HOME

TheInfoList



OR:

Astrapotheria is an extinct
order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...
of
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 ...
n and
Antarctic The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and othe ...
hoofed
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 ...
s that existed from the late
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
Middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million ...
, ."The uruguaytheriine Astrapotheriidae from the rich middle Miocene Honda Group of the upper Magdalena River valley in Colombia (...) are the youngest securely dated remains of that order in South America." Astrapotheres were large and rhinoceros-like animals and have been called one of the most bizarre orders of mammals with an enigmatic evolutionary history. This taxonomy of this order is not clear, but it may belong to
Meridiungulata South American native ungulates, commonly abbreviated as SANUs, are extinct ungulate-like mammals of controversial affinities that were indigenous to South America prior to the Great American Biotic Interchange. They comprise five major groups co ...
(along with
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 ...
,
Litopterna Litopterna (from grc, λῑτή πτέρνα "smooth heel") is an extinct order of fossil hoofed mammals from the Cenozoic era. The order is one of the five great orders of South American ungulates that were endemic to the continent, until th ...
, Pyrotheria and Xenungulata). In turn, Meridungulata is believed to belong to the extant superorder
Laurasiatheria Laurasiatheria ("laurasian beasts") is a superorder of placental mammals that groups together true insectivores ( eulipotyphlans), bats ( chiropterans), carnivorans, pangolins ( pholidotes), even-toed ungulates ( artiodactyls), odd-toed ungulat ...
. Some scientists have regarded the astrapotheres (and sometimes the Meridiungulata as a whole) as members of the clade
Atlantogenata Atlantogenata is a proposed clade of mammals containing the cohorts or superorders Xenarthra and Afrotheria. These groups originated and radiated in the South American and African continents, respectively, presumably in the Cretaceous. Together ...
. However, collagen and mitochondrial DNA sequence data analysed in 2015 places at least the notoungulates and litopterns firmly within Laurasiatheria, as 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.


Description

Their lophodont molars and tusk-like canines became extremely large and ever-growing in later astrapotheres. The upper molars lack an ectocingulum and are dominated by well-developed ectoloph and protoloph. Additional lophs formed in some derived taxa. They had lower molars with two cross-lophs, including a high protocristid, and eventually became almost
selenodont Selenodont teeth are the type of molars and premolars commonly found in ruminant herbivores. They are characterized by low crowns, and crescent-shaped cusps when viewed from above (crown view). The term comes from the Ancient Greek roots (, ' ...
. As a result, their dentition is similar to notoungulates, but it seems to have
evolved independently Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last co ...
. The cheek teeth are similar to rhinocerotoids, including similar microstructure, which indicate they had the same function.
Postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated sk ...
lly, astrapotheres are relatively robust and more or less graviportal but have slender
long bone The long bones are those that are longer than they are wide. They are one of five types of bones: long, short, flat, irregular and sesamoid. Long bones, especially the femur and tibia, are subjected to most of the load during daily activities ...
s, most notably in the hindlegs, suggesting they were amphibious. In order to support their
proboscis A proboscis () is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In invertebrates, the term usually refers to tubular mouthparts used for feeding and sucking. In vertebrates, a proboscis is an elong ...
es and large heads they had relatively long and massive necks in relation to the rest of the vertebral column. Their feet are pentadactyl with short and stout podial and metapodial bones. Most characteristic for the order are the flat
astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...
, equipped with a short neck and a flat head, articulating with both the navicular and cuboid bones; and their
calcaneus In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock. ...
with its enlarged peroneal tubercle. Three families are recognized: Eoastrapostylopidae from the late Paleocene,
Trigonostylopidae ''Trigonostylops'' is an extinct genus of South American meridiungulatan ungulate, from the Late Paleocene to Late Eocene (Itaboraian to Tinguirirican in the SALMA classification) of South America (Argentina and Peru) and Antarctica (Seymour Isl ...
from the
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 ...
-
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'', ...
, and Astrapotheriidae from the Eocene-
Miocene The Miocene ( ) is the first 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 means "less recen ...
. The Brazilian,
Itaboraian The Itaboraian ( pt, Itaboraiense) age is a period within the Early Eocene geologic time (53.0–50.0 Ma) epoch of the Paleogene, used more specifically with South American land mammal ages (SALMA). It follows the Riochican and precedes the Cas ...
''
Tetragonostylops ''Tetragonostylops'' is an extinct genus of mammal, related to Astrapotheria. It lived during the Late Paleocene, and its fossils were discovered in South America. Description This genus is only known from incomplete remains, notably a wel ...
'' and the Argentinian, Riochican '' Eoastrapostylops'' are the oldest astrapotheres. The latter, with its low-crowned and lophoselenodont cheek teeth, is considered the most primitive astrapothere. Trigonostylopids are distinct from other astrapotheres in their ear anatomy but are included in the order because of otherwise similar characters. '' Antarctodon'' is one of few eutherian mammals, as well as one of the last known terrestrial vertebrates, found in Antarctica. The most famous member of the order is undoubtedly '' Astrapotherium'', a long elephant-like animal that had lost its upper incisors and developed ever-growing canine tusks. They had lost their anterior premolars, resulting in a gap between their tusks and the
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 ...
cheek teeth. The short and retracted nasal bones indicate a moderately developed proboscis. The small Eocene '' Trigonostylops'' lacked such retracted nasals and probably also a proboscis. Other astrapotheriids, such as the Casamayoran '' Scaglia'' and '' Albertogaudrya'', were between a sheep and a tapir in size and already the largest South American mammals.


