Baltodascillus serraticornis, Kundrata & Gimmel & Packova & Bukejs & Blank, 2021

Kundrata, Robin, Gimmel, Matthew L., Packova, Gabriela, Bukejs, Andris & Blank, Stephan M., 2021, A new enigmatic lineage of Dascillidae (Coleoptera: Elateriformia) from Eocene Baltic amber described using X-ray microtomography, with notes on Karumiinae morphology and classification, Fossil Record 24 (1), pp. 141-149 : 143-145

Baltodascillus serraticornis sp. nov.

urn:lsid:zoobank.org:act:1839A0BD-37DB-4F9A-ABB9-12C8300682E1 ; Figs. 1–4 , Video supplements 1–4.

Type material

Holotype, adult male, NM-T 3470 ( NMPC, ex coll. R. Kundrata, Olomouc, No. BAL0012, ex coll. J. Damzen, Lithuania, No. 8751). A complete beetle is included in an elongate, transparent, yellow amber piece with dimensions of 32 × 15 × 4 mm, weighing approximately 1.7 g, without any syninclusions.

Type stratum and age

Mid-late Eocene, 48–34 Ma ( Seyfullah et al., 2018; Bukejs et al., 2019; Kasiński et al., 2020; Sadowski et al., 2017, 2020).

Type locality

Baltic Sea coast, Yantarny mine, Sambian (Samland) Peninsula, Kaliningrad Oblast, Russia.

Etymology

The specific epithet “ serraticornis ” is a Latin adjective referring to the shape of the antennae.

Diagnosis

As for the genus (vide supra).

Description

Adult male. Body ( Fig. 1 ) about 7.5 mm long and 2.5 mm wide, narrowly elongate, about 3 times as long as wide, weakly convex; dorsally moderately densely setose.

Head ( Figs. 2a, c, d ; 3 ; 4a, b ) 1.5 mm wide, subquadrate, 0.8 times as wide as pronotum width. Eyes large, strongly protuberant. Frontoclypeal suture distinctly impressed, more or less straight; clypeus short and strongly transverse. Labrum wider than long, distinctly sclerotized, anteriorly slightly concave, with discal setae longer than length of exposed portion of labrum. Antenna ( Figs. 1–3 ) serrate, almost reaching middle of elytra; scape slightly longer than pedicel; pedicel slightly longer than wide; antennomeres 3–10 elongate, with prominent, acute serrations; terminal antennomere simple, slightly curved, elongate, about 1.4 times as long as antennomere X, apically rounded. Mandible ( Figs. 2a , 3d ) considerably reduced, very short, subtriangular, without teeth, apically narrowly rounded. Maxillary palpus ( Figs. 2c, d ; 3 ; 4a, b ) moderately long; penultimate palpomere elongate, shorter than preceding one, about twice as long as wide; terminal palpomere fusiform, slightly longer than penultimate palpomere, about 2.5 times as long as wide, apically flattened and narrowly rounded. Labial palpus distinctly shorter than maxillary palpus, with terminal palpomere fusiform.

Pronotum ( Figs. 2b, c ; 3a, d ) transverse, about 1.7 times wider than long (1.9 mm wide, 1.1 mm long), widest just anterior to posterior angles; sides weakly arcuate; lateral carinae distinct, complete, slightly explanate; anterior angles obtuse, not projecting, posterior angles weakly acute; posterior edge tri-emarginate and weakly crenulate along entire length; disk slightly convex, with rather smooth surface. Hypomeron with postcoxal process obtuse. Prosternum ( Figs. 3b ; 4b, c ) in front of coxa about as long as procoxal diameter; prosternal process not developed, forming short right-angled denticle. Pronotosternal suture complete. Scutellar shield ( Figs. 1a ; 2b ; 3a ) slightly longer than wide, weakly rounded anteriorly, narrowly rounded posteriorly. Elytra ( Figs. 1a ; 2a, b ) together about 2.4 times as long as wide (5.9 mm long, 2.5 mm wide) and 5.0 times as long as pronotum; weakly convex, more or less straight, widest at apical third, then gradually narrowed basal half. Tergite X triangular, apically narrowly rounded. Aedeagus with only parameres visible but not median lobes.

Remark

We conclude that the examined specimen is a male based on the shape of the body, serrate antennae, a long, narrowly rounded abdominal ventrite 5, and aedeagal structure (parameres) detected in X-ray micro-CT imaging.

towards apex; elytral surface without costae or striae; elytral punctures irregular, only partially in weakly defined rows; elytral intervals flat; elytral epipleuron narrow and oblique behind humeral area. Mesoventrite ( Figs. 3b ; 4b, c ) with anterior edge medially on the same plane as metaventrite, forming short triangular projection laterally bordered by procoxal rests. Mesocoxal cavities separated by narrow mesoventral process. Metaventrite wider than long, moderately convex. Metacoxae contiguous, extending laterally to level of elytral epipleuron; metacoxal plate well developed mesally. Hind wing fully developed. Leg ( Figs. 1b ; 2d ; 4a, b ) slender, femur robust, elongate; tibia about as long as femur in fore- and midlegs, and slightly longer than femur in hind legs; each tibia with pair of distinctly serrate spurs approximately equal in length. Tarsomere 1 distinctly longer than tarsomere 2, tarsomeres 2–4 gradually shorter towards apex, each of tarsomeres 1–4 with membranous ventral lobe; lobes gradually larger from tarsomere 1 to tarsomere 4, those on tarsomeres 2–4 strongly bilobed ( Figs. 2e, f ; 4f, g ); claws simple, moderately curved; empodium absent.

Abdomen ( Figs. 1b ; 4d, e ) with five ventrites, with surface moderately densely covered by fine punctures; ventrites 1–4 gradually shorter towards apex; ventrite 1 without delimited hind coxal cavities, and with intercoxal process indistinct; ventrite 5 slightly longer than 4, triangular, narrowly rounded apically, apical half of ventrite in slightly different plane from

Figures

Figure 1. Baltodascillus serraticornis gen. et sp. nov., holotype: (a) habitus, dorso-frontal view; (b) habitus, ventro-lateral view. Scale bar = 2.0 mm.

Figure 2. Baltodascillus serraticornis gen. et sp. nov., holotype: (a) habitus, lateral view; (b) pronotum and scutellar shield, dorsal view; (c) head and pronotum, dorsal view; (d) head and thorax, ventral view; (e) tarsus, ventro-lateral view; (f) tarsus, ventral view. Scale bars = 1.0 mm (a–d), 0.3 mm (e, f).

Figure 3. Baltodascillus serraticornis gen. et sp. nov., holotype, Xray micro-CT renderings:(a) head and thorax, dorsal view; (b) head and thorax, ventral view; (c) head and thorax, right lateral view; (d) head and thorax, left lateral view. Scale bars = 1.0 mm.

Figure 4. Baltodascillus serraticornis gen. et sp. nov., holotype, X-ray micro-CT renderings: (a) head, frontal view; (b) head and thorax, fronto-ventral view; (c) pro- and mesothorax, ventral view; (d) abdomen (ventrites 2–5), lateral view; (e) abdomen (ventrites 2–5), ventral view; (f) tarsus, ventral view; (g) tarsus, dorsal view. Scale bars = 1.0 mm.