The leafy liverwort Notoscyphus balticus sp. nov. (Jungermanniales) in Eocene Baltic amber

• A sterile leafy liverwort in a piece of Eocene Baltic amber is described.
• The fossil is assigned to the extant genus Notoscyphus.
• Notoscyphus balticus sp. nov. represents the oldest known Geocalycaceae fossil.

We describe a sterile gametophyte fragment of a leafy liverwort in a piece of Eocene Baltic amber possessing clustered rhizoids, succubously inserted, alternating, entire leaves, papillose stem and lamina cells, and bifid underleaves not coadunate to the leaves. The fossil is assigned to the extant genus Notoscyphus and treated as Notoscyphus balticus sp. nov. It differs from extant representatives of Notoscyphus by its uniformly brown colour, rhizoids with a diameter of 15–23 μm and small leaf cells (ca. 17–25 μm × 17–30 μm at midpoint). Putative septate rhizoids of the fossil are more likely unicellular rhizoids covered with thin fungal hyphae that can easily be confused with septa.