Classification

There is no scientific consensus regarding the classification within Astrapotheria. For example, originally described ''Tetragonostylops'' as a trigonostylopid but Soria 1982 and
1984 Events January * January 1 – The Bornean Sultanate of Brunei gains full independence from the United Kingdom, having become a British protectorate in 1888. * January 7 – Brunei becomes the sixth member of the Association of Southeas ...
transferred the genus to Astrapotheriidae and concluded that the remaining two genera in that family, ''Trigonostylops'' and ''Shecenia'', form a basal collateral branch within Astrapotheriidae. According to , Trigonostylopidae (including Eoastrapostylopidae) is the stem group of Astrapotheriidae. * Astrapotheriidae . Retrieved March 2013. ** '' Albertogaudrya'' ** '' Antarctodon'' ** '' Astrapodon'' ** '' Astraponotus'' ** ''
Astrapothericulus ''Astrapothericulus'' is an extinct genus of mammals, belonging to the order Astrapotheria. It lived during the Lower Miocene in what is now South America. Description This animal was as large than a tapir, and may have looked like them, as ...
'' ** '' Astrapotherium'' ** ''
Comahuetherium ''Comahuetherium'' is an extinct genus of astrapotherian mammal from the Early Miocene (Colhuehuapian age). It is a basal astrapotheriid which lived in what is now Patagonia, Argentina. The holotype was found in the Cerro Bandera Formation ...
'' ** '' Granastrapotherium'' ** '' Hilarcotherium'' **'' Liarthrus'' ** '' Maddenia'' ** ''
Parastrapotherium ''Parastrapotherium'' is an extinct genus of South American land mammal that existed from the Late Oligocene (Deseadan SALMA) to the Early Miocene (Colhuehuapian SALMA). The genus includes some of the largest and smallest known astrapother ...
'' ** '' Scaglia'' ** ''
Uruguaytherium ''Uruguaytherium'' is an extinct genus of astrapotherid mammal from the Late Oligocene to Early Miocene of South America. It was named by the Argentinean paleontologist Lucas Kraglievich in 1928, from a fragmentary fossil found in the Fray ...
'' ** '' Xenastrapotherium'' * Eoastrapostylopidae ** '' Eoastrapostylops'' *
Trigonostylopidae ''Trigonostylops'' is an extinct genus of South American meridiungulatan ungulate, from the Late Paleocene to Late Eocene (Itaboraian to Tinguirirican in the SALMA classification) of South America (Argentina and Peru) and Antarctica (Seymour Isl ...
** '' Shecenia'' ** ''
Tetragonostylops ''Tetragonostylops'' is an extinct genus of mammal, related to Astrapotheria. It lived during the Late Paleocene, and its fossils were discovered in South America. Description This genus is only known from incomplete remains, notably a wel ...
'' ** '' Trigonostylops''


References


Bibliography

* * * * * * * * * * * * * * * * * * * * * * {{Taxonbar, from=Q133684 Meridiungulata Paleocene first appearances Miocene extinctions Paleogene Antarctica Cenozoic mammals of Antarctica Cenozoic animals of Antarctica Laventan Colloncuran Friasian Santacrucian Colhuehuapian Deseadan Tinguirirican Divisaderan Mustersan Casamayoran Riochican Itaboraian Fossil taxa described in 1894 Taxa named by Richard Lydekker Prehistoric animal orders Mammal orders