''Nesodon'' ("

island An island or isle is a piece of land, distinct from a continent, completely surrounded by water. There are continental islands, which were formed by being split from a continent by plate tectonics, and oceanic islands, which have never been ...

tooth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tea ...

Palmer Palmer may refer to: People and fictional characters * Palmer (pilgrim), a medieval European pilgrim to the Holy Land * Palmer (given name), including a list of people and fictional characters * Palmer (surname), including a list of people and f ...

(1904) p. 457. is a genus of

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

belonging to the

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Notoungulata Notoungulata is an extinct order of ungulates that inhabited South America from the early Paleocene to the end of the Pleistocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms re ...

which inhabited southern

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

during the

Late Oligocene The Chattian is, in the geologic timescale The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the pro ...

living from 29.0 to 16.3 Ma and existed for approximately . It had a relatively large size, weighing up to 554 kg (1221 lbs) and reaching 1.5 m in height.D.Patterson, Bruce (2012) ''Bones, Clones, and Biomes: The History and Geography of Recent Neotropical Mammals'' p.92

Taxonomy

''Nesodon'' was named by

Owen Owen may refer to: People and fictional characters * Owen (name), including a list of people and fictional characters with the given name or surname Places United States * Owen, Missouri, a ghost town * Owen, Wisconsin * Owen County, Indiana ...

(1846). It was assigned to

Toxodontidae Toxodontidae is an extinct family of notoungulate mammals, known from the Oligocene to the Holocene (11,000 BP) of South America, with one genus, '' Mixotoxodon'', also known from the Pleistocene of Central America and southern North America (a ...

by Carroll (1988). It was an early member of the family

, which included the well-known

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

genus ''

Toxodon ''Toxodon'' (meaning "bow tooth" in reference to the curvature of the teeth) is an extinct genus of large ungulate native to South America from the Pliocene to the end of the Late Pleistocene. ''Toxodon'' is a member of Notoungulata, an order of ...

''. Like almost all toxodontids, ''Nesodon'' was

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

. In particular, fossils of ''Nesodon'' are known from late early Miocene (

Santacrucian The Santacrucian age is a period of geologic time (17.5 – 16.3 Mya (unit), Ma) within the Early Miocene epoch of the Neogene, used more specifically with South American land mammal age, SALMA classification in South America. It follows the Colhue ...

SALMA) deposits of

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

and

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

.Croft et al. (2004), p. 5. Three species of ''Nesodon'' are recognized including a larger species, ''N. imbricatus'', and a smaller species, ''N. conspurcatus''.Croft et al. (2004), pp. 7–8. A poorly known and possibly invalid third species, ''N. cornutus'', was similar to ''N. imbricatus'' but may have had a small horn on its head. All species of ''Nesodon'' were larger than species of the contemporary toxodontid '' Adinotherium''. The

dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiology ...

of ''Nesodon'' shows features typical of living

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to free range (roam around) and consume wild vegetations in order to feed conversion ratio, convert the otherwise indigestible (by human diges ...

(grass-eating) mammals, but a study of wear on the enamel of ''N. imbricatus'' suggests that it was a browser (leaf eater) that may have supplemented its diet with fruit or

bark Bark may refer to: Common meanings * Bark (botany), an outer layer of a woody plant such as a tree or stick * Bark (sound), a vocalization of some animals (which is commonly the dog) Arts and entertainment * ''Bark'' (Jefferson Airplane album), ...

.Townsend & Croft (2008) p. 225.

Classification

In 2014, a study identifying a new species of ''Nesodon'', ''N. taweretus'', resolved the families phylogenetic relations, deriving the cladogram shown below:

Distribution

Fossils of ''Nesodon'' have been found in:''Nesodon''
at

Fossilworks Fossilworks was a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database, a large relational database assembled by hundreds of paleontologists from around the world. History Fossilworks was cr ...

.org * Deseado and

Santa Cruz Formation The Santa Cruz Formation is a geological formation in the Magallanes Basin, Magallanes/Austral Basin in southern Patagonia in Argentina and adjacent areas of Chile. It dates to the late Early Miocene epoch, and is contemporaneous with the eponym ...

* Chucal and

Río Frías Formation Río Frías Formation () is a Miocene, Middle Miocene geologic formation made up sedimentary rock located in Aysén Region, western Patagonia. The formation crops out along the upper course of Cisnes River ().Marshall & Salinas, 1990 Marsupial fos ...

References

Bibliography

* * McKenna, Malcolm C., and Bell, Susan K. 1997. ''Classification of Mammals Above the Species Level.'' Columbia University Press, New York, 631 pp. * * Toxodonts Prehistoric placental genera Miocene mammals of South America Friasian Santacrucian Colhuehuapian Deseadan Neogene Argentina Fossils of Argentina Neogene Chile Fossils of Chile Fossil taxa described in 1846 Taxa named by Richard Owen Austral or Magallanes Basin Santa Cruz Formation {{notoungulate-stub