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

rhinocerotid A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...

s endemic to most of southern

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

and ranged as far south as

Panama Panama, officially the Republic of Panama, is a country in Latin America at the southern end of Central America, bordering South America. It is bordered by Costa Rica to the west, Colombia to the southeast, the Caribbean Sea to the north, and ...

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 23.1-12.5 Ma, existing for approximately .

Description

''Menoceras'' was much smaller than any living rhinoceros, with the genus being compared in size to a sheep or a pig,D.R. Prother
"Rhinocerotidae"
C.M. Janis, K.M. Scott, L. Jacobs (Eds.), Evolution of Tertiary Mammals of North America, Cambridge University Press, Cambridge (1998), pp. 595-605 an with estimated bodymass of . Male ''Menoceras'' sported two horns side by side at the tip of the nose, whereas the females were hornless or had greatly reduced horns, and have differently shaped

nasal bones The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Eac ...

. ''Menoceras'' along with ''

Diceratherium ''Diceratherium'' (meaning "two horned beast") is an extinct genus of rhinocerotid native to North America during the Oligocene through Miocene living from 33.9 to 11.6 mya, existing for approximately . Mass estimates for the type species, ''D. ...

'' is unique in having paired horns among rhinocerotids. Both sexes 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) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...

-like

grassland A grassland is an area where the vegetation is dominance (ecology), dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes such as clover, and other Herbaceo ...

and

plain In geography, a plain, commonly known as flatland, 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 ...

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 preserve ...

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 is a County (United States), county located in the southeastern part of the U.S. state, state of Florida, in the United States. As of the 2020 United States census, 2020 census, the population was 158,431. Its county seat is Stua ...

, and Cady Mountains Horse Quarry,

San Bernardino County, California San Bernardino County ( ), officially the County of San Bernardino and sometimes abbreviated as S.B. County, is a County (United States), county located in the Southern California, southern portion of the U.S. state of California, and is locat ...

Taxonomy

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

Rhinocerotidae A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...

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 U.S. state, state located in both the Mid-Atlantic States, Mid-Atlantic and Northeastern United States, Northeastern regions of the United States. Located at the geographic hub of the urban area, heavily urbanized Northeas ...

, south to

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

(3 collections) and

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

(6 collections), as far west as

Nebraska Nebraska ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders South Dakota to the north; Iowa to the east and Missouri to the southeast, both across the Missouri River; Ka ...

(7 collections) and

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

(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, Education center, education and Research institute, research centers, created by the Federal government of the United States, U.S. government "for the increase a ...

, 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 prod ...

, 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 2020 United States census, the population was 1,135. Its county seat is Harrison. Sioux County is included in the Scottsbluff, NE Micropolitan Statistical Area. In the Nebr ...

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

Cynelos ''Cynelos'' is a large extinct genus of amphicyonids which inhabited North America, Europe, and Africa from the Early Miocene subepoch to the Late Miocene subepoch 20.4–13.7 Annum, Mya, existing for approximately . Species * ''C. caroniavorus ...

'', ''

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 hemicyoni ...

'', and a number of

Artiodactyla Artiodactyls are placental mammals belonging to the order (biology), order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof ...

. *Martin Canyon Quarry A,

Logan County, Colorado Logan County is a county located in the U.S. state of Colorado. As of the 2020 United States census, 2020 census, the population was 21,528. The county seat is Sterling, Colorado, Sterling. The county was named for General John A. Logan. Logan ...

, 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