Merycoidodon
Encyclopedia
Merycoidodon is an extinct genus
of terrestrial
herbivore
of the family
Merycoidodontidae, subfamily Merycoidodontinae (oreodont
),
more popularly known by the name Oreodon ("Hillock teeth") endemic to North America
during the Late Eocene-Early Miocene
subepochs (38—16.3 mya) existing for approximately .
by Cope (1884); it was considered a nomen dubium
by Sinclair (1924); it was considered a nomen vanum by Lander (1998). It was assigned to Merycoidodontidae by Joseph Leidy
(1848), Thorpe (1937), Scott (1940), Galbreath (1953), Toohey (1959) and Stevens and Stevens (1996).
Most researchers in paleobiology
and paleontology
, however, now use the antecedent genus Merycoidodon to refer to this Oligocene
epoch oreodont
. The name "Oreodon" is actually a synonym of the fish genus Orodus
, and is, thus, not a valid scientific name.
Taxonomically
speaking, Merycoidodon (a.k.a. Oreodon) belongs to the family "Merycoidodontidae" (once known as "Oreodontidae"), a group of artiodactyls related to camel
s that were endemic to North America. Its ancestors date back to the Eocene
and its last descendants are known from the Pliocene
, so that oreodonts, broadly speaking, lived throughout the whole of the
Tertiary
era.
Merycoidodon would have somewhat resembled a pig
in appearance, but had a longer body, at about 1.4 metres (4.6 ft), and short limbs.
The fore limbs had five toes (although the first one was vestigial), while the hind limbs had four. Given the shape of the limbs, it is unlikely that the animals would have been able to run fast. Unlike modern ruminant
s, they had a full set of teeth, although the molars were adapted for grinding up tough vegetation. Notably, they had strong, and very striking, canines.
The skulls of Mercyoidodon have a pit in front of the eyes. Similar pits are found in the skulls of modern deer
, where they contain a scent gland
used for marking territory. Although Merycoidodon was not directly related to deer, it seems likely that it possessed a similar gland, which may imply that it, too, was territorial.
Oreodonts lived in large herds and moved about from place to place. They seem to have had a predilection for well-watered regions, where food was plentiful and succulent. The number of fossils found implies that, at one time, oreodonts were as plentiful in south Dakota
as zebra
s are today in the steppe
s of North Africa
.
Four specimens were examined by M. Mendoza for body mass and estimated to have a weight of:
and Texas
, and Oregon
.
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 (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...
),
more popularly known by the name Oreodon ("Hillock teeth") 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 Late Eocene-Early Miocene
Early Miocene
The Early Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Aquitanian and Burdigalian stages....
subepochs (38—16.3 mya) existing for approximately .
Taxonomy
Merycoidodon was named by Leidy (1848). Its type is Merycoidodon culbertsoni. It was considered a nomen nudumNomen nudum
The phrase nomen nudum is a Latin term, meaning "naked name", used in taxonomy...
by Cope (1884); it was considered a nomen dubium
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
by Sinclair (1924); it was considered a nomen vanum by Lander (1998). It was assigned to Merycoidodontidae by Joseph Leidy
Joseph Leidy
Joseph Leidy was an American paleontologist.Leidy was professor of anatomy at the University of Pennsylvania, and later was a professor of natural history at Swarthmore College. His book Extinct Fauna of Dakota and Nebraska contained many species not previously described and many previously...
(1848), Thorpe (1937), Scott (1940), Galbreath (1953), Toohey (1959) and Stevens and Stevens (1996).
Most researchers in paleobiology
Paleobiology
Paleobiology is a growing and comparatively new discipline which combines the methods and findings of the natural science biology with the methods and findings of the earth science paleontology...
and paleontology
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
, however, now use the antecedent genus Merycoidodon to refer to this 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...
epoch 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...
. The name "Oreodon" is actually a synonym of the fish genus Orodus
Orodus
Orodus is an extinct genus of cartilaginous fish that lived from the late Pennsylvanian to the early Permian in what is now North America.-Sources:...
, and is, thus, not a valid scientific name.
Taxonomically
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
speaking, Merycoidodon (a.k.a. Oreodon) belongs to the family "Merycoidodontidae" (once known as "Oreodontidae"), a group of artiodactyls related to camel
Camel
A camel is an even-toed ungulate within the genus Camelus, bearing distinctive fatty deposits known as humps on its back. There are two species of camels: the dromedary or Arabian camel has a single hump, and the bactrian has two humps. Dromedaries are native to the dry desert areas of West Asia,...
s that were endemic to North America. Its ancestors date back to the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
and its last descendants are known from the Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
, so that oreodonts, broadly speaking, lived throughout the whole of the
Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...
era.
Morphology
Pig
A pig is any of the animals in the genus Sus, within the Suidae family of even-toed ungulates. Pigs include the domestic pig, its ancestor the wild boar, and several other wild relatives...
in appearance, but had a longer body, at about 1.4 metres (4.6 ft), and short limbs.
The fore limbs had five toes (although the first one was vestigial), while the hind limbs had four. Given the shape of the limbs, it is unlikely that the animals would have been able to run fast. Unlike modern ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
s, they had a full set of teeth, although the molars were adapted for grinding up tough vegetation. Notably, they had strong, and very striking, canines.
The skulls of Mercyoidodon have a pit in front of the eyes. Similar pits are found in the skulls of modern deer
Deer
Deer are the ruminant mammals forming the family Cervidae. Species in the Cervidae family include white-tailed deer, elk, moose, red deer, reindeer, fallow deer, roe deer and chital. Male deer of all species and female reindeer grow and shed new antlers each year...
, where they contain a scent gland
Scent gland
Scent glands are found in the genital area of most mammals and in various other parts of the body, such as the underarms of humans and the preorbital glands of deer and muskox. They produce a semi-viscous fluid which contains pheromones. These odor-messengers indicate information such as status,...
used for marking territory. Although Merycoidodon was not directly related to deer, it seems likely that it possessed a similar gland, which may imply that it, too, was territorial.
Oreodonts lived in large herds and moved about from place to place. They seem to have had a predilection for well-watered regions, where food was plentiful and succulent. The number of fossils found implies that, at one time, oreodonts were as plentiful in south Dakota
South Dakota
South Dakota is a state located in the Midwestern region of the United States. It is named after the Lakota and Dakota Sioux American Indian tribes. Once a part of Dakota Territory, South Dakota became a state on November 2, 1889. The state has an area of and an estimated population of just over...
as zebra
Zebra
Zebras are several species of African equids united by their distinctive black and white stripes. Their stripes come in different patterns unique to each individual. They are generally social animals that live in small harems to large herds...
s are today in the steppe
Steppe
In physical geography, steppe is an ecoregion, in the montane grasslands and shrublands and temperate grasslands, savannas, and shrublands biomes, characterized by grassland plains without trees apart from those near rivers and lakes...
s of North Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
.
Four specimens were examined by M. Mendoza for body mass and estimated to have a weight of:
- Specimen 1: 139.2 kg (306.8 lbs).
- Specimen 2: 94.6 kg (208.5 lbs).
- Specimen 3: 112.8 kg (248.6 lbs).
- Specimen 4: 131.3 kg (289.4 lbs).
Fossil distribution
Fossils have been uncovered as far north as Alberta, Canada to FloridaFlorida
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...
and Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, and 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...
.