''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 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 fruits found in the middle
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''. 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,
Missouri, and
Mississippi. 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
Roland Wilbur Brown (1893–1961) was an American paleobotanist and geologist.
Biography
Brown was born in 1893. In 1928, he was appointed as a geologist with the United States Geological Survey, where he remained until he retired in 1958. He als ...
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 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 latex 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