Horneophytopsida


The Horneophytopsida, informally called horneophytes, are a class of extinct plants which consisted of branched stems without leaves, true roots or vascular tissue, found from the Late Silurian to the Early Devonian. They are the simplest known polysporangiophytes, i.e. plants with sporophytes bearing many spore-forming organs on branched stems. They were formerly classified among the rhyniophytes, but it was later found that some of the original members of the group had simple vascular tissue and others did not. The group has also been treated as the division Horneophyta.
In 2004, Crane et al. published a cladogram for the polysporangiophytes in which the Horneophytopsida are shown as the sister group of all other polysporangiophytes. One other former rhyniophyte, Aglaophyton, is also placed outside the tracheophyte clade, as it did not possess true vascular tissue, although its conducting tissue is more complex than that of the Horneophytopsida.

Phylogeny

Partial cladogram by Crane, Herendeen & Friis 2004, with emphasis on horneophytes.

Genera

Genera that have been placed in the horneophytes include:
Other sources place only Horneophyton in this group, treating Caia and Tortilicaulis as actual or possible rhyniophytes.