''Equus conversidens'', or the Mexican horse, is a dubious

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

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 ...

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million y ...

, now extinct, that inhabited

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 ...

. 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 ...

of ''Equus conversidens'', a partial palate, was unearthed in Pleistocene deposits northeast of Mexico City,

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. In January 1963, a partial skeleton was found in the city of

Canyon, Texas Canyon is a city in, and the county seat of, Randall County, Texas, United States. The population was 14,836 at the 2020 census. It is part of the Amarillo, Texas, metropolitan statistical area. Canyon is the home of West Texas A&M University and ...

in a white clay bed during the excavation of a basement, and was referred to ''E. conversidens'' by Dalquest and Hughes (1965), who interpreted the species as medium to small-sized, and added additional records of the species from

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 ...

(including a skeleton from Slaton),

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

Oklahoma Oklahoma (; Choctaw language, Choctaw: ; chr, ᎣᎧᎳᎰᎹ, ''Okalahoma'' ) is a U.S. state, state in the South Central United States, South Central region of the United States, bordered by Texas on the south and west, Kansas on the nor ...

Kansas Kansas () is a state in the Midwestern United States. Its capital is Topeka, and its largest city is Wichita. Kansas is a landlocked state bordered by Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the ...

and

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 ...

, synonymizing '' Equus francisci'', ''Equus tau'', ''E. littoralis'', ''E. achates'', and ''E. barcenaei'' with ''E. conversidens''. However, Winans (1985) and MacFadden (1992) challenged the validity of ''E. conversidens'' due to its minimal diagnostic value, and treated ''E. francisci'' as valid. Subsequent study confirmed the ''nomen dubium'' status of ''E. conversidens'' because the holotype was undiagnostic besides its small size.Heintzman, Peter D; Zazula, Grant D; MacPhee, Ross DE; Scott, Eric; Cahill, James A; McHorse, Brianna K; Kapp, Joshua D; et al. (2017). "A new genus of horse from Pleistocene North America". eLife. 6. doi:10.7554/eLife.29944 .

References

{{DEFAULTSORT:Equus conversidens Pleistocene mammals of North America Taxa named by Richard Owen Fossil taxa described in 1869 Equus (genus)

See also

References