Fossil Cymbiodyta from Baltic amber confirms Euro-American ancient distribution of the genus (Coleoptera: Hydrophilidae)

Abstract

We describe the first definite fossil of the water scavenger beetle subfamily Enochrinae (Coleoptera: Hydrophilidae): Cymbiodyta samueli sp. n. from the Eocene Baltic amber from the Lithuanian coast. The new species is extremely similar and likely closely related to the only European species, C. marginella and confirms the European occurrence of the genus since the Eocene. A reanalysis of the historical biogeography of the genus, including the fossil taxon, revealed a wide Euro-American distribution of the ancestor of all modern species of the genus, corresponding to the position of landmasses and existing land connections between North America and Europe in the Late Cretaceous. The biogeographic reconstructions and the fossil both suggest that European Cymbiodyta is an ancient relict lineage which used to be more diverse in the past but survived until today in a single species C. marginella .