Europs carsteni, Alekseev & Bukejs, 2025

Alekseev, Vitalii & Bukejs, Andris, 2025, The third extinct representative of the genus Europs Wollaston, 1854 (Coleoptera: Nitiduloidea: Monotomidae) in Baltic amber, Zootaxa 5620 (4), pp. 575-581 : 576-580

Europs carsteni sp. nov.

( Figs 1–5 )

Type material. Holotype: No. GPIH no. 5219 , CCGG no. 8708 (ex coll. Jonas Damzen JDC-13132); “Holotype / Europs carsteni sp. nov. / Alekseev V. et Bukejs A. des. 2025” [red printed label]; adult, female (abdomen with 5 ventrites only, without narrow genital capsule segment). A complete beetle with partially exposed metathoracic wings is included in a transparent, yellow amber piece with dimensions of 25× 4 mm and a maximum thickness of 3 mm; preserved without supplementary fixation. Syninclusions: a few stellate Fagaceae trichomes.

Type stratum. Baltic amber from Eocene amber-bearing Blaue Erde deposits; estimated age: Middle–Late Eocene ( Standke 1998; Sadowski et al. 2017, 2020; Seyfullah et al. 2018; Bukejs et al. 2019; Kasiński et al. 2020).

Type locality. Yantarny village (formerly Palmnicken ), the Sambian ( Samland ) peninsula, the Kaliningrad Region, western Russia.

Description. Measurements: total body length (including head and visible part of pygidium) 1.8 mm, maximum body width (across elytra) 0.5 mm; head length 0.3 mm, head width (across eyes) 0.4 mm; pronotal length 0.5 mm, maximum pronotal width 0.5 mm; elytral length (along elytral suture, including scutellum) 0.9 mm, elytra maximum width 0.5 mm. Body narrow-elongate, weakly convex; integument matte, unicolorous brown (as preserved); pubescence: elytra and pronotum with fine, semierect setae.

Head prognathous, transverse, 1.3× wider than long; with coarse and dense punctation, distance between punctures smaller than diameter of one puncture, some punctures contiguous, punctures distinctly smaller and sparser medially; interspaces microreticulated. Neck distinct. Temples short, with length of about 0.3× longitudinal diameter of eye, rounded. Compound eyes lateral, nearly hemispherical, rather large, moderately convex, with small facets. Frons flat. Frontoclypeal suture absent. Forehead with deep, semioval impression. Antennal insertions lateral, concealed dorsally by projections of frons. Antennae rather short, extending to anterior one-fourth of pronotum length; antennae appearing 10-segmented (because antennomeres 10 and 11 fused, with distinct suture between them) with 2-segmented club; antennomere 1 cylindrical, about 1.5× longer than wide; antennomere 2 cylindrical, slightly dilated apically, 1.4× longer than wide, wider and longer than antennomere 3; antennomere 3–6 subtrapezoidal, slightly dilated apically, as long as wide; antennomeres 7–8 subtrapezoidal, dilated apically, slightly transverse, 1.1–1.2× wider than long; antennomere 9 trapezoidal, dilated apically, transverse, about 1.5× wider than long, distinctly wider than antennomere 8, nearly as wide as antennomere 10; antennomere 10 (composed of fused antennomeres 10 and 11) subovoid with narrowly rounded apex, elongate, 1.2× longer than wide; relative length ratios of antennomeres 1–10 equal to 15:13:6:6:6:6:7:7:10:21. Antennal grooves absent. Maxillary palpi with terminal palpomere fusiform; palpomere 2 not enlarged.

Pronotum subquadrate, as long as wide, subparallel-sided, maximum width in middle of pronotum length, slightly narrowed anteriad and posteriad. Pronotal disc flat; without grooves; with wide, longitudinal, impunctate area medially, about 3.7–4.2× as wide as diameter of one pronotal puncture. Anterior margin straight, narrowly bordered; posterior margin weakly emarginated medially, widely bordered; lateral margins weakly rounded, finely crenulate. Anterior angles obtuse, rounded, not protruding; posterior angles rounded. Pronotal punctuation round, coarse (as large as head punctation) and dense, distance between punctures equal to about 0.1–0.5× diameter of one puncture; interspaces densely microreticulated. Prothorax convex, covered with small, sparse punctures and microreticulation. Protrochantins concealed. Procoxal cavities widely closed externally. Prosternal process large, elongate, extending beyond procoxae, convex, with sharp sulcus at lateral sides, strongly dilated posteriorly, sinuate laterally; posterior margin truncate, length about 1.3× transverse diameter of procoxa; apparently impunctate.

