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 ...
of
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 ''
'' 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 Banks 1975; Psilophytopsida Kidston & Lang 1917; Psilophytidae Nemejc 1963">rimeropsida Banks 1975; Psilophytopsida Kidston & Lang 1917; Psilophytidae Nemejc 1963*** Order †Trimerophytales
Banks ex Kasper et al. 1974 Pia 1924">silophytales Pia 1924**** Family †Trimerophytaceae
Banks 1967 Hirmer 1927; Hostinellaceae Pia 1924; Dawsonitaceae Nemejc 1963">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 †''
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 ...
''
Dawson 1859 emend. Hueber & Banks 1967
***** Genus †''
Trimerophyton''
Hopping 1956
See also
*
Euphyllophyta
The euphyllophytes are a clade of plants within the tracheophytes (the vascular plants). The group may be treated as an unranked clade, a division under the name Euphyllophyta or a subdivision under the name Euphyllophytina. The euphyllophytes ...
, containing seed plants and ferns
References
Bibliography
*
{{Taxonbar, from=Q1816123
Devonian plants
Devonian first appearances
Devonian extinctions