''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 o ...

endemic to most of southern

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

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 Cos ...

during the early

Miocene The Miocene ( ) is the first 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 means "less recen ...

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 extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

Diceratherium ''Diceratherium'' (meaning "two horned beast") is an extinct genus of rhinoceros endemic to North America, Europe, and Asia during the Oligocene through Miocene living from 33.9 to 11.6 mya, existing for approximately . Mass estimates for the ...

'', 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 natur ...

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

. 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.

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 language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

(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 southwe ...

(7 collections) and

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

(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,

Goshen County, Wyoming Goshen County is a county in the U.S. state of Wyoming. As of the 2020 United States Census, the population was 12,498. Its county seat is Torrington. The eastern boundary of the County borders the Nebraska state line. Goshen County produces m ...

, a deposit of several carnivores and herbivores. *Agate Springs Quarries, Sioux County, Nebraska, a deposit of Miocene herbivores and carnivores such as '' Moropus elatus'', '' Cynelos'', ''

Cephalogale ''Cephalogale'' is an extinct genus of hemicyonine bear which lived in the Oligocene and Early Miocene epochs in North America and Europe. It lived from around 28.4—20.0 Mya. Before it was reconsidered to be close to the ancestry of hemicyo ...

'', and a number of Artiodactyla. *Martin Canyon Quarry A, Logan County, Colorado, 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