Eledonoprius incoronatus, 2020

Alekseev, Vitalii I., Bukejs, Andris & Sontag, Elżbieta, 2020, A new fossil species of Bolitophagini (Coleoptera: Tenebrionidae) from Baltic amber suggests the genus Eledonoprius Reitter is persistent in the Western Palaearctic since the Tertiary, Zootaxa 4750 (3), pp. 418-424 : 419-423

E. incoronatus Alekseev & Bukejs sp. nov.

( Figs. 1–6 )

Type material. Holotype: MAIG 6012 , adult, male, complete beetle inclusion with partially exposed male genitalia.

Type locality and horizon. Yantarny settlement (formerly Palmnicken), Sambian (Samland) peninsula, the Kaliningrad region, Russia. Baltic amber. Mid-Eocene (Bartonian) .

Description. Body oblong, subparallel-sided, moderately convex dorsally; uniformly black, coarsely punctate, bare. Total body length about 2.14 mm; maximum length of pronotum 0.5 mm; pronotal maximum width 1.1 mm; length of an elytron along suture 1.3 mm; width of elytra at humeri 1.1 mm.

Head transverse; frontoclypeus widely rounded and non-denticulate anteriorly, with two short straight sharp horns and inconspicuous sparse short setae; genae broader than eyes, non-denticulate; frons almost flat, with four distinct sharpened tubercles located in concave arcuate line between posterior margins of eyes; vertex slightly convex. Punctation of head dense and rounded. Compound eyes oval, with vertical diameter about 2× transverse diameter, very deeply emarginate by genae anteriorly (almost divided in two parts: dorsal and ventral); without interfacetal setae. Terminal maxillary palpomere cylindrical, about 4.0× as long as wide, longer than two previous palpomeres combined. Antennae 11-segmented, comparatively short; antennomeres 6–8 almost quadrate; antennomeres 9–10 transverse; antennomere 11 longest, oval, about 1.8× as long as antennomere 10, slightly shorter than antennomeres 9 and 10 combined.

Pronotum strongly transverse, about 2.2× as wide as long, with maximum width in posterior one-third, as wide as elytral base; pronotal disc moderately convex, with two shallow, indistinct oblique latero-basal impressions; lateral margins widely explanate, slightly rounded, with 5–6 sharp triangular denticles; posterior margin bisinuate; anterior margin deflexed, arcuate; anterior pronotal angles distinct, triangular, produced forwards; posterior angles distinct, almost orthogonal. Pronotal surface with rough, rounded, dense punctation, interspersed with sharp granules. Procoxae narrowly separated by prosternal process.

Elytra elongate, slightly widened postmedially; disc moderately convex; humeral angles well-developed, rounded. Each elytron with 9 deep striae; elytral punctation very shallow and discernible in basal one-quarter, obliterate apically. Interstriae convex, with distinct sharp granules in posterior one-third and obtuse granules on the disc. Humeral interval with sharp granules along the entire length. Scutellar shield as long as wide, rounded apically. Epipleura wide (epipleuron in basal part distinctly wider than metanepisternum), gradually narrowing posteriorly.

Legs slender. Femora and tibiae moderately flattened; tibia with one very short spine apically. Tarsal formula 5-5-4. All tarsomeres simple (non-lobed); tarsomere 1 longer than all previous tarsomeres combined; tarsal claws long, falcate, about 0.5× as long as last tarsomere.

Abdomen with five ventrites, coarsely and densely punctate, bare. Anterior process of ventrite 1 triangular. Distal parts of male genitalia visible.

Etymology. The epithet of this new species [Latin adjective “ incoronatus ” – uncrowned, deprived of the crown] refers to its non-denticulate frontoclypeus and genae.

Differential diagnosis. Eledonoprius incoronatus sp. nov. is placed in the genus Eledonoprius within the tribe Bolitophagini on the basis of the following morphological characters: small size (slightly larger than 2 mm); pronotal lateral sides widely explanate, denticulate and not-margined; anterior pronotal angles distinct but not strongly produced forwards; elytral intervals and pronotal surface with sharp granules; eyes distinctly and deeply emarginate by genae anteriorly; head with pair of short horns; epipleuron distinctly wider than metanepisternum.

The newly described fossil species clearly differs from the extant European Eledonoprius serrifrons (Reitter) and E. armatus (Panzer) in having the frontoclypeus and genae without denticulation (in contrast both extant species have distinct, well-developed denticulation on the head anteriorly); less numerous lateral denticles of pronotum; apical antennomere shorter than antennomeres 9 and 10 combined; and smaller body size.

Remarks. The new species superficially resembles (possibly, due to evolutionary parallelism and adaptation to similar ecological niche) the zopherid species Endophloeus gorskii Alekseev & Bukejs, 2016 from Baltic amber ( Alekseev & Bukejs 2016), but differs in is glabrous body (elytra with apparent scale-like setae in Endophloeus ), tarsal formula 5-5-4 (4-4- 4 in Endophloeus ), antennae without distinct club (in contrast to distinct 2-segmented club in Endophloeus ), and more transverse pronotum.

Figures

FIGURES 1–2. Eledonoprius incoronatus sp. nov., holotype: 1 – habitus, dorsal view; 2 – habitus, lateral view. Scale bars represent 0.5 mm.

FIGURES 3–4. Eledonoprius incoronatus sp. nov., holotype: 3 – habitus, ventral view; 4 – forebody, ventral view. Scale bars represent 0.5 mm (Fig. 3) and 0.2 mm (Fig.4).

FIGURES 5–6. Eledonoprius incoronatus sp. nov., holotype: 5 – genitalia, lateral view; 6 – forebody, lateral view. Scale bars represent 0.2 mm.