Any member of a clade containing seed plants, ferns, horsetails, and their allies—i.e. all vascular land plants except the clubmosses and their relatives. Modern euphyllophytes are characterized by possessing true leaves (megaphylls) and branching stems of unequal length (‘overtopping’). In ancestral members the evolution of overtopping led to forms having a main axis with lateral branches. According to the telome theory, megaphylls subsequently evolved through infilling by photosynthetic tissue of spaces between the twigs of lateral shoots. Fossil evidence shows the first megaphylls appeared in the Devonian period. See also monilophyte.