A New Lycopsid from the Upper Devonian of Hubei Province, China

Abstract

A new herbaceous lycopsid, Hubeiia dicrofollia gen. et sp. nov., is described from the Xiejingsi Formation (Late Devonian) of Hubei Province, China. Its stems are isotomously dichotomized. Leaf bases are circular or slightly elliptical in shape and arranged in low helices or alternating pseudowhorls. Persistent leaves are divided into four segments as a result of two successive dichotomies. It has a solid exarch primary xylem strand. Protoxylem tracheids are composed of annular elements that appear as ridges on the stele surface. Metaxylem tracheids are scalariformly thickened and between thickened bars present vertical threads generally termed “Williamson’s striations.” Primary phloem forms a narrow band, four to eight cells thick, surrounding the stele. The cortex is relatively thick, possibly two zoned. Leaf traces are mesarch; they depart directly from protoxylem points and pass through the cortex with a stable oblique angle. This plant possesses a distinctive combination of characters, i.e., forked leaves in morphology and scalariformly thickened tracheids with Williamson’s striations in anatomy, and therefore it is designated as a new stem form genus Hubeiia gen. nov. Taxonomically, it is assigned to Protolepidodendraceae.