Equisetopsida, or Sphenopsida, is a class of plants with a fossil record going back to the Devonian. Living species are commonly known as horsetails and typically grow in wet areas, with needle-like leaves radiating at regular intervals from a single vertical stem. Equisetopsida is placed in the botanical division of ferns (Pteridophyta), though sometimes regarded as a separate division Equisetophyta (also as Sphenophyta or Arthrophyta).
