Fructifications typically consist of strobili. Sphenophytes were widespread in the Carboniferous and Early Permian. Two major groups can be distinguished, the Calamitales and the Sphenophyllales. The calamites were rhizome-borne trees with secondary growth which could reach a height of up to 20 m.
Most species are indicative for humid to wet environments.
They often occurred in monotypic stands along the shorelines of lakes and rivers, probably comparable to modern reed vegetations. The name Calamites was originally given to pith casts of the hollow stems, but is now also used for the whole plant. Annularia and Asterophyllites are two types of calamite foliage. The only living sphenophyte is the modern Equisetum or horsetail. The genus has been established for the pith casts, the natural infillings of the hollow central parts of the stem.