Trimerophytopsida (or Trimeropsida) is a

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

of early

vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They al ...

s from the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

, informally called trimerophytes. It contains genera such as ''

Psilophyton ''Psilophyton'' is a genus (biology), genus of extinct vascular plants. Described in 1859, it was one of the first fossil plants to be found which was of Devonian age (about ). Specimens have been found in northern Maine, USA; Gaspé Bay, Queb ...

''. This group is probably

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

, and is believed to be the ancestral group from which both the

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

s and

seed plants A spermatophyte (; ), also known as phanerogam (taxon Phanerogamae) or phaenogam (taxon Phaenogamae), is any plant that produces seeds, hence the alternative name seed plant. Spermatophytes are a subset of the embryophytes or land plants. They inc ...

evolved. Different authors have treated the group at different

taxonomic rank In biological classification, taxonomic rank is the relative level of a group of organisms (a taxon) in an ancestral or hereditary hierarchy. A common system consists of species, genus, family (biology), family, order (biology), order, class (b ...

s using the names Trimerophyta, Trimerophytophyta, Trimerophytina, Trimerophytophytina and Trimerophytales.

Taxonomy

At first most of the early land plants other than the bryophytes (i.e. the

polysporangiophyte Polysporangiophytes, also called polysporangiates or formally Polysporangiophyta, are plants in which the spore-bearing generation (sporophyte) has branching stems (axes) that bear sporangia. The name literally means 'many sporangia plant'. The cl ...

s) were placed in a single class Psilophyta, established in 1917 by Kidston and Lang. As additional fossils were discovered and described, it became apparent that the Psilophyta were not a homogeneous group of plants. In 1968 Banks first proposed splitting this taxon into three groups, which he put at the

rank Rank is the relative position, value, worth, complexity, power, importance, authority, level, etc. of a person or object within a ranking, such as: Level or position in a hierarchical organization * Academic rank * Diplomatic rank * Hierarchy * H ...

subdivision Subdivision may refer to: Arts and entertainment * Subdivision (metre), in music * ''Subdivision'' (film), 2009 * "Subdivision", an episode of ''Prison Break'' (season 2) * ''Subdivisions'' (EP), by Sinch, 2005 * "Subdivisions" (song), by Rus ...

; he clarified his proposal in 1975. One of the three groups was the Trimerophytina. The subdivision is based on the type genus ''Trimerophyton'', which might be expected to produce 'Trimerophytophytina' as the name of the subdivision, but the ''

International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...

'' allows the 'phyton' part of a genus name optionally to be omitted before '-ophyta', '-ophytina' and '-opsida'. The group has also since been treated as a division under the name Trimerophyta, p. 227 or Trimerophytophyta, as a class under the name Trimeropsida or Trimerophytopsida (as here), and as an order under the name Trimerophytales. * Subphylum †Trimerophytina Banks 1975 ** Class †Trimerophytopsida Foster & Gifford 1974 rimeropsida Banks 1975; Psilophytopsida Kidston & Lang 1917; Psilophytidae Nemejc 1963*** Order †Trimerophytales Banks ex Kasper et al. 1974 silophytales Pia 1924**** Family †Trimerophytaceae Banks 1967 silophytaceae Hirmer 1927; Hostinellaceae Pia 1924; Dawsonitaceae Nemejc 1963***** Genus †'' Dawsonites'' Nemejc 1963 ***** Genus †''

Hostinella ''Hostinella'' is a form genus, used for bare dichotomously branching stems (axes) which have not been found in association with spore-forming organs or sporangia and so cannot be assigned to a more precise genus or species. Specimens assigned t ...

'' Barrande ex Stur 1882 ***** Genus †'' Oocampsa'' Andrews, Gensel & Kasper 1975 ***** Genus †'' Euphyllophyton'' Hao & Beck ***** Genus †'' Pauthecophyton'' Xue et al. 2012 ***** Genus †''

'' Dawson 1859 emend. Hueber & Banks 1967 ***** Genus †'' Trimerophyton'' Hopping 1956

References

Bibliography

* {{Taxonbar, from=Q1816123 Devonian plants Devonian first appearances Devonian extinctions

Taxonomy

See also

References

Bibliography