Article: A new homosporous, arborescent lycopsid from the Middle Devonian of Xinjiang, Northwest China

A new arborescent lycopsid, Hoxtolgaya robusta gen. et sp. nov., is described from the Middle Devonian of Xinjiang, Northwest China. It has stems up to 90 mm wide with fusiform leaf bases and long linear microphylls. Sporophylls are not aggregated into strobili and are isomorphic, with sporangia homosporous and bearing Acinosporites-type microspores. A syndrome of characters in Hoxtolgaya, including the arborescence and the homospory, implies that the arborescent habit is not necessarily correlated with the heterospory in the early evolution of arborescent lycopsids. Homosporous, arborescent lycopsids probably represent one of the transient forms between the Devonian herbaceous protolepidodendrids and the Devonian–Carboniferous heterosporous arborescent lycopsids.