''Moropus'' (meaning "slow foot") is an extinct genus of large

perissodactyl Odd-toed ungulates, mammals which constitute the taxonomic order Perissodactyla (, ), are animals—ungulates—who have reduced the weight-bearing toes to three (rhinoceroses and tapirs, with tapirs still using four toes on the front legs) o ...

("odd-toed" ungulate)

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

in the

chalicothere Chalicotheres (from Greek '' chalix'', "gravel" and '' therion'', "beast") are an extinct clade of herbivorous, odd-toed ungulate (perissodactyl) mammals that lived in North America, Eurasia, and Africa from the Middle Eocene until the Early Plei ...

family. They were endemic to

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 ...

during the

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 ...

from ~20.4—13.6 Mya, existing for approximately . ''Moropus'' belonged to the schizotheriine subfamily of chalicotheres, and has the best fossil record of any member of this group; numbers of individuals, including complete skeletons, have been found. The closest extant relatives of ''Moropus'' are other perissodactyls:

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 ...

rhino 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 ...

s, and

tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a pig, with a short, prehensile nose trunk. Tapirs inhabit jungle and forest regions of South and Central America, with one species inhabit ...

Description

Like other

s, ''Moropus'' differed from typical ungulates in having large claws, rather than hooves, on the feet. Three large, highly compressed claws on each front foot were supported inside by fissured bony phalanges, a structure similar to the large claws of ground sloths. The name ''Moropus'' translates to "slow (or sloth) foot", implying it was a clumsy mover. However, as with all schizotheriines, the articulation of the phalangeal (finger) bones shows that ''Moropus'' could retract the claws enough to walk smoothly with the front feet in a normal digitigrade stance, lifting the claws by hyperextension of the phalangeal hook. ''Moropus'' was one of the largest chalicotheres, standing about tall at the shoulder. Like other schizotheriines, the teeth were adapted to browsing, and the narrow skull with high nasal bones comes to a spoon-shaped tip, a characteristic common to leaf-eating mammals that browse selectively, grasping their food with mobile lips and a long tongue. The pelvis and hindlimbs would have allowed living individuals to rear up on their hind legs, using the front claws to hook tree branches and pull them within reach of the lips and tongue. Measurements of multiple individuals in at least one species (''M. elatus'') suggest there was

sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

, with one sex larger than the other. ''Moropus'' was an uncommon animal in the woodland and savanna environments where it lived. However, at the Agate Springs bonebed in Nebraska, the remains of seventeen individuals were found in a thirty-six foot area, which suggests that in at least some situations ''Moropus'' came together in groups. The front and back legs of this genus were more similar in length than most advanced chalicotheres, which may indicate it was better adapted to life in more open environments, spending less time standing at trees and more time walking and running. Moropus Head

Fossil distribution

*Phillips Ranch,

Kern County, California Kern County is a county (United States), county located in the U.S. state of California. As of the 2020 United States Census, 2020 census, the population was 909,235. Its county seat is Bakersfield, California, Bakersfield. Kern County comprise ...

estimated age: ~18.7 Mya. *Stewart Spring (UCMP 2027), Mineral County and

Esmeralda County, Nevada Esmeralda County is a County (United States), county in the southwestern portion of the U.S. state of Nevada. As of the 2020 United States census, 2020 census, the population was 729, making it the least populous county in Nevada. Esmeralda Coun ...

estimated age: ~18.7 Mya. *Stage Hill I, aka Millennium's End Quarry,

Scotts Bluff County, Nebraska Scotts Bluff County is a county on the western border of the U.S. state of Nebraska. As of the 2020 United States Census, the population was 36,084. Its county seat is Gering, and its largest city is Scottsbluff. Scotts Bluff County is include ...

estimated age: ~21.6—21.5 Mya. *Sucker Creek site,

Sucker Creak Formation Sucker may refer to: General use * Lollipop or sucker, a type of confection * Sucker (slang), a slang term for a very gullible person * Hard candy ** Cough drop ** Mint (candy) Biology * Sucker (botany), a term for a shoot that arises undergro ...

Malheur County, Oregon Malheur County () is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 31,571. Its county seat is Vale, and its largest city is Ontario. The county was named after the Malheur River, which runs thr ...

~16.4 Mya. *Anderson Ranch Formation, Agate Fossil Beds National Monument,

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 ...

estimated age ~ 21.3-19.2 Mya.

Species distributions

* ''M. elatus'' -

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

* ''M. hollandi'' -

Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...

, Nebraska * ''M. merriami'' -

Nevada Nevada ( ; ) is a U.S. state, state in the Western United States, Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. N ...

, Nebraska * ''M. oregonensis'' -

Oregon Oregon () is a U.S. state, state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington (state), Washington, while the Snake River delineates much of it ...

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 ...

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 ...

References

Cambridge Journals Online, Journal of Zoology
{{Taxonbar, from=Q133086 Chalicotheres Miocene odd-toed ungulates Miocene mammals of North America White River Fauna Miocene genus first appearances Fossil taxa described in 1877 Taxa named by Othniel Charles Marsh

Description

Fossil distribution

Species distributions

See also

References