''Acer taurocursum'' is an extinct

maple ''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since http ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

in the family

Sapindaceae The Sapindaceae are a family of flowering plants in the order Sapindales known as the soapberry family. It contains 138 genera and 1858 accepted species. Examples include horse chestnut, maples, ackee and lychee. The Sapindaceae occur in tempera ...

described from a single

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 ...

samara Samara ( rus, Сама́ра, p=sɐˈmarə), known from 1935 to 1991 as Kuybyshev (; ), is the largest city and administrative centre of Samara Oblast. The city is located at the confluence of the Volga and the Samara (Volga), Samara rivers, with ...

found in

Late Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "daw ...

lakebed sediments exposed in the state of

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

, US. It is one of several extinct species placed in the living section '' Rubra''.

History and classification

''Acer taurocursum'' is represented by a solitary fossil specimen from the northeasternmost part of Nevada. The specimen was described by

Jack A. Wolfe Jack Albert Wolfe (1936–2005) was a United States Geological Survey paleobotanist and paleoclimatologist best known for his studies of Tertiary climate in western North America through analysis of fossil A fossil (from Classical Latin ...

and

Toshimasa Tanai Toshimasa is a masculine Japanese given name. Possible writings Toshimasa can be written using many different combinations of kanji characters. Some examples: *敏正, "agile, righteous" *敏雅, "agile, elegant" *敏昌, "agile, clear" *敏政, ...

from the "Bull Run" flora UCMP location P562, which was preserved in lacustrine sedimentation associated with extensive intermittent volcanism between .

Radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares t ...

of the layers of volcanic ash above and below the flora reported in 1966 indicated an age of approximately . The Bull Run flora, Copper Basin flora, and Elko flora were formed in the same time frame as a result of the activity. These three floras were possibly tied to the Salmon and Cow Creek floras of Central Idaho, and possibly with the John Day Formations Sheep rock flora in Oregon. ''Acer taurocursum'' is one of six ''Acer'' species to be described by Wolfe and Tanai in 1987 from the "Bull Run" flora, with the others being '' A. elkoanum'', '' A. eonegundo'', '' A. cadaver'', '' A. eomediunum'', and '' A. axelrodi''. Like ''A. taurocursum'', ''A. cadaver'' is described from fruits. ''Acer axelrodi'', ''A. elkoanum'', and ''Acer eomediunum'' are known from both leaves and fruits, while ''A. eonegundo'' is only described form foliage. Wolfe and Tanai noted that ''A. taurocursum'' is the oldest record of the ''Acer'' section ''Eriocarpa''. That section is now considered part of ''Acer'' section ''Rubra''.Flora of the Carolinas, Virginia, and Georgia
/ref> The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

for ''Acer taurocursum'' is a part specimen numbered UCMP 9089, which at the time of description was preserved in the University of California Museum of Paleontology in

Berkeley, California Berkeley ( ) is a city on the eastern shore of San Francisco Bay in northern Alameda County, California, United States. It is named after the 18th-century Irish bishop and philosopher George Berkeley. It borders the cities of Oakland and Emer ...

. The specimen was studied by paleobotanists

of the United States Geological Survey, Denver office and Toshimasa Tanai of Hokkaido University. Wolfe and Tanai published their 1987

type description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

for ''A. taurocursum'' in the ''Journal of the Faculty of Science, Hokkaido University''. The

etymology Etymology ()The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the Phonological chan ...

of the chosen

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

''taurocursum'' is in recognition of the type location for the species in the Bull Run flora of Nevada.

Description

The general shape of the ''A. taurocursum'' nutlet is narrow and elliptic, moderately inflated, and it has a rounded tip end. The nutlet is wide and in length. The overall length of the samara is approximately and a wing width of , which is placed almost entirely behind the nutlet. The paired samaras of the species have a 20° attachment angle. The wing venation is formed by approximately twenty veins that merge along the upper margin of the wing before acutely dichotomizing and anastomosing in the wing membrane. The shape of the nutlet suggested to Wolfe and Tanai placement into ''Acer'' section ''Eriocarpa''.

References

{{Taxonbar, from=Q9579419 taurocursum Prehistoric angiosperms Plants described in 1987 Fossil taxa described in 1987 Eocene plants Flora of Nevada Extinct flora of North America