Phylogenetic Relationships of the Zosterophylls and Lycopsids: Evidence from Morphology, Paleoecology, and Cladistic Methods of Inference

Zosterophylls have been considered the probable ancestors of lycopsids since the establishment of the group in 1968 by Banks. Both share the characters of exarch protosteles and reniform sporangia, and it is argued that characters separating the two, e.g., microphylls and leaf-associated sporangia, could easily be derived by modification of zosterophyll emergences and sporangial position. Recently, different opinions concerning the derivation of lycopsid features have been proposed and an earlier time of occurrence of lycopsids has been suggested (...)