''Equisetites'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 within

Equisetaceae Equisetaceae, also known as the horsetail family, is a family of ferns and the only surviving family of the order Equisetales, with one surviving genus, ''Equisetum'', comprising about twenty species. Evolution and systematics Equisetaceae is ...

, a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

s that reproduce by

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s rather than seeds. The genus was named by Sternberg (1833)K. Sternberg, von Graf. (1833). Versuch einer geognostisch-botanischen Darstellung der Flora der Vorwelt, Heft V. Prag (1833–1838) and contains at least 40 named species and two unnamed species, with the earliest known species being ''E. hemingwayi'' from the Westphalian of

Yorkshire Yorkshire ( ) is an area of Northern England which was History of Yorkshire, historically a county. Despite no longer being used for administration, Yorkshire retains a strong regional identity. The county was named after its county town, the ...

England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...

, though the affinity of this genus to modern Equistaceae is uncertain.

Systematics

''Equisetites'' is a "

wastebin taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the purpose of classifying organisms that do not fit anywhere else. They are typically defined by e ...

" uniting all sorts of large horsetails from the

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

; it is almost certainly

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 would probably warrant being subsumed in ''

Equisetum ''Equisetum'' (; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass Equisetidae, which ...

''. But while some of the species placed there are likely to be ancestral to the modern horsetails, there have been reports of

secondary growth In botany, secondary growth is the growth that results from cell division in the cambia or lateral meristems and that causes the stems and roots to thicken, while primary growth is growth that occurs as a result of cell division at the tips ...

in other ''Equisetites'', and these probably represent a distinct and now-extinct horsetail lineage. '' Equicalastrobus'' is the name given to fossil horsetail strobili, which probably mostly or completely belong to the (sterile) plants placed in ''Equisetites''. (2005): ''Equisetites aequecaliginosus'' sp. nov., ein Riesenschachtelhalm aus der spättriassischen Formation Santa Clara, Sonora, Mexiko 'Equisetites aequecaliginosus'' sp. nov., a tall horsetail from the Late Triassic Santa Clara Formation, Sonora, Mexico ''Revue de Paléobiologie'' 24(1): 331–364 erman with English abstractbr>PDf fulltext
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References

{{Taxonbar, from=Q3730927 Equisetales Fossil taxa described in 1833 Carboniferous plants Permian plants Triassic plants Jurassic plants Cretaceous plants Prehistoric plant genera