''Eucommia montana'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

species 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 ...

in the family

Eucommiaceae ''Eucommia'' is a genus of small trees now native to China, with a fossil record that shows a much wider distribution. The single living species, ''Eucommia ulmoides'', is near threatened in the wild, but is widely cultivated in China for its ...

. ''E. montana'' is known from

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 ...

fruits found in

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

deposits of the northwestern United States southeastern

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

south to

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

and east to

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

and

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

. ''E. montana'' is one of five described fossil species from North America assigned to the modern genus ''

Eucommia ''Eucommia'' is a genus of small trees now native to China, with a fossil record that shows a much wider distribution. The single living species, ''Eucommia ulmoides'', is near threatened in the wild, but is widely cultivated in China for its ...

''. The other species are '' E. constans'', '' E. eocenica'', '' E. jeffersonensis'', and '' E. rowlandii''.

History and classification

''Eucommia montana'' was first described by Roland W. Brown in 1940 from the late Eocene Renova Formation which outcrops near Grant in

Beaverhead County, Montana Beaverhead County is the largest county by area in the U.S. state of Montana. As of the 2020 census, the population was 9,371. Its county seat is Dillon. The county was founded in 1865. Much of the perimeter of the county is the Continental Di ...

. Further collecting in outcrops of Passamari Formation in the Ruby River Basin of southwestern Montana lead to the description of another species, ''Eucommia brownii'' by Herman F. Becker in 1960. This was based on an apparent smaller size to the fruits found in the Passamari formation. However, further collecting in the 1960s showed a range of size greater than first thought and led to Becker reassigning the fossils to ''E. montana'' in 1969. The Fossils were again examined in 1997 by paleobotanists Victor Call and David Dilcher, both of the

University of Florida The University of Florida (Florida or UF) is a public land-grant research university in Gainesville, Florida. It is a senior member of the State University System of Florida, traces its origins to 1853, and has operated continuously on its ...

in Gainesville. In the reassessment of the species, Call and Dilcher expanded both the

chronostratigraphic Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geologic ...

and geographic range for the species by assigning a number of fossils from locations across western North America to ''E. montana''. In addition to the Ruby basin and Grant fossils, fossils from middle Eocene rocks in the Beaverhead Basins of Beaverhead County (Montana) were assigned to ''E. montana''. The western most occurrence of the species is found in the

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

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 ...

of Northern

Washington state Washington (), officially the State of Washington, is a state in the Pacific Northwest region of the Western United States. Named for George Washington—the first U.S. president—the state was formed from the western part of the Washington ...

. The slightly younger

Coldwater Beds The Coldwater Beds are a geologic formation of the Okanagan Highlands in British Columbia, Canada. They preserve fossils dating back to the Ypresian stage of the Eocene period, or Wasatchian in the NALMA classification.Quilchena, British Columbia Quilchena ( thp, q̓əłmíx) is an unincorporated community located on the south shore of Nicola Lake near the city of Merritt, British Columbia, Canada in that province's Nicola Country region. On the former main route between Merritt and Ka ...

where the species is associated with the leaf

morphospecies In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

Eucommia rolandii ''Eucommia rolandii'' is an extinct species of flowering plant in the family Eucommiaceae. ''E. rolandii'' is known from four fossil leaves found in Middle Eocene deposits of British Columbia, Canada and Mississippi, United States. ''E. rolan ...

'' are the northern most. Fossils recovered from the Ypresian

Green River Formation The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes in three basins along the present-day Green River in Colorado, Wyoming, and Utah. The sediments are deposited in very fine ...

outcrops near Rainbow, Utah, Wardell Ranch and

Douglas Pass Douglas Pass, elevation , is a mountain pass in the Book Cliffs of western Colorado. It is located in Garfield County and is traversed by State Highway 139. The pass divides the watersheds of West Douglas Creek to the north and East Salt Creek ...

extended the geographic range to the south. Fossils from both the middle Eocene

Clarno Formation Clarno may refer to: Locations * Clarno, Oregon * Clarno, Wisconsin ** Clarno (community), Wisconsin *Clarno Township, Lake County, South Dakota Lake County is a county in the U.S. state of South Dakota. As of the 2020 United States Census, t ...

and the late Eocene

John Day Formation The John Day Formation is a series of rock strata exposed in the Picture Gorge district of the John Day River basin and elsewhere in north-central Oregon in the United States. The Picture Gorge exposure lies east of the Blue Mountain uplift, whi ...

extended the southwestern range of the species into Central Oregon. Among the youngest occurrences of the species are fossils from the Late Eocene

Florissant Formation The Florissant Formation is a sedimentary geologic formation outcropping around Florissant, Teller County, Colorado. The formation is noted for the abundant and exceptionally preserved insect and plant fossils that are found in the mudstones and ...

of Colorado. All the fossils studied from Washington, British Columbia, Oregon, Colorado, and Utah fall into the range of variation seen in specimens from the Renova Formation. The Clarno formation specimens show a slightly lower average length to width ratio, but were still assigned to ''E. montana''.

Description

The asymmetrical fruits of ''Eucommia montana'' are composed of two flattened nutlets with narrow surrounding wings. The fruit tips are generally rounded with a stigmatic cleft located off center of the apex as a result of the fruit asymmetry. The fruits range from in length with an average length of . They vary in width from . Fruits of ''E. montana'' are composed of a single mature carpel, with the second carpel present as a narrow strip of tissue that is usually just over half the length of the mature carpel. The presence of preserved,

polymerized In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many for ...

latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well. In nature, latex is found as a milky fluid found in 10% of all flowering plants (angiosperms ...

threads on the fossils from Quilchena and the Klondike Mountain Formation confirm the fossils are ''Eucommia'' seeds.

References

External links

{{Taxonbar, from=Q5406192 †Eucommia montana Trees of the United States Trees of Canada Fossil taxa described in 1940 Plants described in 1940 Ypresian plants of North America Extinct flora of North America Klondike Mountain Formation Coldwater Beds Clarno Formation