Menoceras
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Menoceras ("Crescent Horns"<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>) is a genus of extinct, small rhinocerotids endemic to most of southern North America and ranged as far south as Panama during the early Miocene epoch. It lived from around 23.1-12.5 Ma, existing for approximately Template:Mya.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Description
Menoceras was much smaller than any living rhinoceros, with the genus being compared in size to a sheep<ref name=":0">Template:Cite journal</ref> or a pig,<ref name=":52">D.R. Prothero "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</ref> an with estimated bodymass of Template:Convert.<ref name=":4">Template:Cite journal</ref> 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.<ref name=":0" /> Menoceras along with Diceratherium is unique in having paired horns among rhinocerotids.<ref name=":52" /> Both sexes of Menoceros grew to a length of Template:Convert long.Template:Cn
Paleobiology
Menoceras roamed across a tropical, savanna-like grassland and plains environment that covered much of North America.<ref>Prothero, 2005</ref> Because of the massive accumulations of fossil 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, and Cady Mountains Horse Quarry, San Bernardino County, California.<ref>PaleoDB collection 19233, authorized by Dr. John Alroy, May 15, 2002.</ref>
Taxonomy
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Menoceras was named by Troxell and assigned to Rhinocerotidae 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.<ref>D. R. Prothero, C. Guerin, and E. Manning. 1989. The history of the Rhinocerotoidea. In D. R. Prothero and R. M. Schoch (eds.), The Evolution of Perissodactyls 321-340.</ref> Tanner (1969), Wilson and Schiebout (1981), Prothero and Manning (1987), Carroll (1988) and Prothero et al. (1989); and to Menoceratinae by Prothero (1998).<ref>D. R. Prothero. 1998. Rhinocerotidae. In C. M. Janis, K. M. Scott, and L. L. Jacobs (eds.), Evolution of Tertiary mammals of North America 595-605.</ref> Although some researchers have considered Menoceras to be an early member/relative of Elasmotheriinae,<ref>Template:Cite journal</ref> other studies have placed Menoceras as less closely related to Elasmotheriinae than Elasmotheriinae is to modern rhinoceroses (Rhinocerotinae)<ref name=":1">Template:Cite journal</ref>
Cladogram of Rhinocerotidae after Borrani et al. 2025<ref name=":1" />Template:Clade
Fossil distribution
Fossil distribution is as far north as New Jersey, south to Florida (3 collections) and Texas (6 collections), as far west as Nebraska (7 collections) and California (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)"<ref>Cucaracha Formation, Gaillard Cut, Panama. J. Alroy. 2002. Synonymies and reidentifications of North American fossil mammals.</ref> It was reposited in the Smithsonian Institution, Washington, D.C. Other sites:
- Lay Ranch Beds, Goshen County, Wyoming, 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, 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. Template:ISBN