Annularia is a form taxon, applied to fossil foliage belonging to extinct plants of the genus Calamites in the order Equisetales.
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.[1]
Calamites were arborescent and grew to a height of 32abbr=offNaNabbr=off.[2]
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.[1] [3]