Growth architecture and microsporangiate strobilus of Sublepidodendron grabaui (Lycopsida) from the Late Devonian of South China

• Sublepidodendron grabaui possesses pseudomonopodial axes.
• The monosporangiate nature of Sublepidodendron grabaui is confirmed.
• The microsporangiate strobilus contains Lycospora granulata Group microspores.
• The Lycospora granulata Group microspores can occur in monosporangiate strobili.

The arborescent lycopsid Sublepidodendron grabaui was widely distributed in the Late Devonian of South China. Its morphology and anatomy have been described, but the microsporangiate strobilus remains unclear. New material collected from the Guanshan Member of the Wutong Formation in Zhejiang Province allowed us to provide more details of this plant. The pseudomonopodial axis without secondary xylem bears medullated stele and branch traces arranged in irregular helices. The lateral branch possesses solid exarch primary xylem. This pseudomonopodial branching system possibly represents the crown or cauline lateral branch. The microsporangiate strobilus contains microspores belonging to the Lycospora granulata Group. The monosporangiate nature of S. grabaui is confirmed, and the classification of Sublepidodendraceae into the suborder Dichostrobiles is supported. The L. granulata Group microspores are suggested to occur not only in bisporangiate strobili but also in monosporangiate strobili.