Mosses from Rovno amber (Ukraine), 6. New genus of the family Pylaisiadelphaceae

Rovno and Baltic amber inclusions are known as a rich source of late Eocene mosses. Most of them are either referred to extant genera or placed in form-genera with names meaning similatity to an extant taxon. The present moss from Rovno amber is rather exceptional, having combination of features different from any extant mosses known for us. Therefore it is described as Rovnohypnum gen. nov., characterized by medium-sized plants, non-branched shoots that are attenuate to their tips, moderately loosely foliate, leaves spreading, ovate, acuminate, cordate at base, costa double, cells elongate, with one to three prominent papillae on dorsal surface, smooth or much weaker papillose on ventral side, proximal branch leaves subdivided into subfilamentose lobes. Putative brood filaments are noticed in many leaf axils. We compare this moss with the Pylaisiadelphaceae, where the brood filaments, pluripapillose cells, and filamentose or subfilamentose structures surround the branch primordia. However, these traits are characteristic for different genera of the family, thus we refer it in a new genus within the Pylaisiadelphaceae.