The extant liverwort Gackstroemia (Lepidolaenaceae, Porellales) in Cretaceous amber from Myanmar

• We report a fossil of a leafy liverwort from the Cretaceous of Myanmar.
• The fossil is assigned to the extant genus Gackstroemia.
• It represents the second extant genus of leafy liverworts from the Cretaceous.

We describe a sterile gametophyte fragment of a leafy liverwort preserved in Cretaceous amber from Myanmar, and place it in the extant genus Gackstroemia, as G. cretacea sp. nov., representing the second extant genus of leafy liverworts reported from the Mesozoic. The complicate bilobed leaves of the fossil have a ventral lobule forming a ciliately toothed, Frullania-type water sac, and a dorsal lobe carrying a single apical cilium, as well as bifurcate underleaves being either flat or developed as a pair of ciliately toothed water sacs. Gackstroemia cretacea is the first fossil record of Lepidolaenaceae, a family being at the present time confined to the southern temperate zone. The new fossil adds to growing evidence that southern disjunctions cannot exclusively be explained by Gondwanan vicariance and that the range of Lepidolaenaceae once included parts of Laurasia.