Omineus febribilis Alekseev, Pollock & Bukejs, 2019

Alekseev, Vitalii Igorevich, Bukejs, Andris & Pollock, Darren Andrew, 2020, A new fossil Eurypinae genus and sexual dimorphism in the representatives of Omineus (Coleoptera: Mycteridae) from Tertiary amber of Europe, Zootaxa 4820 (3), pp. 551-562 : 556-558

Omineus febribilis Alekseev, Pollock & Bukejs, 2019

Material examined. One specimen with collection number 4438-27 [ KRAM]; Baltic amber, adult, female (ab-dominal ventrite 2 without sex patch), complete specimen. The beetle inclusion is preserved in a medium-sized polished piece of transparent amber with dimensions of 35×13× 9 mm without supplementary fixation. Syninclusions are represented by numerous fagacean stellate trichomes. Body length of the specimen is 3.5 mm (the holotype is 3.1 mm long), but other main characters of the specimen fully correspond to that of Omineus febribilis Alekseev, Pollock & Bukejs, 2019 and the specimen is attributed to this species .

One specimen with collection number AWI-059 [ CVIA] ( Figs. 6–8 ); Baltic amber, adult, male (abdominal ven-trite 2 with sex patch), complete specimen. The beetle inclusion is preserved in an elongate-oval, polished piece of transparent amber with dimensions of 25×13× 6 mm without supplementary fixation. Syninclusions are represented by a few stellate trichomes of plant origin, minute gas vesicles, and one Acari specimen. Body length of the specimen is 2.8 mm.

One specimen with collection number JD 8369 [ JDC] ( Figs. 9–14 ); Baltic amber, adult, male (abdominal ven-trite 2 with sex patch), complete specimen. The beetle inclusion is preserved in an elongate, polished piece of transparent amber with dimensions of 15×9× 8 mm without supplementary fixation. Syninclusions include a few stellate trichomes of plant origin. Body length of the specimen is 2.9 mm.

Note. Specimen No. AWI-059 [ CVIA] was reported in Alekseev et al. (2019) and identified as belonging to Eurypinae without further generic attribution. The X-ray micro-CT scans provide sufficient data, which led us to consider the specimen to be a male of Omineus . The absence of clear differences in external morphology between this male specimen and the holotype (female), as well as the similarities in structural detail to specimen JD 8369, also identified as a male of the Omineus , led us to conclude that all specimens represent a single fossil species from Baltic amber, Omineus febribilis . The availability of two additional males and one female allow us to provide the sexually dimorphic characters for diagnosis of the fossil O. febribilis , originally described on the basis of the female specimen only.

The size variability of the extinct species (2.8–3.5) is established based on the presented material: apparently, the males are shorter (2.8–2.9 mm), the females are longer (3.1–3.5 mm). The eyes of the male are slightly larger and more protruding, and the frons is narrower in the male, compared to the female. Abdominal ventrite 2 of the male has a prominent sex patch, mesally gibbose but not clearly delimited, without especially dense setae, almost as long as the mesal length of ventrite 2. The apical margin of the male pygidium is weakly and widely emarginate medially.

Figures

FIGURES 6–8. Omineus febribilis, AWI-059 [CVIA], male, habitus, X-ray micro-CT rendering: 6—dorsal view; 7—ventral view; 8—lateral view. Scale bars represent 1.0 mm.

FIGURES 9–10. Omineus febribilis, 8369 [JDC], male, habitus, photomicrograph: 9—dorsal view; 10—left lateral view. Scale bars represent 1.0 mm.

FIGURES 11–14. Omineus febribilis, 8369 [JDC], male, habitus, X-ray micro-CT rendering: 11—dorsal view; 12—left lateral view; 13—ventral view; 14—frontal view. Scale bars represent 1.0 mm.