1) Family equisetaceae 2) Fern family 3) Horsetail family 
== Evolution and systematics == 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 orde...
(from the article `Sphenophyta`) ...leaves; 2 families: Sphenophyllaceae and Cheirostrobaceae.Order EquisetalesTwo families: Calamitaceae, extinct tree horsetails; and Equisetaceae, ...
[n] - sole surviving family of the Equisetales: fern allies
family Equisetaceae noun sole surviving family of the Equisetales: fern allies