Eoractocetus storozhenkoi, Kirejtshuk, 2025

Eoractocetus storozhenkoi gen. et sp. nov.

( Figs 1–12 View FIGURES 1–2 View FIGURES 3–4 View FIGURES 5–6 View FIGURE 7 View FIGURES 8–9 View FIGURE 10 View FIGURES 11–12 )

Type material. Holotype “8761” (KAM); adult, female.A rather complete beetle with completely exposed ovipositor included in a transparent, yellow amber flat piece with black number “8761”, which has a subtrapezoid shape with somewhat arcuate greatest side ( 15 mm) becoming thinner, while other sides (6.8 x 7.7 x 7.7 mm) are straight nearly vertically cut. Along the beetle body plan some flat cracks mixed with traces of resin layers, having whitish color and opaque and making examination of the beetle difficult and some details almost impossible. Besides, there are many brownish to yellowish small pieces of organic matter with different shape and size, and also with very small gas bubbles disorderly spread in amber.

Type locality. Yantarny settlement (formerly Palmnicken), Sambian (Samland) Peninsula, Kaliningrad Region, Russia .

Type stratum. Late Eocene, Priabonian (probably 36.8–36.4 Ma).

Description. Body length with head somewhat declined down 7.6 mm, width 1.5 mm, height 1.2 mm. Body elongate and narrow, rather convex as dorsally as ventrally. Integument rather dark, nearly blackish, dorsal surface densely and shortly pubescent with fine subrecumbent hairs about as long as or somewhat longer than distance between their insertions, punctures about as coarse as third to fifth of eye facets and interspaces between them extremely finely microreticulated; metaventrite, metacoxae and first abdominal ventrites with almost inconspicuous hairs, more finely and sparsely punctured than dorsal ones, interspaces between punctures alutaceous; other parts of underside integument and femora with pubescence similar to that on dorsal sclerites, other sclerites of legs more densely pubescent with longer hairs and antennomeres particularly densely pubescent with rather long hairs.

Head declined and visible mostly from below, rather large with very large eyes of coarse facets, narrowly separated dorsally, their rather deeply incised around antennal insertions and postocular portion of epicranium rather reduced and partly covered with anterior part of pronotum. Labrum rather large, trapezoid and widening anteriorly. Maxillary palps with moderately raised elongate palpomere 4 and unclearly observable maxillary palporgan due to “milky” opaqueness. Antennae moniliform, consisting of antennomeres 2–10 thickening apically and with largest (thickest) antennomeres 3–6, antennomere 11 fusiform and markedly longer and narrower than each of antennomeres 2–10.

Pronotum elongate and gently convex along middle of anterior part, with one pair of shallow paramedian depressions at middle and with narrow depression along entire length, about 1.5 times as long as wide and subparallel-sided at base, anterior angles not expressed not at all, anterior edge strongly convex and gently rounded, posterior angles strongly projecting posteriorly (markedly surpassing level of convexity of posterior edge of pronotum). Scutellum transversely subtriangular to subpentangular and widely rounded at apex, with subcordiform median plate narrowed at base, slightly longer than wide and not reaching scutellar apex. Elytra about 2.5 times as long as pronotum, each elytron almost fifth as wide as long, without trace of venation. Exposed tergites somewhat longer than wide and laterosternites rather narrow. Pygidium slightly narrowing posteriorly, more than 1.5 times as long as wide, subpentagonal and subacute at apex.

Prosternum along middle about third as long as mesoventrite, with anterior sclerotized edge deeply excised and extermely short precoxal portion (something like that in Atractocerus ). Procoxae about twice as long as wide and with gently convex posterior edge. Mesocoxae very long, with subparallel anterior and posterior edges, three times as long as wide, their inner edges subparallel to each other (but not closely). Metaventrite more than 1.5 times as long as wide, with posterior edge strongly projecting posteriorly. Metacoxae rather “narrow” (distance between anterior and posterior edges), strongly obliquely declined to apices, their subcontiguous parts comprising third of entire metacoxal length, subtruncate at apex. Abdominal ventrite 1 between metacoxal apices and its posterior edge markedly shorter than each of other abdominal ventrites (2–5), ventrites 2–4 somewhat transverse. Hypopygidium (ventrite 5) less than 1.5 times as long as wide, widely rounded at posterior edge.

Legs with very long and thin femora, tibiae and tarsomeres.

Considerable part of hind wings visible, somewhat folded and spread along posterior edge, fused C-Sc-R vein rather stout, distal part of hind wind observable and showing two long anal veins reaching posterior edge, M and Cu distinctly separated, wedge-cell well raised and r-m crossvein very distinct, but radial cell not traced.

Ovipositor moderately sclerotized and with styli as long as width of ovipositor apex.

Etymology. The epithet of the new species is devoted to the seventieth birthday of Sergey Yu. Storozhenko (Vladivostok, Russia).

Notes. This species has apparently rather short postocular portion of epicranium which is covered with the anterior part of pronotum. The lymexylid head is moving thanks to a more or less considerable reduction of anterior sclerotized part of the prosternum, as a result, a large membranous window is formed, facilitating significant head mobility. Having looked through thousands of named and unnamed specimens in the Zoological Institute of RAS collection, the author did not find any specimen with the head retracted into the prothoracic segment, because the anterior pronotal edge is usually much narrower than the head. Another peculiarity of the examined specimen is some convexity of pronotum along the middle, while other examined lymexylid specimens are characterized by more or less straight pronotum in lateral view or even concave at anterior edge (probably for an additional fixation of the posterior part of epicranium). The next peculiar feature of this specimen is its posterior pronotal angles strongly projecting posteriorly, as is known in fossil Cretoquadratus and modern Hymaloxylon Kurosawa, 1985 , while other lymexylids have at most slightly projecting posterior angles or frequently obtuse to rounded ones.