''Tetracentron'' is a genus of

flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Ancient Greek, Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed with ...

with a sole living species being '' Tetracentron sinense'' and several extinct species. It was formerly considered the sole genus in the family Tetracentraceae, though it is now included 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 ...

together with the genus ''

Trochodendron ''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 ...

''.

Range

The living '' Tetracentron sinense'' is native to southern

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

and the eastern

Himalaya The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than 100 pea ...

, where it grows at altitudes of in a temperate climate; it has no widely used common name in English, though is sometimes called "spur-leaf".

Wood vessels

''Tetracentron'' shares with ''Trochodendron'' the feature, very unusual in

angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed within a fruit. T ...

, of lacking

vessel element A vessel element or vessel member (also called a xylem vessel) is one of the cell types found in xylem, the water conducting tissue of plants. Vessel elements are found in most angiosperms (flowering plants) and in some gymnosperms such as cyca ...

s in its

wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

. 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, research in

Molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

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 disc ...

and others has shown that these two genera are not

basal angiosperms The basal angiosperms are the flowering plants which diverged from the lineage leading to most flowering plants. In particular, the most basal angiosperms were called the ANITA grade, which is made up of ''Amborella'' (a single species of shrub f ...

, but basal eudicots.Andreas Worberg, Dietmar Quandt, Anna-Magdalena Barniske, Cornelia Löhne, Khidir W. Hilu, and Thomas Borsch. 2007. "Phylogeny of basal eudicots: Insights from non-coding and rapidly evolving DNA." ''Organisms Diversity and Evolution'' 7(1):55-77. (see "External links" below). This suggests that the absence of vessel elements is a secondarily evolved character, not a primitive one.

Fossil record

The fossil record, extending back to the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

, shows a much wider distribution than modern times. Fossils of this genus have been found in

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

, Canada,;

Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...

Washington state Washington, officially the State of Washington, is a state in the Pacific Northwest region of the United States. It is often referred to as Washington State to distinguish it from the national capital, both named after George Washington ...

, United States; and

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

. The

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

'' Tetracentron atlanticum'', described in 2008, is the first confirmed record of the genus in Europe. This species was described from pollen, fruits, and leaves found in Iceland. Specimens from British Columbia and Washington state are found in a series of Eocene Lakes in the

Okanagan Highland The Okanagan Highland is an elevated hilly plateau area in British Columbia, Canada, and the U.S. state of Washington (where it is spelled Okanogan Highlands). Rounded mountains with elevations up to above sea level and deep, narrow valleys ar ...

s region in association with several extinct ''Trochodendron'' species. The

Paleogene The Paleogene Period ( ; also spelled Palaeogene or Palæogene) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period Ma (million years ago) to the beginning of the Neogene Period Ma. It is the fir ...

species ''Tetracentron piperoides'' from Alaska is currently regarded as suspect due to the lack of associated fruits.

Species

*†'' Tetracentron atlanticum'' (Miocene, Iceland) *†'' Tetracentron hopkinsii'' (Ypresian,

Allenby Formation The Allenby formation is a sedimentary rock formation in British Columbia which was deposited during the Ypresian stage of the Early Eocene. It consists of conglomerates, sandstones with interbedded shales and coal. The shales contain an ...

, British Columbia;

Klondike Mountain Formation The Klondike Mountain Formation is an Early Eocene (Ypresian) geological formation located in the northeast central area of Washington (state), Washington state. The formation is composed of volcanic rocks in the upper unit and volcanic plus lacu ...

, Washington state) *†''

Tetracentron piperoides ''Tetracentron'' is a genus of flowering plant with a sole living species being '' Tetracentron sinense'' and several extinct species. It was formerly considered the sole genus in the family Tetracentraceae, though it is now included in the fami ...

'' *†'' Tetracentron remberi'' (Miocene, Clarkia, Idaho) *'' Tetracentron sinense''

References

External links

*Flora of China
''Tetracentron''
an
Tetracentraceae
{{Taxonbar, from=Q18330754 Eudicot genera Trochodendrales Taxa named by Daniel Oliver