Notoungulata is an extinct order of
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 ...
ian
ungulate
Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, ...
s that inhabited
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 sou ...
from the early
Paleocene
The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pala ...
to the Holocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resembling animals as disparate as rabbits and rhinoceroses. Notoungulata are the largest group of
South American native ungulates, with over 150 genera in 14 families having been described, divided into two major subgroupings,
Typotheria
Typotheria is a suborder of the extinct mammalian order Notoungulata and includes five families: Archaeopithecidae, Campanorcidae, Interatheriidae, Mesotheriidae, and Oldfieldthomasiidae. CifelliCifelli, Richard L. 1993. The phylogeny of the ...
and
Toxodontia. Notoungulates first diversified during the
Eocene
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...
. Their diversity declined during the Late
Neogene
The Neogene ( ), informally Upper Tertiary or Late Tertiary, is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago ( Mya) to the beginning of the present Quaternary Period Mya. ...
, with only the large
toxodontids persisting until the end of the
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), 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 fina ...
. Collagen analysis suggests that notoungulates are closely related to
litopterns, another group of South American ungulates, and their closest living relatives being
perissodactyls (odd-toed ungulates), including
rhinoceros
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 specie ...
es,
tapirs and
equines
''Equus'' , is a genus of mammals in the family (biology), family Equidae, which includes horses, donkeys, and zebras. Within the Equidae, ''Equus'' is the only recognized Extant taxon, extant genus, comprising seven living species. Like Equida ...
. but their relationships to other South American ungulates are uncertain. Several groups of notoungulates separately evolved ever growing teeth like rodents and lagomorphs, a distinction among ungulates only shared with ''
Elasmotherium
''Elasmotherium'' is an extinct genus of large rhinoceros endemic to Eurasia during Late Miocene through the Pleistocene, existing at least as late as 39,000 years ago in the Late Pleistocene. A more recent date of 26,000 BP is considered ...
''.
Taxonomy
Notoungulata is divided into two major suborders,
Typotheria
Typotheria is a suborder of the extinct mammalian order Notoungulata and includes five families: Archaeopithecidae, Campanorcidae, Interatheriidae, Mesotheriidae, and Oldfieldthomasiidae. CifelliCifelli, Richard L. 1993. The phylogeny of the ...
and
Toxodontia, alongside some basal groups (
Notostylopidae and
Henricosborniidae) which are potentially
paraphyletic
In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...
. Due to the isolated nature of South America, many notoungulates evolved along
convergent lines into forms that resembled mammals on other continents. Examples of this are ''
Pachyrukhos'', a notoungulate that filled an ecological niche similar to those of
rabbits
Rabbits, also known as bunnies or bunny rabbits, are small mammals in the family Leporidae (which also contains the hares) of the order Lagomorpha (which also contains the pikas). ''Oryctolagus cuniculus'' includes the European rabbit sp ...
and
hares
Hares and jackrabbits are mammals belonging to the genus ''Lepus''. They are herbivores, and live solitarily or in pairs. They nest in slight depressions called forms, and their young are able to fend for themselves shortly after birth. The gen ...
, and ''
Homalodotherium'', which resembled
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 Ple ...
s. The families
Interatheriidae
Interatheriidae is an extinct family of notoungulate mammals from South America. Interatheriids are known from the Middle Eocene (Mustersan) to the Early Pliocene (Montehermosan).McKenna & Bell, 1997Linares, 2004 These animals were principally s ...
,
Hegetotheriidae,
Mesotheriidae
Mesotheriidae ("Middle Beasts") is an extinct Family (biology), family of Notoungulata, notoungulate mammals known from the Oligocene through the Pleistocene of South America. Mesotheriids were small to medium-sized herbivorous mammals adapted fo ...
and
Toxodontidae separately evolved high crowned (
hypsodont
Hypsodont is a pattern of dentition with high-crowned teeth and enamel extending past the gum line, providing extra material for wear and tear. Some examples of animals with hypsodont dentition are cows and horses; all animals that feed on gritt ...
