关键词: 亚鳞木属, 水韭目(广义), 木本石松植物, 分支系统学

Abstract: Sublepidodendron (Nathorst) Hirmer is considered one of the index plant megafossils in the Late Devonian of China. Historically, this genus lacks an indispensable study on its biological characters, so its taxonomy has long been a debatable subject, which hinders a true appreciation of this generic systematic position and of evolutionary lineages within the lycopsids. The present cladistic study suggests that Sublepidodendron possesses many similar synapomorphies to those phylogenetically more advanced genera in the families Sigillariaceae, Lepidodendraceae and Diaphorodendraceae rather than the order Protolepidodendrales as formerly thought. Thus, the authors present a new taxonomical system for Sublepidodendron, which is referred to the family Sublepidodendraceae, and assigned in turn to the order Isoёtales sensu lato. In the authors cladogram, Sublepidodendraceae is phylogenetically bridging between the families Leptophloeaceae and Sigillariaceae rather than constituting any sister groups with one of members in the order Protolepidodendrales. The cladistic pattern reveals that the Carboniferous more advanced arborescent lycopsids must have evolved by the Late Devonian (Famennian) rather than precipitately occurred in the Carboniferous. Sublepidodendron may represent one of the members of the phylogenetically more advancedarborescent lycopsids or one of the ancestral groups to the families Lepidodendraceae or Diaphorodendraceae.

Key words: Sublepidodendron, Isoёtales sensu lato, arborescent lycopsid, cladistics