''Eucommia eocenica'' 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. eocenica'' 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 the middle

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 ...

Claiborne Formation deposits of the southeastern United States. ''E. eocenica'' 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. jeffersonensis'', '' E. montana'', and '' E. rowlandii''.

History and classification

''Eucommia eocenica'' is known from a number of specimens recovered from Claiborne Formation fossil sites in

Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...

Missouri Missouri (''see #Etymology and pronunciation, pronunciation'') is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. Ranking List of U.S. states and territories by area, 21st in land area, it border ...

, 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 ...

. Two fossils of the species were first described by Edward W. Berry in 1930 from the Holly Hills sand of Tennessee as ''Carpolithus banisteroides'' and ''Simaroubites eocenica'' respectively. The two fossils were reexamined by Roland W. Brown in 1940, who recognized them to belong to the same species. Brown moved the species to ''Eucommia'' as ''Eucommia eocenica'' and made ''Carpolithus banisteroides'' a synonym. The species was again examined in 1997 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. In their reexamination they noted that the species ''Leguminosites copaiferanus'' which was also described by Berry in 1930 is likely also a ''E. eocenica'' fruit rather than a separate taxon.

Description

The asymmetrical fruits of ''E. eocenica'' are composed of two flattened nutlets with narrow surrounding wings. The fruit tips are generally pointed. The fruits range from in length with an average length of . They vary in width from . ''E. eocenica'' stipes are attached to the base of the fruit at an angle of 45°, with a length ranging from . Almost all known specimens of ''E. eocenica'' are composed of a single mature carpel, with the second carpel present as a narrow strip of tissue found on the underside of the mature carpel. One known specimen is of a fruit with two mature carpels. In that specimen the fruit shows bilateral symmetry, with the stipe and the suture between the carpels being placed centrally, rather than along one side as is seen in the asymmetrical specimens. The fossils show a net of small

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 form ...

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 ...

veins. The latex, which still retains its elasticity, ranges in coloration from golden brown in more oxidized specimens to a dark brown in less oxidized specimens.

References

External links

{{Taxonbar, from=Q5406188 †Eucommia eocenica Trees of Northern America Fossil taxa described in 1940 Fossil taxa described in 1930 Plants described in 1940 Eocene plants Extinct flora of North America