[2] Once thought to be descendants of early vascular plants (the Psilophyta of the Devonian period), Psilotaceae have been shown by molecular phylogenetics to be ferns (Polypodiopsida), and a sister group of the Ophioglossaceae.

The small, stem-like gametophytes of Psilotaceae are located in this rhizome system, and they aid in a plant's nutrient absorption through the soil.

The sporangia of Psilotaceae are fused together into small and distinctive yellow balls called synangia (shown in the picture of P. nudum above).

In the molecular phylogenetic classification of Smith et al. in 2006, Psilotales, containing the single family Psilotaceae comprising Psilotum and Tmesipteris, was placed with the order Ophioglossales in the class Psilotopsida.

[3] The linear sequence of Christenhusz et al. (2011), intended for compatibility with the classification of Chase and Reveal (2009)[4] which placed all land plants in Equisetopsida,[5] made it a member of subclass Ophioglossidae, equivalent to Smith's Psilotopsida.