''Eucommia montana'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

species 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 ...

in the family Eucommiaceae. ''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 preserve ...

fruits found in

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 ...

deposits of the northwestern United States southeastern

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 ...

south to

Oregon Oregon ( , ) is a U.S. state, state in the Pacific Northwest region of the United States. It is a part of the Western U.S., with the Columbia River delineating much of Oregon's northern boundary with Washington (state), Washington, while t ...

and east to

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

and

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

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

. 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 university, public land-grant university, land-grant research university in Gainesville, Florida, United States. It is a senior member of the State University System of Florida and a preem ...

in Gainesville. In the reassessment of the species, Call and Dilcher expanded both the chronostratigraphic 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), Washington state. The formation is composed of volcanic rocks in the upper unit and volcanic plus lacu ...

of Northern

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 ...

. The slightly younger

Coldwater Beds The Coldwater Beds are a Formation (geology), geologic formation of the Okanagan Highlands in British Columbia, Canada. They preserve fossils dating back to the Ypresian stage of the Eocene Period (geology), period, or Wasatchian in the North Ame ...

outcropping near Quilchena, British Columbia where the species is associated with the leaf

morphospecies A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of classification and ...

'' Eucommia rolandii'' 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 (Colorado River), Green River in Colorado, Wyoming, and Utah. The sedimen ...

outcrops near Rainbow, Utah, Wardell Ranch and Douglas Pass,

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

Clarno Formation John Day Fossil Beds National Monument is a National monument (United States), U.S. national monument in Wheeler County, Oregon, Wheeler and Grant County, Oregon, Grant counties in east-central Oregon. Located within the John Day River basin an ...

and the late Eocene John Day Formation 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 an ...

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

latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latices are found in nature, but synthetic latices are common as well. In nature, latex is found as a wikt:milky, milky fluid, which is present in 10% of all floweri ...

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 Northern America 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