Kaolakia borealis nov. gen. et sp. (Porellales, Jungermanniopsida): A leafy liverwort from the Cretaceous of Alaska

Mesozoic bryophyte fossils are rare and often assigned to form genera only. Here, we describe a fragment of a leafy liverwort preserved in Cenomanian amber from northern Alaska, and place it in a new genus, Kaolakia. The extinct species Kaolakia borealis resembles the extant Frullaniaceae in having perianths with a beak, as well as complicate-bilobed incubous leaves with a Frullania-type water sac; however, two water sacs are consistently present on each side of the stem. This character resembles Lepidolaenaceae and Goebeliellaceae, although the extant members of these families have coelocaules or truncate perianths. Thus our fossil likely represents an extinct lineage with affinities to Porellales, the primarily epiphytic clade of the leafy liverworts, and is possibly closely related to Frullaniaceae.

► We report the first leafy liverwort from the mid Cretaceous of Alaska.
► The fossil stands out by incubous foliation, beaked perianths, and four watersacs per leaf pair.
► This morphology resembles extant Porellales.
► The combination of character states does not fit any extant genus.
► Hence, Kaolakia borealis n. gen. et sp. is described, with relationships to extant Frullaniaceae.