A second fossil species of the enigmatic rove beetle genus Charhyphus in Eocene Baltic amber, with implications on the morphology of the female genitalia (Coleoptera: Staphylinidae: Phloeocharinae)

ABSTRACT Phloeocharinae is a small and likely non-monophyletic subfamily of rove beetles. The enigmatic genus Charhyphus Sharp, 1887 has long been placed in Phloeocharinae, whereas recent studies have found it to be phylogenetically very distant from the core members of this subfamily, suggesting the possibility that it actually deserves its own separate subfamily status. So far, the sole definitive fossil record for Charhyphus is known based on a single male from Eocene Baltic amber as represented by †Charhyphus balticus Shavrin, 2020. Here, we describe and illustrate another new Charhyphus species, †Charhyphus serratus sp. nov. Yamamoto & Shavrin, from Baltic amber based on a well-preserved female fossil. Considering the general proportions of the body and the head, this new species is most similar to †C. balticus. The new species differs from all known species by the development of strong serration of the lateral edges of the pronotum and features of the shape of the apical margin of the mesoventrite. By using X-ray micro-computed tomography, we succeeded in visualising not only the general habitus but also each individual body part, recovering a previously undocumented sclerite on the female internal genital segments in the genus. Morphological features of extinct and extant species of Charhyphus are briefly discussed. Figures of all extant Charhyphus species and a key for the genus are also provided. Our study is important for considering possible higher palaeodiversity, more common occurrence, and palaeobiogeography of Charhyphus.