''Thursophyton'' ("plant from
Thurso
Thurso (pronounced ; , ) is a town and former burgh on the north coast of the Highland council area of Scotland. Situated in the historical County of Caithness, it is the northernmost town on the island of Great Britain. From a latitudinal s ...
") is a
form genus
Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of sc ...
of
extinct
Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
vascular plants known from anatomically preserved specimens originally described from the
Givetian
The Givetian is one of two faunal stages in the Middle Devonian Period. It lasted from million years ago to million years ago. It was preceded by the Eifelian Stage and followed by the Frasnian Stage. It is named after the town of Givet in ...
(
Middle Devonian
In the geological timescale, the Middle Devonian epoch (from 393.3 ± 1.2 million years ago to 382.7 ± 1.6 million years ago) occurred during the Devonian period, after the end of the Emsian age.
The Middle Devonian epoch is subdivided into two ...
) of Scotland, and since reported from other parts of northern Europe.
The taxonomic position of ''Thursophyton'' has been uncertain; most authors have considered it too imperfectly known to place, or have assigned it to the
Lycopodiophyta
The lycophytes, when broadly circumscribed, are a group of vascular plants that include the clubmosses. They are sometimes placed in a division Lycopodiophyta or Lycophyta or in a subdivision Lycopodiophytina. They are one of the oldest lineag ...
. Unpublished research suggests similarities with spiny
genera
Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
of the
Zosterophyllopsida.
Description
''Thursophyton'' is a genus of terrestrial
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 which flourished in the Middle
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 ...
period. These plants consisted of aerial stems branching dichotomously, trichotomously or pseudomonopodially, at least the main axes clothed in spirally arranged spines up to 7 mm long, which are not leaves as they are not vascularised and leave no scar when removed.
The stems contain an elliptical exarch
xylem
Xylem is one of the two types of transport tissue (biology), tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts o ...
having both annular and spirally thickened tracheids; very little is known about the sporangia.
Species
The
type species
In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
is ''Thursophyton milleri''. Other species have been suggested (e.g. ''T. reidii'', ''T. eberfeldense'', ''T. hostimense'', ''T. vahlbergianum'') which are usually regarded as synonyms of ''T. milleri''. Because of the poor preservation of much of this plant material from the Devonian period, it is likely that other synonyms exist e.g. ''Euthursophyton hamperbachense'' Mustafa from Germany.
See also
*
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 ...
References
{{Taxonbar, from=Q55635826
Middle Devonian plants
Prehistoric plant genera