The first described fossil species of Litargus Erichson (Coleoptera: Mycetophagidae) from Eocene Baltic amber examined with X-ray microtomography, and new records of Crowsonium succinium Abdullah, 1964

Abstract

A new species of Mycetophagidae belonging to the genus Litargus, namely L. (Litargosomus) dantiscensis Alekseev, Kupryjanowicz et Bukejs sp. nov., is described and figured from Eocene Baltic amber using X-ray micro-computed tomography (μCT). Three additional specimens of a mycetophagid beetle that is rather common in Baltic amber, Crowsonium succinium Abdullah, are also reported. Prototoma striata Heer, which was originally placed in Mycetophagidae, is discussed based on its original description and illustration: it is proposed that the position incertae sedis within Coleoptera be given to this Early Jurassic fossil. Consequently, the records of Mycetophagidae from Eocene European amber should be considered the earliest occurrence of the family known to date.

A new fossil species of Nausibius (Coleoptera: Silvanidae) in Rovno amber: a beetle from Eocene forests with congeners thriving in warehouses today

“…Such a high commonality at the family level (90%) between storage inhabitants found associated with products of plant and animal origin and coleopteran assemblages of Eocene ambers is hardly a mere coincidence. Among the beetle genera known from Eastern European Eocene ambers (Spahr, 1981;Alekseev, 2017;Alekseev et al, 2020;Háva & Zahradník, 2022), there are also numerous taxa that have living representatives among the coleopteran warehouse inhabitants, all with a cosmopolitan or very wide (due to human activity) distribution in the world. These include such genera as Anthrenus Geoffroy, 1762;Atomaria Stephens, 1829;Attagenus Latreille, 1802;Cartodere Thomson, 1859;Corticarina Reitter, 1881;Cryptophagus Herbst, 1863;Dienerella Reitter, 1911;Holoparamecus Curtis, 1833;Lasioderma Stephens, 1835;Latridius Herbst, 1793;Litargus Erichson, 1846;Micrambe Thomson, 1863;Nausibius Lentz, 1857;Ptinus Linnaeus, 1766;and Trogoderma Dejean, 1821.…”

Description of the male of fossil <i>Calomicrus eocenicus</i> Bukejs et Bezděk (Coleoptera: Chrysomelidae: Galerucinae) from Eocene Baltic amber using X-ray microtomography

“…Features such as wing development, antennal length ratios, the form and size of sense organs or mandibles, tarsal setation and dilatation, horns, teeth, and different structural modifications of the exoskeleton (like furrows, foveae, projections on pronotum and elytra etc. ), total body size, and colour variability are among the many well-known sexually dimorphic characters in Recent Coleoptera (Arrow, 1951;Crowson, 1981;Klausnitzer, 2002;Gullan and Cranston, 2014).…”

“…X-ray microtomography data obtained from lab-based machines or synchrotron beamlines have allowed sex determination in fossils without visibly exposed genitalia. The optically hidden, internal genitalia have been successfully studied in fossil species of Carabidae (Schmidt et al, 2016(Schmidt et al, , 2019Schmidt and Michalik, 2017), Latridiidae (Reike et al, 2017), Leiodidae (Perreau and Tafforeau, 2011;Perreau, 2012;Perreau and Perkovsky, 2014), Merophysiidae (Reike et al, 2020), Mycetophagidae (Alekseev et al, 2020b), Tenebrionidae (Nabozhenko et al, 2020), and other coleopteran families. To date, the sexual dimorphism that has been discovered in Eocene Baltic amber beetles can be characterized as "evolutionarily stable" and limited to characters known in present-day relatives: no new sexually dimorphic characters have been discovered in Eocene fossils.…”

“…Following classical views (e.g. Andrée, 1951;Poinar, 1992;Turkin, 1997), Baltic amber is thought to have been produced by Pinus succinifera (Göppert) Conwentz. Pinaceae along with different coniferous (Sadowski et al, 2017) and deciduous (primarily fagacean) trees, dominated the mixed forest cover of northern and central Europe in the warm-temperate, humid conditions of the Eocene.…”