Macraucheniidae is a family in the extinct South American ungulate

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 ...

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 ...

, that resembled various

camelid Camelids are members of the biological family Camelidae, the only currently living family in the suborder Tylopoda. The seven extant members of this group are: dromedary camels, Bactrian camels, wild Bactrian camels, llamas, alpacas, vicuñas, ...

s. The reduced

nasal bones The nasal bones are two small oblong bones, varying in size and form in different individuals; they are placed side by side at the middle and upper part of the face and by their junction, form the bridge of the upper one third of the nose. Ea ...

of their skulls was originally suggested to have housed a small

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 ...

, similar to that of the saiga antelope. However, one study suggested that they were openings for large

moose The moose (in North America) or elk (in Eurasia) (''Alces alces'') is a member of the New World deer subfamily and is the only species in the genus ''Alces''. It is the largest and heaviest extant species in the deer family. Most adult ma ...

-like

nostril A nostril (or naris , plural ''nares'' ) is either of the two orifices of the nose. They enable the entry and exit of air and other gasses through the nasal cavities. In birds and mammals, they contain branched bones or cartilages called turbi ...

s. Conversely, prehistoric

pictographs A pictogram, also called a pictogramme, pictograph, or simply picto, and in computer usage an icon, is a graphic symbol that conveys its meaning through its pictorial resemblance to a physical object. Pictographs are often used in writing and g ...

by indigenous people seems to depict animals interpreted as macraucheniids with trunks. Their

hooves The hoof (plural: hooves) is the tip of a toe of an ungulate mammal, which is covered and strengthened with a thick and horny keratin covering. Artiodactyls are even-toed ungulates, species whose feet have an even number of digits, yet the rumi ...

were similar to those of

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 today, with a simple ankle joint and three digits on each foot. Thus, they may have been capable of rapid directional change when running away from

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill t ...

s, such as large

phorusrhacid Phorusrhacids, colloquially known as terror birds, are an extinct clade of large carnivorous flightless birds that were one of the largest species of apex predators in South America during the Cenozoic era; their conventionally accepted temporal ...

terror birds, sparassodont metatherians, giant short-faced

bears Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the No ...

('' Arctotherium)'' and

saber-toothed cat Machairodontinae is an extinct subfamily of carnivoran mammals of the family Felidae (true cats). They were found in Asia, Africa, North America, South America, and Europe from the Miocene to the Pleistocene, living from about 16 million ...

s (''

Smilodon ''Smilodon'' is a genus of the extinct machairodont subfamily of the felids. It is one of the most famous prehistoric mammals and the best known saber-toothed cat. Although commonly known as the saber-toothed tiger, it was not closely rela ...

''). Macraucheniids probably lived in large herds to gain protection against these predators, as well as to facilitate finding mates for reproduction. Theosodon patagonicum

The family Macraucheniidae includes genera such as '' Theosodon'', ''

Xenorhinotherium ''Xenorhinotherium'' is an extinct genus of macraucheniine macraucheniids, closely related to '' Macrauchenia'' of Patagonia. The type species is ''X. bahiense''.Macrauchenia''. ''Macrauchenia'' is the best-known and most recent macraucheniid. It became extinct during the

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 ...

Epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided by ...

. It was one of the few litopterns to survive the ecological pressures of the Great American Interchange between North and South America, which took place after the Isthmus of Panama rose above sea level some 3 million years ago. It may instead have died out in the aftermath of the invasion of the Americas by human hunters. When ''Macrauchenia'' died out, so too did the Macraucheniidae and the entire litoptern order. Cramauchenia insolita

Sequencing of mitochondrial DNA extracted from a ''Macrauchenia patachonica'' fossil from a cave in southern Chile indicates that ''Macrauchenia'' (and by inference, Litopterna) is the sister group to Perissodactyla, with an estimated divergence date of 66 million years ago. Analysis of collagen sequences obtained from ''Macrauchenia'' 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 to 1 ...

'' gave the same conclusion, adding

notoungulate 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 ...

s to the sister group clade.

References

Bibliography

External links

Phylogeny of Macraucheniidae
{{Taxonbar, from=Q134960 Litopterns Prehistoric mammal families Quaternary mammals of South America Neogene mammals of South America Paleogene mammals of South America Ypresian first appearances Holocene extinctions