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

摘要： 亚鳞木属被视为中国晚泥盆世的标志性植物大化石之一。分支系统学研究表明，亚鳞木属不宜归入传统所认为的原始鳞木目，因为它与系统发育上进化的封印木科、鳞木科和奇木科中成员的近共裔性状相似。作者提出该属的新分类系统：亚鳞木属隶属于亚鳞木科，归入广义的水韭目。在当前的分支图中，亚鳞木科的系统发育位置处于封印木科和薄皮木科之间，这种分支式样表明系统发育上比较进化的木本石松植物并不是在石炭纪突然出现的，而是在晚泥盆世（法门期）就已经演化。亚鳞木属可能代表了系统发育上比较高级的木本石松的成员或鳞木科 (或奇木科) 的祖先类群之一。

关键词: 亚鳞木属, 水韭目(广义), 木本石松植物, 分支系统学