Ophioglossaceae, the adder's-tongue family, is a family of ferns (though some studies have instead suggested a closer relationship to angiosperms), 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), with a total of ca 80 known species. A broad definition of the family and its genera have been taken in several recen