A new genus of filicalean fern from the Lower Permian of China

Abstract

Recent investigation on the Cathaysian flora of the Lower Permian Taiyuan Formation in Hebei Province, North China has led to the discovery of a new type of fern, Rastropteris pingquanensis gen. et sp. nov. Preserved as a permineralization, the stem, with a mantle of petiole bases and roots, shows a unique combination of anatomical characters. The vascular strand consists of a solid protostele with uniformly elongated tracheids and mesarch maturation of the xylem. In transverse section, the configuration of leaf trace xylem changes from reniform endarch to a tangentially elongated strand adaxially recurved at each end with several adaxial ridges. Stem and petiole cortex contains abundant sclerotic tissue with an interstitial tissue developed within the mantle of petiole bases and roots. A reinvestigation of Grammatopteris rigollotii, from the Permian of France, the type species of the genus allows interpretation of the latter as closer toRastropteris than any other fern. Both taxa are provisionally reported to an incertae sedis group of filicalean ferns possibly involved in the origin of Osmundaceae.