The late Silurian to Early Devonian floras in the South China Block provide important evidence for the radiation of early land plants, including the well-known Posongchong Formation and Xujiachong Formation of Yunnan Province and the Pingyipu Group of Sichuan Province. However, some taxa in these stratigraphic units are described on the basis of limited specimens, or even a single and/or poorly preserved specimen, and need further investigation. The re-investigation of specimen PB6458 from the Xujiachong Formation at the Xujiachong section near Xujiachong Village, Qujing City, Yunnan Province, which is the holotype of Zosterophyllum spathulatum Li and Cai, 1977, reveals some new characters of its strobilus, sporophylls, and sporangia and denies its assignment to Zosterophyllum Penhallow, 1892. Instead, this specimen should be assigned to Adoketophyton subverticillatum (Li and Cai) Li and Edwards, 1992. This taxonomic revision extends the paleogeographic distribution of Adoketophyton Li and Edwards, 1992 and further enhances this genus as one of the index fossils of Lower Devonian non-marine strata in the South China Block.