) ever-growing teeth. During the
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), 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 fina ...
, ''
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 t ...
'' was the largest common notoungulate. Most of the group (''
Mixotoxodon
''Mixotoxodon'' ("mixture ''Toxodon''") is an extinct genus of notoungulate of the family Toxodontidae inhabiting South America, Central America and parts of southern North America during the Pleistocene epoch, from 1,800,000—12,000 years a ...
'', ''
Piauhytherium'' and ''
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 t ...
'' being exceptions) became extinct after the landbridge between North and South America formed and allowed North American ungulates to enter South America in the
Great American Interchange
The Great American Biotic Interchange (commonly abbreviated as GABI), also known as the Great American Interchange and the Great American Faunal Interchange, was an important late Cenozoic paleozoogeographic biotic interchange event in which lan ...
, and then to out-compete the native fauna.
''Mixotoxodon'' was the only member of the group to be successful in invading Central America and southern North America, reaching as far north as Texas.
This order is united with other South American ungulates in the super-order
Meridiungulata. The notoungulate and
litoptern native ungulates of South America have been shown by studies of
collagen
Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...
and
mitochondrial DNA
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...
sequences to be a
sister group
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree.
Definition
The expression is most easily illustrated by a cladogram:
Taxon A and ...
to the
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 ...
s, making them true ungulates.
The estimated divergence date is 66 million years ago.
This conflicts with the results of some morphological analyses which favoured them as
afrotheria
Afrotheria ( from Latin ''Afro-'' "of Africa" + ''theria'' "wild beast") is a clade of mammals, the living members of which belong to groups that are either currently living in Africa or of African origin: golden moles, elephant shrews (also k ...
ns. It is in line with some more recent morphological analyses which suggested they were basal
euungulates.
Panperissodactyla has been proposed as the name of an unranked clade to include perissodactyls and their extinct South American ungulate relatives.
Cifelli has argued that Notioprogonia is
paraphyletic
In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...
, as it would include the ancestors of the remaining suborders. Similarly, Cifelli indicated that Typotheria would be paraphyletic if it excluded Hegetotheria and he advocated inclusion of Archaeohyracidae and Hegetotheriidae in Typotheria.
Notoungulata were for many years taken to include the order
Arctostylopida
Arctostylopidae is an extinct family of placental mammals from the Late Palaeocene of Eastern Asia and North America. All arctostylopid specimens in North America have been referred to the genus '' Arctostylops''.
They are animals of uncertain a ...
, whose fossils are found mainly in China. Recent studies, however, have concluded that Arctostylopida are more properly classified as
gliriforms, and that the notoungulates were therefore never found outside South and Central America.
Based on an analysis of 133 morphological characters in 50 notoungulate genera, Billet in 2011 concluded that
Homalodotheriidae
Homalodotheriidae is an extinct family comprising four genera of notoungulate mammals known from the Late Eocene ( Tinguirirican) through Late Miocene (Chasicoan) of Argentina and Chile
Chile, officially the Republic of Chile, is a coun ...
,
Leontiniidae
Leontiniidae is an extinct family comprising eighteen genera of notoungulate mammals known from the Middle Eocene (Mustersan) to Late Miocene (Huayquerian The Huayquerian ( es, Huayqueriense) age is a period of geologic time (9.0–6.8 Ma) wit ...
,
Toxodontidae,
Interatheriidae
Interatheriidae is an extinct family of notoungulate mammals from South America. Interatheriids are known from the Middle Eocene (Mustersan) to the Early Pliocene (Montehermosan).McKenna & Bell, 1997Linares, 2004 These animals were principally s ...
,
Mesotheriidae
Mesotheriidae ("Middle Beasts") is an extinct Family (biology), family of Notoungulata, notoungulate mammals known from the Oligocene through the Pleistocene of South America. Mesotheriids were small to medium-sized herbivorous mammals adapted fo ...
