Annularia

Annularia is a form taxon, applied to fossil foliage belonging to extinct plants of the genus Calamites in the order Equisetales.

Description
Annularia is a form taxon name given to leaves of Calamites. In that species, the leaves formed radiating leaf whorls at each stem node, in a similar way to the branches of Equisetum, an extant genus of horsetails. Annularia leaves are arranged in whorls of between 8-13 leaves. The leaf shape is quite variable, being oval in Annularia sphenophylloides and linear to lanceolate in Annularia radiata, but they are always flat and of varying lengths.

Calamites were arborescent and grew to a height of 32 ft.

Fossil records
Fossils of this genus have been discovered in the Permian strata of Russia and in the Carboniferous (around ) strata of the United States, Canada, China and Europe.