Trimerophytopsida (or Trimeropsida) is a

class Class, Classes, 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 d ...

of early

vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...

s from the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

, informally called trimerophytes. It contains genera such as '' Psilophyton''. This group is probably

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

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

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

s and seed plants evolved. Different authors have treated the group at different

taxonomic rank In biology, taxonomic rank (which some authors prefer to call nomenclatural rank because ranking is part of nomenclature rather than taxonomy proper, according to some definitions of these terms) is the relative or absolute level of a group of or ...

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 polysporangiophytes) 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

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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 Rush ...

; he clarified his proposal in 1975. One of the three groups was the Trimerophytina. The subdivision is based on the

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...

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 or ICNafp) 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 tho ...

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