Mesoreodon is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of terrestrial

Terrestrial animal

Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...

 herbivore

Herbivore

Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

 of the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Merycoidodontidae, subfamily Merycoidodontinae (the oreodont

Oreodont

Oreodons, sometimes called prehistoric "ruminating hogs," were a family of cud-chewing plant-eater with a short face and tusk-like canine teeth...

s), endemic to North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 during the Whitneyan

Whitneyan

The Whitneyan North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 33,300,000 to 30,800,000 years BP, a period of . It is usually considered to fall within the Early Oligocene...

 stage of the Oligocene

Oligocene

The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...

-Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 epochs (33—20.6 mya) existing for approximately .

Taxonomy

Mesoreodon was named by Scott (1893) and its type is Mesoreodon chelonyx. It was synonymized subjectively with Eporeodon by Lander (1998). It was assigned to Merycoidodontidae by Stevens and Stevens (1996).

Morphology

It was a large animal and ate the numerous low-growing plants and early grasses that sprung up on the plains of North America. It had a rather robust jaw, and like all oreodonts, sharp canine teeth.

Unlike many other oreodonts, who were restricted to certain habitats and places, Mesoreodon seemed to have been a cosmopolite. Fossils of Mesoreodon have been found in the Miocene deserts of California, the prairies of Nebraska, Wyoming, and South Dakota, southeastern Idaho, John Day Fossil Beds in Oregon, and Florida. In fact, Mesoreodon is the only Florida oreodont known from a complete skeleton, odd, since oreodonts had a continent-wide dominance until their extinction. They lived in all environments, and must have been very adaptable.

Mesoreodon had ossified vocal cords; the only other animal to have these in modern times is the howler monkey

Howler monkey

Howler monkeys are among the largest of the New World monkeys. Fifteen species are currently recognised. Previously classified in the family Cebidae, they are now placed in the family Atelidae. These monkeys are native to South and Central American forests...

. Mesoreodon may have been a "screaming oreodont" using loud noises to intimidate its enemies and rivals.

Four specimens were examined by M. Mendoza for body mass and estimated to have a weight of:

• Specimen 1: 228.6 kg (504 lbs).
• Specimen 2: 162.2 kg (357.5 lbs).
• Specimen 3: 144.8 kg (319.2 lbs).
• Specimen 4: 202.4 kg (446.2 lbs).

Fossil distribution

Fossils were uncovered from Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 to California

California

California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...

, Oregon

Oregon

Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...

, Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

, and Nebraska

Nebraska

Nebraska is a state on the Great Plains of the Midwestern United States. The state's capital is Lincoln and its largest city is Omaha, on the Missouri River....

.

Additional References

• San Diego Museum of Natural History

• Idaho Museum of Natural History, Collections