Abstract
Beetle fossils are a rich source of information about the palaeodiversity and evolutionary history of the order Coleoptera. Despite the increasing rate of fossil research on click-beetles (Coleoptera: Elateridae), the most diverse group in the superfamily Elateroidea, their fossil record has remained largely unstudied. This may be caused by the combination of their rather uniform external morphology and the suboptimal state of preservation and visibility in most fossil specimens. Here, we used X-ray micro-computed tomography to reconstruct the morphology of an interesting click-beetle from Eocene Baltic amber, which had some principal diagnostic characters obscured by opaque bubbles and body position. Our results suggest that the newly described Baltelater bipectinatus gen. et sp. nov. belongs to tribe Protelaterini within subfamily Lissominae. Since Protelaterini have a predominantly Gondwanan distribution, our discovery is of a great importance for the historical biogeography of the group. Very distinctive are the bipectinate antennae with 11 antennomeres and with rami beginning on antennomere IV, which are not found in any recent Elateridae. The discovery of a new click-beetle lineage from European Eocene amber sheds further light on the palaeodiversity and historical diversification of the family as well as on the composition of the extinct amber forest ecosystem.
Highlights
Over recent decades, there has been an increasing amount of research attention directed towards insect fossils
Based on its divergent morphology (Figs. 1–5, Supplementary Videos 1–3), we describe here Baltelater bipectinatus gen. et sp. nov., which we classify in the tribe Protelaterini within the click-beetle subfamily Lissominae
The fossils entombed in the relatively young Eocene European ambers are almost always classified within present-day suprageneric taxa, and approximately half of them in extant g enera[28]
Summary
There has been an increasing amount of research attention directed towards insect fossils. Micro-CT data were used in palaeontological studies focused on the morphology of various fossil animal taxa, including, for example, arachnids17,18, myriapods19, crustaceans20, insects[3,21], and v ertebrates[22,23] This method is used for habitus observation but often for reconstruction of internal organs including genitalia, as documented by a number of recent papers dealing especially with Baltic amber Coleoptera[24,25,26,27]. Elateridae comprise more than 10,000 extant species worldwide[42], and the fossil record includes approximately 300 species, the placement of many of them needs thorough investigation[48,49] They originated and greatly diversified during the M esozoic[2,50,51], and are among the most common beetle families recorded in Baltic a mber[28,52]. The discovery of the first lissomine click-beetle from European Eocene amber sheds further light on the palaeodiversity and historical diversification of the family as well as on the composition of the extinct amber forest ecosystem
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