''Eucommia rolandii'' 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 ''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. rolandii'' is known from four

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 ...

leaves found in

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

deposits of

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 and

Mississippi Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...

, United States. ''E. rolandii'' 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. montana''.

History and classification

''Eucommia rolandii'' is known from only two fossils, a holotype and an additional specimen referred to the species. The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

, specimen UF 11034, is housed in the paleobotanical collections of the

Florida Museum of Natural History The Florida Museum of Natural History (FLMNH) is Florida's official state-sponsored and chartered natural history museum. Its main facilities are located at 3215 Hull Road on the campus of the University of Florida in Gainesville, Florida, Gaine ...

, and is from Middle Eocene rocks of the Talahatta Formation. The specimen was recovered from strata exposed in the Bovay Clay pit near

Holly Springs, Mississippi Holly Springs is a city in and the county seat of Marshall County, Mississippi, Marshall County, Mississippi, United States, near the border with Tennessee to the north. As of the 2020 United States census, 2020 census, the population was 6,96 ...

. The other fossil is marked as specimen SFU 14748, and is part of the collections at

Simon Fraser University Simon Fraser University (SFU) is a Public university, public research university in British Columbia, Canada. It maintains three campuses in Greater Vancouver, respectively located in Burnaby (main campus), Surrey, British Columbia, Surrey, and ...

. SFU 14748 is composed of three attached leaves in association with, but not attached to, fruits identified as from the species '' E. montana'' collected from the Quilchena locality in British Columbia. ''Eucommia rolandii'' was first studied by paleobotanists Victor B. Call and David L. 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. Call and Dilcher's 1997 type description of the new species was published in the botanical journal ''

American Journal of Botany The ''American Journal of Botany'' is a monthly peer-reviewed scientific journal which covers all aspects of plant biology. It has been published by the Botanical Society of America since 1914. The journal has an impact factor of 3.038, as of 20 ...

''. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''rolandii'' was chosen in honor of the American paleobotanist Roland W. Brown who was responsible for the first identification of ''Eocommia'' fossils found in North America.

Description

The leaves are elliptical in overall shape with a pointed base and a tip that gradually tapers to a point. The length of the leaves ranges up to with a width that can reach half that at . A

petiole Petiole may refer to: *Petiole (botany), the stalk of a leaf, attaching the blade to the stem *Petiole (insect anatomy) In entomology, petiole is the technical term for the narrow waist of some hymenopteran insects, especially ants, bees, and ...

up to long is attached at the base. The leaves have a single main vein with at least five alternating pairs of secondary veins placed along its length. The lower secondary veins have a brochidodromous structuring, forming large loops that do not reach the leaf margin but curve up and attach to the next secondary up. The secondaries near the tip have a similar looping structure, but with a series of smaller loops formed by cross-veins rather than the single continuous loop of the basal secondaries. Tertiary veins run from the main vein out to the margin, some forking, and all straight to slightly wavy. The finer vein structure forms a network of irregularly shaped, polygonal

areolae The human areola (''areola mammae'', or ) is the pigmented area on the breast around the nipple. More generally, an areola is a small circular area on the body with a different histology from the surrounding tissue, or other small circular ar ...

. The margins of the leaves are serrated, with the teeth having a strong curve towards the leave tip. This results in the teeth often being pressed against the leaf margin above the tooth or against the base of the next tooth along the margin. The middle area of each tooth hosts very small veins originating in the marginal vein structure. ''E. rolandii'' leaves are notable for the preserved

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 ...

that is found on them. All the studied leaves of ''E. rolandii'' have small bundles of latex filaments that are found in all the veins. The filaments are rarely found in the areolae that are formed by the veins.

References

External links

{{Taxonbar, from=Q16752826 †Eucommia rolandii Trees of Northern America Fossil taxa described in 1997 Plants described in 1997 Eocene plants Extinct flora of North America