Equisetum, pictured at right, is the only living genus in the Equisetaceae. This genus, with about thirty living species, is divided into two sections, Equisetum and Hippochaete, based on the presence or absence of regular whorls of branches. Equisetum arvense, a common North American species, is pictured here.
The Equisetaceae have been around since the Permian, and comprised a moderately diverse group in the Late Permian and Triassic. Most fossils in the Equisetaceae are classified in the form genus Equisetites or in the living genus Equisetum.
The Equisetaceae are the only surviving lineage of sphenopsids.