The leafy liverwort Frullania (Jungermanniopsida) in the Cretaceous amber forest of Myanmar

Examination of two pieces of amber from the mid-Cretaceous of Myanmar revealed seven inclusions of leafy liverworts that we assign to the extinct Frullania cretacea Hentschel et al. 2009. These inclusions show a suite of characters that were not visible in the type specimen of F. cretacea. The new gametophytes consistently display rectangular to ovate underleaves that have two long-ciliate apical teeth in addition to 0–2 blunt lateral teeth. A narrow stylus is present on at least some leaves. The lobules usually form water sacs that are 1.2–2.3 times longer than wide, and are arranged at some distance from the stem. The observed combination of character states is not present in extant crown group lineages of Frullania. A syninclusion in one of the amber pieces is interpreted as a detached gynoecium of a second Cretaceous Frullania species and is described as F. baerlocheri, sp. nov. The subgynoecial underleaves of the syninclusion are suborbicular in shape, and allow for a separation of this species from F. cretacea. The described amber inclusions are the oldest representatives of an extant genus of leafy liverworts known so far.

► We report amber inclusions of liverworts from the mid Cretaceous of Myanmar.
► The fossils are assigned to the extant genus Frullania.
► Underleaves, styli and fertile structures of Frullania cretacea are described for the first time.
► One inclusion is interpreted as a detached gynoecium and described as Frullania baerlocheri sp. nov.