Pallaviciniites oishii(comb. nov.), a thalloid liverwort from the Late Triassic of Japan

Abstract

Abstract The fossil liverwort Hepaticites oishii from the Momonoki Formation in Western Honshu, Japan is critically reviewed. The type material exhibits the following characteristics: (1) small thalloid plants with well-defined midrib and lamina; (2) regularly dichotomously branching habit; (3) attenuate apical part of thallus with unnotched apex; (4) lack of ventral scales; (5) undulate lamina and margin of thallus without marginal teeth or hair; and (6) presence of rhizoids on midrib. These characters suggest an affinity of H. oishii to members of simple thalloid liverworts, particularly Pallaviciniales (Jungermanniopsida, Marchantiophyta). The species is therefore assigned to the fossil genus Pallaviciniites with a new combination: Pallaviciniites oishii (Huzioka & Takahasi) T. Katag. This liverwort fossil is significant because it constitutes the first fossil record of the order Pallaviciniales from the Late Triassic of Eurasia and is the second-oldest fossil liverwort in East Asia after Riccardiothal...