Baltistena nigrispinata Batelka, Troeger & Bock, 2024

Boudinot, Brendon E., Bock, Bernhard L., Weingardt, Michael, Troeger, Daniel, Batelka, Jan, LI, Di, Richter, Adrian, Pohl, Hans, Moosdorf, Olivia T. D., Jandausch, Kenny, Hammel, Joerg U. & Beutel, Rolf G., 2024, Et latet et lucet: Discoveries from the Phyletisches Museum amber and copal collection in Jena, Germany, Deutsche Entomologische Zeitschrift 71 (1), pp. 111-176 : 111

† Baltistena nigrispinata Batelka, Troeger & Bock sp. nov.

Etymology.

The species name nigrispinata refers to distinctly black combs on metatibia and tarsomeres contrasting with orange surface of the cuticle.

Type materials.

Holotype. PMJ Pa 5870, Baltic amber. Sex indeterminable. Cybertype: Appendix 1: Fig. A6 .

Paratypes. None.

Differential diagnosis.

The species belong to the subgroup of Mordellistenini with emarginated or dilated penultimate pro- and mesotarsomere sensu ( Ermisch 1950). To this possible clade belong twelve of fourteen of Baltic Mordellistenini so far described ( Batelka et al. 2023). In † B. nigrispinata sp. nov. the eyes are glabrous without interfacetal (= interommatidial) setae as in † Palaeostena eocenica Kubisz from which it differs by lower number of combs on metatibia and metatarsomeres I and II, and by the shape of palpomere IV which is type C1 sensu Franciscolo (1957) in † Palaeostena . The ultimate maxillary palpomere is securiform as in † Baltistena korschefskyi (Ermisch) from which † B. nigrispinata sp. nov. differs by the absence of combs on metatarsomere III and by the comb formula. The ring of short black scale-like setae on the tip of pygidium is similar to that in † Baltistena brevispina Batelka, Rosová & Prokop and in † Palaeostena eocenica . The metakatepisternum is fused early with the metaventrite in the middle of its posterior edge, which has so far only been observed in † Palaeostena eocenica among the Eocene Mordellistenini , while the other four species described by Batelka et al. (2023) have a separate and discernible metakatepisternum that is elongate and extends to the metanepisternum. Based on the shape of the body, the glabrous eyes, the shape of the metakatepisternum, and the setae on the cauda, † B. nigrispinata sp. nov. most closely resembles † Palaeostena eocenica . Also, while adding the species into the key provided by Batelka et al. (2023) it is coupled with † Palaeostena eocenica and † Baltistena amplicollis (Ermisch). From the last species, † B. nigrispinata sp. nov. differs by the comb formula, the shape of the ultimate maxillary palpomere, and the length of antennomeres III and IV, combined compared to antennomere V.

This set of characters observed for † B. nigrispinata sp. nov. supports the hypothesis that the species of Baltic Eocene Mordellidae formed a characteristic fauna that was much different from extant European representatives ( Batelka et al. 2023).

Description.

Head subglobular, frons continuously convex, hind margin of eye at posterior margin of head, elytra convex, pygidium long, metacoxa broad, comb formula 3//2/1/0/0. Habitus in lateral view (Fig. 23A , Fig. 24A ).

Main diagnostic characters as defined by Franciscolo (1967) and Batelka et al. (2023): Right antenna well visible, left antenna (Fig. 23B ) visible from basal part of antennomere II, antennomeres subcylindrical, slightly compressed, without any lateral projections, antennomeres III-IV slightly widening towards apex (Fig. 24B ), length ratios of antennomeres as follows:?-1.4-1.0-1.25-1.6-1.4-?-?-?-1.6-2.0; antennomere XI regularly rounded at apex; antennae densely covered by erect or semierect sensilla from antennomere III. Maxillary palpomere I small, palpomere II prolonged, widest at apex, palpomere III short, triangular, palpomere IV long, securiform of Mordella -type ( Franciscolo 1957: fig. 6_A1) (Fig. 24C ). Eyes finely faceted; Eyes glabrous without interfacetal setae. Scutellar shield continuously rounded ( Franciscolo 1957: fig. 9_type10) (Fig. 24D ). Basal side of pronotal disc widely convex in central part (Fig. 24E ). Elytra 3.2 × as long as pronotal disc. Form of protarsi indiscernible. Structure of protibia indiscernible. Mesotarsomeres I - III cylindrical, tarsomere I 6.1 × as long as wide; tarsomeres II and III 5.0 × as long as wide; tarsomere IV excised almost to middle region; tarsomere V about 3.0 × as long as wide. Mesotibia very slightly shorter than metatarsomeres combined. Metatibia (Fig. 23C ) with 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 slightly oblique; few isolated patches of scale-like setae inserted posterior to last dorso-lateral comb. Metatibia with two spurs, outer spur shorter than inner one (Fig. 24F ). Metatarsomeres (Fig. 23C ) I-IV with row of spiniform setae consisting ventrally of 12 to 17 short, strong setae, formula: 17/14/12/15; metatarsomere I with two black and short lateral combs of scale-like setae and three isolated patches of black setae; metatarsomere II with one short lateral comb of scale-like setae and one black isolated seta, metatarsomeres III - IV without combs; length ratio of metatarsal segments 2.2-1.2-1-1. Pygidium long and straight, 2.4 × as long as hypopygium. Metanepisternum long and narrow, lower corner of posterior edge rounded, anterior edge 3 × as long as posterior edge, ventral edge 7.5 × as long as posterior edge (Fig. 24G ). Metakatepisternum restricted to ventral part of thorax, fused with median portion of posterior edge of metaventrite (Fig. 24G ). Pretarsal claws long and straight, with 2 indistinct teeth on ventral edge. Tip of pygidium with ring of short black scale-like setae. Lengths in mm: pronotal disc = 0.46, elytra = 1.29, mesotibia = 0.46, metatarsomere I = 0.38, pygidium = 0.73, body without head = ca. 2.

Figures

Figure 23. A-C. Holotype of † Baltistena nigrispinata Batelka, Troeger & Bock, sp. nov. (Mordellidae) preserved in piece PMJ Pa 5870. A. Habitus; B. Left antenna; C. Right metathoracic leg. Abbreviations: an 3 - an 11 = antennomeres 3 - 11, ta 1 - 4 = tarsomeres 1 - 4.

Figure 24. A-F. 3 D reconstruction of the holotype of † Baltistena nigrispinata Batelka, Troeger & Bock, sp. nov. (Mordellidae). A. Habitus in lateral view; B. Antennomeres I-VI; C. Maxillary palpomeres; D. Habitus dorsally (scutellar shield pointed by arrow); E. Pronotal disc; F. Metatibial spurs; G. Thorax laterally. Abbreviations: an 3 - an 6 = antennomeres 3 - 6, mtbs = metatibial spurs, mtcx = metacoxa, mtfe = metafemur, mte = metanepisternum, mtep = metepimeron, mttr = metatrochanter, mtke = metakatepisternum, mtve = metaventrite, mxp 2 - 4 = maxillary palpomeres 2 - 4, ped = pedicel, prn = pronotum, sca = scape, ta 1 - 4 = tarsomeres 1 - 4.

Figure A 6. Model 6 of the holotype of † Baltistena nigrispinata Batelka, Troeger & Bock, sp. nov. (Mordellidae) preserved in piece PMJ Pa 5870. An interactive cybertype is available in the HTML version of this article online and on Sketchfab: URL: https: // sketchfab. com / 3 d-models / baltistena-nigrispinata- 0 b 8819500 b 854 c 42 b 782 b 42 b 79 c 781 c 4.