The oldest case of paedomorphosis in rove beetles and description of a new genus of Paederinae from Cretaceous amber (Coleoptera: Staphylinidae).

The ecology of extinct species from the Cretaceous is largely unknown. Morphological features of specimens preserved in amber can help to reveal habitats and evolutionary strategies that occurred in fossil lineages. An unusually small rove beetle (Staphylinidae) from the subfamily Paederinae with a Y-shaped suture on the head and modified tarsi and antennae is newly described here as Midinudon juvenis Tokareva & Żyła gen. et sp. nov. We hypothesise that such a combination of characters represents the earliest example of paedomorphosis in Staphylinidae and discuss other possible reasons that could explain the small size and morphological modifications of the new species. We provide the results of total-evidence phylogenetic analysis and discuss the relationships of Midinudon juvenis Tokareva & Żyła gen. et sp. nov. within Paederinae.