Scutellar shield subpentagonal with apex rounded, elongate, apparently without setigerous punctures.

Elytra rather short, 1.8× as long as pronotum length, elongate, 1.8× longer than wide, subparallel-sided, widest at middle; truncate apically, completely exposing last abdominal tergite; elytral base emarginated, distinctly wider than pronotal base. Elytral punctation elongate, fine (punctures in basal one-third distinctly larger than punctures at apex), dense, arranged in regular striae (each elytron apparently with nine striae); inflexed part of elytron apparently with three striae; interstriae flat, wide, densely microreticulate; elytral intervals 3 and 5, as well other intervals without additional setigerous punctures in anterior half. Epipleura widest at humeri and gradually narrowed posteriorly, with fine and sparse punctation, not reaching to elytral epex. Mesocoxal cavities open. Metepisternum elongate subtriangular, widest anteriorly, 7.5× longer than wide, with large and dense punctures. Metaventrite with disc convex, sparsely covered with small punctation and microreticulation; discrimen fine, distinct in posterior three-fourth. Metathoracic wings present.

Legs moderately long, covered with fine punctation. Procoxae nearly round, narrowly separated by about 0.6× longitudinal diameter of procoxa; mesocoxae widely oval, slightly transverse, separated by about 1.3× longitudinal diameter of metacoxa; metacoxae oval, transverse, widely separated by 1.4× longitudinal diameter of metacoxa. Femora nearly spindle-shaped, swollen medially. Tibiae slightly curved, gradually widened apically, with two short apical spurs. Tarsi slender, tarsal formula apparently 5-5-5; penultimate tarsomere not bilobed, very small; ultimate tarsomere subcylindrical, slightly curved, longer than all previous tarsomeres combined. Pretarsal claws simple, thin.

Abdomen elongate, with five visible ventrites, covered with small (nearly as large as punctures of metaventrire) and sparse punctuation (ventrite 5 with distinctly denser punctation), interspaces with microreticulation. Ventrite 1 longest, distinctly longer than ventrites 2–4 combined; without median setigerous plaque; intercoxal process subtrapezoidal, wide, about 1.4× longitudinal diameter of metacoxa, with rounded apex; femoral lines triangularly produced, with longitudinal extension, produced beyond the middle of abdominal ventrite 1. Ventrites 2–4 short, subequal in length. Ventrite 5 simple, without median depression, with widely rounded posterior margin. Relative length ratios of abdominal ventrites 1–5 equal to 29:6:5:5:15 (measured medially). Last visible tergite densely covered with small punctation; with widely rounded apex.

Differential diagnosis. Europs carsteni sp. nov. differs from extant species of the genus based on the following combination of characters: relatively small body size (1.8 mm); triangular femoral lines with long longitudinal linear extension produced beyond the middle of abdominal ventrite 1; pronotal disc without grooves and with wide, longitudinal, impunctate area medially (in contrast to E. ferrugineus Reitter from Japan, sometimes placed in separate subgenus or even genus Monotopion Reitter, 1884 ); elytra and pronotum with fine, semierect setae; temples short (character used in delimination of the species, however the length and shape of temples gradually can vary within several extant species of the genus and is also a secondary sex characteristic); and subquadrate pronotum.

The new fossil species can be readily distinguished from described extinct representatives of genera Aneurops (one species in Baltic amber) and Europs (three species in Baltic and Mexican ambers) in the finely setose dorsum and triangularly produced femoral lines with longitudinal extension. Europs carsteni sp. nov. differs from Rovnoeurops mckellari Alekseev et Bukejs, 2022 (Rovno amber) in medially non-impressed pronotum, and antennomeres 5–8 not strongly transverse.

Derivatio nominis. The specific epithet is a patronym; the new species is named in honor of Mr. Carsten Gröhn (Glinde, Germany), an enthusiast and specialist in Baltic amber.

Figures

FIGURES 1–3. Europs carsteni sp. nov., holotype, No. 5219 [GPIH]: 1—habitus, dorso-lateral view; 2—habitus, ventro-lateral view; 3—habitus, left lateral view. Scale bars = 0.5 mm.

FIGURES 4–5. Europs carsteni sp. nov., holotype, No. 5219 [GPIH]: 4—head, dorsal view; 5—details of abdomen. Abbreviations: a1–a11—antennomeres 1–11, respectively; ey—compound eye; fl—femoral line; mc—metacoxa; te—temple; v1—abdominal ventrite 1 without median setigerous plaque. Scale bars = 0.1 mm.