''Menoceras'' ("Crescent Horns") is a genus of extinct, small

rhinoceros A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant species (or numerous extinct species) of odd-toed ungulates in the family Rhinocerotidae. (It can also refer to a member of any of the extinct species ...

endemic to most of southern North America and ranged as far south as

Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Co ...

during the early

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

epoch. It lived from around 30.7—19.7 Ma, existing for approximately .

Description

Male ''Menoceras'' sported two horns side by side at the tip of the nose, whereas the females were hornless. All other rhino genera, save the related

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

'' Diceratherium'', have their horns arranged one behind the other. Either gender of ''Menoceros'' grew to a length of long.

Paleobiology

''Menoceras'' roamed across a tropical,

savanna A savanna or savannah is a mixed woodland- grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

-like

grassland A grassland is an area where the vegetation is dominated by grasses ( Poaceae). However, sedge ( Cyperaceae) and rush ( Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur na ...

and

plain In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or uplands ...

s environment that covered much of North America. Because of the massive accumulations of

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 ...

bones of this animal, particularly at Agate Springs Nebraska, ''Menoceras'' may have lived in large herds. Other sites include Martin-Anthony site

Martin County, Florida Martin County ( es, Condado de Martín, link=) is a county located in the Treasure Coast region of the state of Florida, in the United States. As of the 2020 census, the population was 158,431. Its county seat is Stuart. Martin County is in t ...

, and Cady Mountains Horse Quarry,

San Bernardino County, California San Bernardino County (), officially the County of San Bernardino, is a county located in the southern portion of the U.S. state of California, and is located within the Inland Empire area. As of the 2020 U.S. Census, the population was 2,181, ...

Taxonomy

''Menoceras'' was named by Troxell and assigned to

Rhinocerotidae A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant species (or numerous extinct species) of odd-toed ungulates in the family Rhinocerotidae. (It can also refer to a member of any of the extinct species ...

by Troxell in 1921. It was synonymized subjectively with ''Diceratherium'' by Matthew in 1931 and Wood in 1964. Again assigned to Rhinocerotidae by Prothero, Guerrin, Manning in 1989. Tanner (1969), Wilson and Schiebout (1981), Prothero and Manning (1987), Carroll (1988) and Prothero et al. (1989); and to Menoceratinae by Prothero (1998).

Fossil distribution

Fossil distribution is as far north as

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delaware ...

, south to

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

(3 collections) and

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

(6 collections), as far west as

Nebraska Nebraska () is a state in the Midwestern region of the United States. It is bordered by South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Kansas to the south; Colorado to the sout ...

(7 collections) and

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

(2 collections). The Panamanian find was determined to be 19.7 Ma (AEO). It was found in the Gaillard Cut in Panama in "a 45 m thick section (narrow stratigraphic interval)"Cucaracha Formation, Gaillard Cut, Panama. J. Alroy. 2002. Synonymies and reidentifications of North American fossil mammals. It was reposited in the

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Founded ...

, Washington, D.C. Other sites: *Lay Ranch Beds,

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, a deposit of several carnivores and herbivores. *Agate Springs Quarries,

Sioux County, Nebraska Sioux County is a county in the U.S. state of Nebraska. As of the 2010 United States Census, the population was 1,311. Its county seat is Harrison. Sioux County is included in the Scottsbluff, NE Micropolitan Statistical Area. In the Nebrask ...

, a deposit of Miocene herbivores and carnivores such as '' Moropus elatus'', ''

Cynelos '' Cynelos'' is a large extinct genus of bear dogs which inhabited North America, Europe, and Africa from the Early Miocene subepoch to the Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene Epoch made up ...

'', '' Cephalogale'', and a number of

Artiodactyla The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...

. *Martin Canyon Quarry A,

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, a very substantial number of carnivores and herbivores.

Notes

References

*Prothero, Donald R. 2005. ''The Evolution of North American Rhinoceroses.'' Cambridge University Press, Cambridge, 218 pp. {{Taxonbar, from=Q135708 Miocene rhinoceroses Miocene mammals of North America Fossil taxa described in 1921