[2] Equisetaceae is the only surviving family of the Equisetales, a group with many fossils of large tree-like plants that possessed ribbed stems similar to modern horsetails.

Pseudobornia is the oldest known relative of Equisetum; it grew in the late Devonian, about 375 million years ago and is assigned to its own order.

Equisetites is a "wastebin taxon" uniting all sorts of large horsetails from the Mesozoic; it is almost certainly paraphyletic and would probably warrant being subsumed in Equisetum.

Equicalastrobus is the name given to fossil horsetail strobili, which probably mostly or completely belong to the (sterile) plants placed in Equisetites.

[3] The earliest fossils that can be reliabily attributed to the Equisetaceae proper date to the Triassic.