Horneophytopsida

Horneophytopsida Temporal range:
Reconstruction of Horneophyton lignieri
Scientific classification
Kingdom:	Plantae
Clade:	Polysporangiophytes
Class:	†Horneophytopsida
Synonyms
Langiophytophyta Doweld 2001

Horneophytopsida is 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 (around 430 to 390 million years ago). They are the simplest known polysporangiophytes, i.e. plants with sporophytes bearing many spore-forming organs (sporangia) 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.

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 (in particular did not have tracheids), although its conducting tissue is more complex than that of the Horneophytopsida.

Phylogeny

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

polysporangiophytes	Aglaophyton Tracheophyta Horneophytopsida Tortilicaulis Caia Horneophyton

(See the Polysporangiophyte article for the expanded cladogram.)

Taxonomy

• Phylum Horneophyta
  • Class Horneophytopsida Němejc 1960 [Horneophytidae Němejc 1963; Langiophytopsida Doweld 2001]
    • Order Horneophytales Němejc 1960 [Langiophytales Doweld 2001]
      • Family Horneophytaceae Němejc 1960 [Horneophytaceae Koidzumi 1939 nomen novum; Langiophytaceae Doweld 2001; Horneaceae Hirmer 1927; Pectinophytaceae Ananiev 1963]
        • Genus ?†Emphanisporites McGregor 1961 [form taxa- spores]
        • Genus ?†Salopella Edwards & Richardson 1974 [form taxa- stem; axis]
        • Genus ?†Tarrantia Fanning, Edwards & Richardson 1992 [form taxa- stem with sporangia]
        • Genus †Tortilicaulis Edwards 1979
        • Genus †Caia Fanning, Edwards & Richardson 1990
        • Genus †Horneophyton Barghoorn & Darrah 1938 [Hornea Kidston & Lang 1920 non Baker 1877; Langiophyton Remy et Hass 1991 form taxa- female gametophyte]

See also

• Polysporangiophytes

External links

• Horneophyton at the University of Aberdeen
• Cladogram from Crane, Herendeen & Friis 2004