The zosterophylls were among the first vascular plants in the fossil record, and share an ancestor with the living lycophytes.

Hao and Xue in 2013 used the presence or absence of terminal sporangia as a major dividing feature.

[2] Hao and Xue consider the order Gosslingiales to be one of the two major divisions of the zosterophylls (class Zosterophyllopsida).

[6] The classification of the zoterophylls is unsettled; Edwards and coauthors commented in 2015 that in the almost 50 years since 1966, "there has been an extraordinary proliferation of information on [...] new taxa, many of them endemics that reveal combinations of characters that defy conventional classification".

However, a study of zosterophyll diversity over time showed that the proportion of taxa with terminal sporangia declined in the Late Lochkovian when taxa without terminal sporangia evolved.