Horneophyton is among the most abundant fossil organisms found in the Rhynie chert, a Devonian Lagerstätte in Aberdeenshire, UK.

[2] Early stages of development of the sporophytes of Horneophyton (as of hornworts) may have been dependent on their parent gametophytes for nutrition, but mature specimens have expanded, corm-like bases to their stems, up to 6 mm in diameter, that bore rhizoids and appear to be anchored in soil, suggesting a capacity for independent existence after the gametophyte had degenerated.

[9] First named by Kidston & Lang in 1920 from Early Devonian fossils in the Rhynie chert,[10] the original generic name Hornea was later found to already refer to a flowering plant in the family Sapindaceae, Hornea mauritiana, leading Barghoorn and Darrah to propose renaming the genus Horneophyton in 1938.

[1] It was classified as a rhyniophyte (subdivision Rhyniophytina) by Banks, but the absence of true vascular tissue led Kenrick and Crane in 1997 to create a new class, Horneophytopsida, for this and similar genera.

The free living nature of its sporophytes, and the fact that they branching repeatedly, are marked differences which force it into the stem group of tracheophytes (along with Aglaophyton).