''Eucommia eocenica'' 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. 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 preserved ...

fruits found in the middle

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' ...

Claiborne Formation The Claiborne Formation or Claiborne Group is a geologic formation in Arkansas, Illinois, Kentucky, and Texas. It preserves fossils dating back to the Paleogene period . See also * List of fossiliferous stratigraphic units in Kentucky Thi ...

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 state in the Southeastern region of the United States. Tennessee is the 36th-largest by area and the 15th-most populous of the 50 states. It is bordered by Kentucky to th ...

Missouri Missouri 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 is bordered by eight states (tied for the most with Tennessee ...

, and

Mississippi Mississippi () is a state in the Southeastern region of the United States, bordered to the north by Tennessee; to the east by Alabama; to the south by the Gulf of Mexico; to the southwest by Louisiana; and to the northwest by Arkansas. Miss ...

. Two fossils of the species were first described by

Edward W. Berry Edward Wilber Berry (February 10, 1875 – September 20, 1945) was an American paleontologist and botanist; the principal focus of his research was paleobotany. Early life Berry was born February 10, 1875, in Newark, New Jersey, and finished hig ...

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 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 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 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 ...

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 the United States Fossil taxa described in 1940 Fossil taxa described in 1930 Plants described in 1940 Eocene plants Extinct flora of North America