, and
Hegetotheriidae are the only monophyletic families of notoungulates.
Phylogeny
Orders and families
*Order Notoungulata - notoungulates
**Suborder
Notioprogonia
Notioprogonia is a suborder of the extinct mammalian order Notoungulata and includes two families, Henricosborniidae and Notostylopidae.
Notioprogonia includes the most primitive notoungulates and has argued that Notioprogonia is paraphyle ...
***Family
Henricosborniidae
***Family
Notostylopidae
**Suborder
Toxodontia
***Family
Isotemnidae
Isotemnidae is an extinct family of notoungulate mammals known from the Paleocene ( Las Flores Formation, Itaboraian) to Middle Miocene ( Honda Group, Laventan
The Laventan ( es, Laventense) age is a period of geologic time (13.8 to 11.8 Ma ...
***Family
Leontiniidae
Leontiniidae is an extinct family comprising eighteen genera of notoungulate mammals known from the Middle Eocene (Mustersan) to Late Miocene (Huayquerian The Huayquerian ( es, Huayqueriense) age is a period of geologic time (9.0–6.8 Ma) wit ...
***Family
Notohippidae
Notohippidae is a paraphyletic extinct family of notoungulate mammals from South America. Notohippids are known from the Eocene and Oligocene epochs.McKenna, Malcolm C., and Bell, Susan K. 1997. ''Classification of Mammals Above the Species Lev ...
***Family
Toxodontidae
***Family
Homalodotheriidae
Homalodotheriidae is an extinct family comprising four genera of notoungulate mammals known from the Late Eocene ( Tinguirirican) through Late Miocene (Chasicoan) of Argentina and Chile
Chile, officially the Republic of Chile, is a coun ...
**Suborder
Typotheria
Typotheria is a suborder of the extinct mammalian order Notoungulata and includes five families: Archaeopithecidae, Campanorcidae, Interatheriidae, Mesotheriidae, and Oldfieldthomasiidae. CifelliCifelli, Richard L. 1993. The phylogeny of the ...
***Family
Archaeohyracidae
Archaeohyracidae is an extinct family of notoungulate mammals known from the Paleocene through the Oligocene
The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the pr ...
***Family
Archaeopithecidae
Archaeopithecidae is an extinct family comprising two genera of notoungulate mammals, '' Teratopithecus'' and '' Archaeopithecus'', both known from the Eocene of Argentina.Campanorcidae
''Campanorco'' is an extinct genus of notoungulate mammal from the Middle Eocene Lumbrera Formation, Argentina, South America and the only member of the family
Family (from la, familia) is a group of people related either by consanguinity ...
***Family
Hegetotheriidae
***Family
Interatheriidae
Interatheriidae is an extinct family of notoungulate mammals from South America. Interatheriids are known from the Middle Eocene (Mustersan) to the Early Pliocene (Montehermosan).McKenna & Bell, 1997Linares, 2004 These animals were principally s ...
***Family
Mesotheriidae
Mesotheriidae ("Middle Beasts") is an extinct Family (biology), family of Notoungulata, notoungulate mammals known from the Oligocene through the Pleistocene of South America. Mesotheriids were small to medium-sized herbivorous mammals adapted fo ...
***Family
Oldfieldthomasiidae
Oldfieldthomasiidae is an extinct family of notoungulate mammals known from the Late Paleocene to Late Eocene of South America. The family was classified by George Gaylord Simpson in 1945 and a synonym is Acoelodidae, defined by Florentino Amegh ...
References
Bibliography
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Further reading
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{{Taxonbar, from=Q131322
Paleocene mammals
Miocene mammals of South America
Oligocene mammals
Pleistocene mammals
Ungulates
Paleocene first appearances
Pleistocene extinctions
Fossil taxa described in 1903
Pliocene notoungulates
Mammal orders