Trochodendron nastae
Encyclopedia
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 is one of the oldest members of the genus Trochodendron
, which includes the living species T. aralioides
, native to Japan
, southern Korea
and Taiwan
and the coeval extinct species T. drachuckii
from Cache Creek, British Columbia
.
Description of the new species by Dr. Kathleen Pigg, Wesley Wehr, and Stephanie Ickert-Bond was based on the study of 11 complete and 55 partial compression fossil
specimens with the holotype
specimen, number "SR 98-02-01", being housed in the Stonerose Interpretive Center
, Republic, Washington
. They published their 2001 type description of the species in the International Journal of Plant Sciences volume number 162. and named the species nastae in honor of Charlotte G. Nast for her work on extinct and living members of the Trochodendrales.
T. nastae has been placed in the genus Trochodendron based on the overall shape of the leaves, the secondary vein structure, which forms weak chevrons bracing primary veins, and the tertiary veins forming four to five sided cells. However the primary veins are palmate in structure for T.nastae rather than being pinnate
as in T. aralioides.
Trochodendron shares with Tetracentron the very unusual feature in angiosperms
, of lacking vessel element
s in its wood
. 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
has shown it to be in a less basal position (early in the eudicots), suggesting that the absence of vessel elements is a secondarily evolved character, not a primitive one.
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
in the family Trochodendraceae
Trochodendraceae
Trochodendraceae is a family of flowering plants with two living genera found in southeast Asia. The two living species share the feature of secondary xylem without vessels, which is quite rare in angiosperms...
known from fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
leaves found in the early Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
Ypresian
Ypresian
In the geologic timescale the Ypresian is the oldest age or lowest stratigraphic stage of the Eocene. It spans the time between and , is preceded by the Thanetian age and is followed by the Eocene Lutetian age....
stage Klondike Mountain Formation
Klondike Mountain Formation
The Klondike Mountain Formation is an early Eocene geologic formation that records the sedimentation in the southern most of a string of highland subtropical/Temperate lakes in Washington state and British Columbia. The formation is best known for exceptionally well preserved plant and insect fossils...
deposits of Northern Washington State. T. nastae is one of the oldest members of the genus Trochodendron
Trochodendron
Trochodendron is a genus of flowering plants with one living species, Trochodendron aralioides, and six extinct species known from the fossil record...
, which includes the living species T. aralioides
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 the family Trochodendraceae, though botanists now include...
, native to Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, southern Korea
Korea
Korea ) is an East Asian geographic region that is currently divided into two separate sovereign states — North Korea and South Korea. Located on the Korean Peninsula, Korea is bordered by the People's Republic of China to the northwest, Russia to the northeast, and is separated from Japan to the...
and Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
and the coeval extinct species T. drachuckii
Trochodendron drachuckii
Trochodendron drachukii is an extinct species of flowering plant in the family Trochodendraceae known from a fossil fruiting structure found in the early Ypresian age Eocene fossils found in British Columbia, Canada. T. drachukii is one of the oldest members of the genus Trochodendron, which...
from Cache Creek, British Columbia
Cache Creek, British Columbia
Cache Creek is a junction community northeast of Vancouver in British Columbia, Canada. It is on the Trans-Canada Highway in the province of British Columbia at its junction with northbound Highway 97...
.
Description of the new species by Dr. Kathleen Pigg, Wesley Wehr, and Stephanie Ickert-Bond was based on the study of 11 complete and 55 partial compression fossil
Compression fossil
A compression fossil is a fossil preserved in sedimentary rock that has undergone physical compression. While it is uncommon to find animals preserved as good compression fossils, it is very common to find plants preserved this way...
specimens with the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen, number "SR 98-02-01", being housed in the Stonerose Interpretive Center
Stonerose Interpretive Center and Fossil Site
Established in 1989, the Stonerose Interpretive Center and Fossil Site is an Eocene Epoch fossil site and accompanying interpretive center, located in Republic, Washington, part of the Okanagan Highland. The fossils are from organisms that lived in the area nearly 50 million years ago when the area...
, Republic, Washington
Republic, Washington
Republic is a city in Ferry County, Washington, United States. The population was 1,073 at the 2010 census, a 12.5% increase over the 2000 Census. It is the county seat of Ferry County.-History:...
. They published their 2001 type description of the species in the International Journal of Plant Sciences volume number 162. and named the species nastae in honor of Charlotte G. Nast for her work on extinct and living members of the Trochodendrales.
T. nastae has been placed in the genus Trochodendron based on the overall shape of the leaves, the secondary vein structure, which forms weak chevrons bracing primary veins, and the tertiary veins forming four to five sided cells. However the primary veins are palmate in structure for T.nastae rather than being pinnate
Pinnate
Pinnate is a term used to describe feather-like or multi-divided features arising from both sides of a common axis in plant or animal structures, and comes from the Latin word pinna meaning "feather", "wing", or "fin". A similar term is pectinate, which refers to a comb-like arrangement of parts...
as in T. aralioides.
Trochodendron shares with Tetracentron the very unusual feature in angiosperms
Flowering plant
The flowering plants , also known as Angiospermae or Magnoliophyta, are the most diverse group of land plants. Angiosperms are seed-producing plants like the gymnosperms and can be distinguished from the gymnosperms by a series of synapomorphies...
, of lacking vessel element
Vessel element
A vessel element is one of the cell types found in xylem, the water conducting tissue of plants. Vessel elements are typically found in the angiosperms but absent from most gymnosperms such as the conifers....
s in its wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
. 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
Angiosperm Phylogeny Group
The Angiosperm Phylogeny Group, or APG, refers to an informal international group of systematic botanists who came together to try to establish a consensus on the taxonomy of flowering plants that would reflect new knowledge about plant relationships discovered through phylogenetic studies., three...
has shown it to be in a less basal position (early in the eudicots), suggesting that the absence of vessel elements is a secondarily evolved character, not a primitive one.