Ophioglossaceae, the adder's-tongue family, is a family of
ferns, currently thought to be most closely related to
Psilotaceae, the two together comprising the class
Psilotopsida as the
sibling group to the rest of the ferns. The Ophioglossaceae is one of two groups of ferns traditionally known as
eusporangiate ferns. The number of
genera included in the family varies between different authors' treatments, and most conservatively the family is treated as containing four genera,
Ophioglossum,
Botrychium,
Helminthostachys, and
Mankyua (placed in two to four separate families in other treatments). A broad definition of the family and its genera have been taken in several recent treatments. A notable exception is the classification of Kato, who advocated the division of
Botrychium into four genera:
Botrychium s.s.,
Sceptridium,
Japanobotrychium, and
Botrypus.
