in mm): pronotal disc = 0.5, elytra = 1.8, metatarsomere I = 0.4, pygidium = 0.9.

Etymology. The species name refers to the specific modification of antennomere XI; adjective.

Differential diagnosis. Baltistena ultima sp. nov. can be readily separated from other members of the family by the presence of dorso-lateral combs of scale-like setae (= ‘ridges’) including a preapical one on the metatibia and metatarsomeres (character of Mordellistenini ), antennomere XI laterally notched at apex, and protarsomere IV emarginated at apex. Apically notched antennomere XI occur only in a few taxa of Mordellidae . In Mordellistenini this character is present only in Mordellistena (Mordellokoiles) grandii Franciscolo, 1942 – a monotypic subgenus from southern Italy ( FRANCISCOLO 1942), and in Mordellini only in the species of Tomoxia (e.g., LILJEBLAD 1945: Plate III, fig. 16a; FRANCISCOLO 1957a: Fig. 5.5 ). The genus Mordellistena differs from Baltistena ultima sp. nov. in having cylindrical protarsomeres with a truncate (= straight cut) apex. The above-mentioned species are unlikely to be related as this peculiar modification of antennomere XI apparently appeared in both tribes independently. The function is unknown.

Figures

Figs 5. A–J – Mordellistenini, Baltic amber. A–E – Baltistena soror (Ermisch, 1941), type: A – habitus. B – middle leg. C – posterior pronotal margin. D, E – head and thorax. F–J – Baltistena sergeli (Ermisch, 1943), holotype: F – habitus; G, H – hind legs; I – maxillary palpomeres IV (black arrows); J – protarsus. Scale bars: A, F, I – 0.5 mm, B – 0.05 mm; C, J – 0.2 mm; D, E, G, H – 0.3 mm.

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.