''Trochodendron'' is a genus of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

s with one living species, ''

Trochodendron aralioides ''Trochodendron aralioides'', sometimes colloquially called wheel tree, is a flowering plant and the sole living species in the genus ''Trochodendron'', which also includes several extinct species. It was also often considered the sole species in ...

'', and six extinct species known from the fossil record. It was often considered the sole genus in the family

Trochodendraceae Trochodendraceae is the only family of flowering plants in the order Trochodendrales. It comprises two extant genera, each with a single species along with up to five additional extinct genera and a number of extinct species. The living specie ...

, though botanists now also include the distinct genus '' Tetracentron'' in the family.

Species

* ''

'' *†''

Trochodendron beckii ''Trochodendron'' is a genus of flowering plants with one living species, ''Trochodendron aralioides'', and six extinct species known from the fossil record. It was often considered the sole genus in the family Trochodendraceae, though botanists ...

'' *†'' Trochodendron drachukii'' (Infructescence; Ypresian,

McAbee Fossil Beds The McAbee Fossil Beds is a Heritage Site that protects an Eocene Epoch fossil locality east of Cache Creek, British Columbia, Canada, just north of and visible from Provincial Highway 97 / the Trans-Canada Highway ( Highway 1). The McAbee Fos ...

, British Columbia) *†'' Trochodendron evenense'' (Leaves; Miocene, Kamchatka) *†''

Trochodendron infernense ''Trochodendron'' is a genus of flowering plants with one living species, ''Trochodendron aralioides'', and six extinct species known from the fossil record. It was often considered the sole genus in the family Trochodendraceae, though botanists ...

'' (Infructescence; Late Palaeocene,

Fort Union Formation The Fort Union Formation is a geologic unit containing sandstones, shales, and coal beds in Wyoming, Montana, and parts of adjacent states. In the Powder River Basin, it contains important economic deposits of coal, uranium, and coalbed methane. ...

) *†''

Trochodendron kamtschaticum ''Trochodendron'' is a genus of flowering plants with one living species, ''Trochodendron aralioides'', and six extinct species known from the fossil record. It was often considered the sole genus in the family Trochodendraceae, though botanists ...

'' (Infructescence; Miocene, Kamchatka) *†''

Trochodendron nastae ''Trochodendron nastae'' is an extinct species of flowering plant in the family Trochodendraceae known from fossil leaves found in the early Eocene Ypresian stage Klondike Mountain Formation deposits of northern Washington state. ''T. nastae'' i ...

'' (Leaves; Ypresian,

Klondike Mountain Formation The Klondike Mountain Formation is an Early Eocene (Ypresian) geological formation located in the northeast central area of Washington state. The formation, named for the type location designated in 1962, Klondike Mountain north of Republic, Wash ...

, Washington state) *†'' Trochodendron postnastae'' (Leaves; Langhian, Moose Mountain Flora, Oregon) *†''

Trochodendron protoaralioides ''Trochodendron'' is a genus of flowering plants with one living species, ''Trochodendron aralioides'', and six extinct species known from the fossil record. It was often considered the sole genus in the family Trochodendraceae, though botanists ...

'' (Leaves; late Miocene, Japan) *†''

Trochodendron rosayi ''Trochodendron rosayi'' is an extinct species of flowering plant in the family Trochodendraceae. The species is known from fossils found in Middle Miocene deposits of central Oregon. ''T. rosayi'' are possibly the fruits belonging to the extin ...

'' (Infructescence; Langhian, Moose Mountain Flora, Oregon) ''Trochodendron'' is native to

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

, southern

Korea Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic o ...

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia, at the junction of the East and South China Seas in the northwestern Pacific Ocean, with the People's Republic of China (PRC) to the northwest, Japan to the nort ...

and the

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Taiwan: the Ōsumi, Tokara, Amami, Okinawa, and Sakishima Islands (further divided into the Miyako and Yaeyama Islands), with Yonaguni ...

, with fossils known from

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

, and the Russian Far East. ''Trochodendron aralioides'' is an

evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which ...

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

or large

shrub A shrub (often also called a bush) is a small-to-medium-sized perennial woody plant. Unlike herbaceous plants, shrubs have persistent woody stems above the ground. Shrubs can be either deciduous or evergreen. They are distinguished from trees ...

growing to 20 m tall. ''Trochodendron'' and ''Tetracentron'' lack

vessel element A vessel element or vessel member (also called trachea or xylem vessel) is one of the cell types found in xylem, the water conducting tissue of plants. Vessel elements are typically found in angiosperms (flowering plants) but absent from most gy ...

s in their

wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...

, a quite unusual feature in

angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants th ...

. This has long been considered a very primitive character, resulting in the classification of these two genera in a basal position in the angiosperms; however, genetic research by the

Angiosperm Phylogeny Group The Angiosperm Phylogeny Group (APG) is an informal international group of systematic botanists who collaborate to establish a consensus on the taxonomy of flowering plants (angiosperms) that reflects new knowledge about plant relationships disco ...

has shown it to be in a less basal position (early in the

eudicot The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons. Traditionally they were called tricolpates or non-magnoliid dicot ...

s), suggesting the absence of vessel elements in these two genera is a secondarily evolved character, not a primitive one.

Fossil record

Among the middle

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

Sarmatian The Sarmatians (; grc, Σαρμαται, Sarmatai; Latin: ) were a large confederation of Ancient Iranian peoples, ancient Eastern Iranian languages, Eastern Iranian peoples, Iranian Eurasian nomads, equestrian nomadic peoples of classical ant ...

palynoflora from the

Lavanttal The Lavant Valley (german: Lavanttal, sl, Labotska dolinaGams, Ivan. 1992. "Labotska dolina." ''Enciklopedija Slovenije'', vol. 6. Ljubljana: Mladinska knjiga, pp. 87–87. or ''Laboška dolina''; Southern Bavarian: ''Lovnthol'') lies in the Lav ...

Basin

Austria Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...

researchers have recognized ''Trochodendron''

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

pollen Pollen is a powdery substance produced by seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects the gametophyt ...

. The sediment containing the ''Trochodendron'' fossil pollen had accumulated in a lowland wetland environment with various vegetation units of mixed evergreen/deciduous broadleaved/conifer forests surrounding the wetland basin. Key relatives of the fossil taxa found with ''Trochodendron'' pollen are presently confined to humid warm temperate environments, suggesting a

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Geographical z ...

climate during the middle Miocene in Austria.

References

External links

Flora of China: ''Trochodendron''

i
L. Watson and M.J. Dallwitz (1992 onwards). The families of flowering plants.
{{Taxonbar, from=Q1857662 Eudicot genera Trochodendrales