''Nesodon'' ("

island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island ...

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, t ...

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 ...

(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 belonging to the extinct order

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

which inhabited southern

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

during the

Late Oligocene The Chattian is, in the geologic timescale, the younger of two ages or upper of two stages of the Oligocene Epoch/ Series. It spans the time between . The Chattian is preceded by the Rupelian and is followed by the Aquitanian (the lowest stage ...

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: Origin: The name Owen is of Irish and Welsh origin. Its meanings range from noble, youthful, and well-born. Gender: Owen is historically the masculine form of the name. Popular feminine variations include Eowyn and Owena. ...

(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 southwestern North America ...

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

, which included the well-known

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological 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 finally confirmed in ...

genus ''

Toxodon ''Toxodon'' (meaning "bow tooth" in reference to the curvature of the teeth) is an extinct genus of South American mammals from the Late Miocene to early Holocene epochs (Mayoan to Lujanian in the SALMA classification) (about 11.6 million to 1 ...

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

endemic Endemism is the state of a species being found 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 found else ...

. In particular, fossils of ''Nesodon'' are known from late early Miocene ( Santacrucian SALMA) deposits of

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

and

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...

.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 of ''Nesodon'' shows features typical of living

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and other ...

(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.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.org * Deseado and

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

* Chucal and

Río Frías Formation Río Frías Formation ( es, Formación Río Frías) is a Middle Miocene geologic formation made up sedimentary rock located in Aysén Region, western Patagonia. The formation crops out along the upper couse of Cisnes River ( es, Río Cisnes).Mar ...

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 {{paleo-mammal-stub