They first appeared in late Middle Pennsylvanian (Moscovian) times, 306.5–311.7 million years ago (Ma) in the tropical coal forests of Euramerica, and became an important component of Late Pennsylvanian (Kasimovian-Gzhelian; 299.0–306.5 Ma) vegetation of clastic soils and some peat soils.

[2] The relatively slender stems (fossil genus Callistophyton) had a eustele with a well-developed zone of secondary wood, and unlike most (but not all)[3] other Palaeozoic pteridosperms, showed axillary branching.

[2][5] The ovules were borne on the underside of pinnules that did not differ significantly in form from those of the purely vegetative fronds.

The pollen-producing organs (fossil genus Idanothekion) consisted of small, radially symmetrical synangia, with each pollen-sac having a longitudinal dehisence structure.

Occasional Vesicaspora pollen grains and fragments of Dicksonites-like fronds occur in early Moscovian (middle Westphalian) strata, especially in intra-montane basins.