See text Zosterophyllum was a genus of Silurian-Devonian vascular land plants with naked branching axes on which usually kidney-shaped sporangia were arranged in lateral positions.

It is the type genus for the group known as zosterophylls, thought to be part of the lineage from which modern lycophytes evolved.

Sporangia are grouped into a compact spike in which they are either helically arranged or form distinct rows (e.g. Z. llanoveranum).

[1] Hao and Xue in 2013 used the absence of terminal sporangia to place some species, such as Z. llanoveranum, in the paraphyletic order Gosslingiales, a group of zosterophylls considered to have indeterminate growth, with fertile branches generally showing circinate vernation (initially curled up).

[2] A cladogram published in 2004 by Crane et al. places the species of Zosterophyllum in a paraphyletic stem group of broadly defined "zosterophylls", basal to the lycopsids (living and extinct clubmosses and relatives).