The Calamarieae, now known to have been the chief Palaeozoic representatives of the Horsetail stock, attained the dimensions of trees, reaching, according to Grand' Eury, a height of from 30 to 60 metres, and showed in all respects a higher and more varied organization than their recent successors.
Different genera have been founded on leaf-bearing branches of Calamarieae; apart from Archaeocalamites, already mentioned, and Autophyllites (Grand' Eury), in both of which the leaves were dichotomous, we have Annularia, Asterophyllites and Calamocladus (in Grand' Eury's limited sense), with simple leaves.
In Asterophyllites., the generic distinction of which from Annularia is not always clear, the narrow linear leaves are in crowded whorls, and the ultimate branches distichously arranged; in the Calamocladus of Grand' Eury - characteristic of the Upper Coal Measures - the whorls are more remote, and the twigs polystichous in arrangement.
According to Grand' Eury, the Palaeostachya fructification was most commonly associated with Asterophyllites foliage.
Various other seeds of the same type are known, and in a great number of instances Grand' Eury has found the fronds of Neuropterideae (Medulloseae) in close association with definite species of seeds, so there can be little doubt that the whole family was seed-bearing.