Diodonopteris, a new genus of the Paleozoic leptosporangiate fern family Botryopteridaceae, from the lower Permian of Shanxi Province, North China

• A new genus of Botryopteridaceae with two rachis protoxylem groups
• First account of botryopterid plant fossils with stems, petioles and rachides preserved from the Permian of China
• The new species probably has a semi-upright habit.

Anatomically preserved botryopterid specimens from Cisuralian (early Permian) aged coal balls in Shanxi Province, North China are investigated. Stems are relatively small, branch dichotomously, and possess a haplostele with metaxylem tracheids showing uniseriate scalariform thickenings. Protoxylem groups are associated with the forming of the petiolar trace, and a parenchyma plate appears in the process of separating petiolar traces. The cortex consists of three parts, with inner and middle parenchymatous zones and an outer sclerenchymatous zone. Stems are radially organized and bear helically arranged petioles. Petioles extend from the stems in various orientations while adventitious roots extend through the cauline cortex perpendicular or oblique to the stem. Associated rachides are D-shaped in cross section and the xylem is slightly to conspicuously adaxially curved with 1 protoxylem ridge at each lateral margin. Differences with previously known genera of Botryopteridaceae lead to creation of new genus, Diodonopteris gracilis Ma et al. gen. nov. et sp. nov. that demonstrates features that overlap to some extent with those of previously known genera within Botryopteridaceae. The habit and growth forms of D. gracilis are considered. D. gracilis represents by far the best known plant of Botryopteridaceae recognized from the Cathaysian Flora.