llama The llama (; or ) (''Lama glama'') is a domesticated South American camelid, widely used as a List of meat animals, meat and pack animal by Inca empire, Andean cultures since the pre-Columbian era. Llamas are social animals and live with ...

ungulate Ungulates ( ) are members of the diverse clade Euungulata ("true ungulates"), which primarily consists of large mammals with Hoof, hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined ...

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58 or

Middle Pleistocene The Chibanian, more widely known as the Middle Pleistocene (its previous informal name), is an Age (geology), age in the international geologic timescale or a Stage (stratigraphy), stage in chronostratigraphy, being a division of the Pleistocen ...

to the end of the

Late Pleistocene The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division ...

. It is a member of the extinct order Litopterna, a group of South American native ungulates distinct from the two orders which contain all living ungulates which had been present in South America since the early

Cenozoic The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...

, over 60 million years ago, prior to the arrival of living ungulates in South America around 2.5 million years ago as part of 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 land ...

. The bodyform of ''Macrauchenia'' has been described as similar to a camel, being one of the largest-known litopterns, with an estimated body mass of around 1 tonne. The genus gives its name to its family, Macraucheniidae, which like ''Macrauchenia'' typically had long necks and three-toed feet, as well as a retracted nasal region, which in ''Macrauchenia'' manifests as the nasal opening being on the top of the skull between the eye sockets. This has historically been argued to correspond to the presence of a tapir-like

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 arthropod mouthparts, mouthparts used for feeding and sucking. In vertebrates, a pr ...

, though recent authors suggest a moose-like prehensile lip or a saiga antelope-like nose to filter dust are more likely. Only one species is generally considered valid, ''M. patachonica'', which was described by

Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomy, comparative anatomist and paleontology, palaeontologist. Owen is generally considered to have been an outstanding naturalist with a remarkabl ...

based on remains discovered by

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English Natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all speci ...

during the voyage of the ''Beagle''. ''M. patachonica'' is primarily known from localities in the

Pampas The Pampas (; from Quechua 'plain'), also known as the Pampas Plain, are fertile South American low grasslands that cover more than and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all o ...

, but is known from remains found across the Southern Cone extending as far south as southernmost

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

, and as far north as Southern Peru. Another genus of macraucheniid '' Xenorhinotherium'' was present in northeast Brazil and Venezuela during the Late Pleistocene. ''Macrauchenia'' is thought to have been a mixed feeder that both consumed woody vegetation and grass that lived in herds and probably engaged in seasonal migrations. ''Macrauchenia'' is suggested to have been a swift runner that was capable of moving at considerable speed. ''Macrauchenia'' became extinct as part of the end-Pleistocene extinction event around 12,000 years ago, along with the vast majority of other large mammals native to the Americas. This followed the arrival of humans to the Americas, and possible evidence of human interactions with ''Macrauchenia'' has been found at a number of sites with some authors suggesting human hunting may have played a role in its extinction.

Taxonomy

''Macrauchenia'' fossils were first collected on 9 February 1834 at Port St Julian in southern

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

in what is now Argentina by

Charles Darwin Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English Natural history#Before 1900, naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all speci ...

, when HMS ''Beagle'' was surveying the port (the

Argentine Confederation The Argentine Confederation (Spanish: ''Confederación Argentina'') was the last predecessor state of modern Argentina; its name is still one of the official names of the country according to the Argentine Constitution, Article 35. It was the nam ...

claimed the region but did not effectively control it at the time). As a non-expert he tentatively identified the leg bones and fragments of spine he found as "some large animal, I fancy a

Mastodon A mastodon, from Ancient Greek μαστός (''mastós''), meaning "breast", and ὀδούς (''odoús'') "tooth", is a member of the genus ''Mammut'' (German for 'mammoth'), which was endemic to North America and lived from the late Miocene to ...

". In 1837, soon after the ''Beagle'' return, the anatomist

Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomy, comparative anatomist and paleontology, palaeontologist. Owen is generally considered to have been an outstanding naturalist with a remarkabl ...

identified the bones, including vertebrae from the back and neck, as from a gigantic creature resembling a

llama The llama (; or ) (''Lama glama'') is a domesticated South American camelid, widely used as a List of meat animals, meat and pack animal by Inca empire, Andean cultures since the pre-Columbian era. Llamas are social animals and live with ...

or

camel A camel (from and () from Ancient Semitic: ''gāmāl'') is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. Camels have long been domesticated and, as livestock, they provid ...

, which Owen named ''Macrauchenia patachonica''. In naming it, Owen noted the original Greek terms (, large or long) and (, neck), as used by Illiger as the basis of ''Auchenia'' as a generic name for the llama, ''

Vicugna ''Lama'' is a genus containing the South American camelids: the wild guanaco and vicuña and the domesticated llama, alpaca, and the extinct chilihueque. Before the Spanish conquest of the Americas, llamas, alpacas, and chilihueques were t ...

'' and so on. ''Macrauchenia patachonica'' is currently considered to be the only valid species of ''Macrauchenia''. ''Macrauchenia boliviensis'' from the probably early

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 ...

aged Kollukollu Formation of Bolivia described by Thomas Henry Huxley in 1860 is now considered to be an indeterminate member of Macraucheniidae. The species ''Macrauchenia ensenadensis'' described by

Florentino Ameghino Florentino Ameghino (born Giovanni Battista Fiorino Giuseppe Ameghino; September 19, 1853 – August 6, 1911) was an Argentine naturalist, paleontologist, anthropologist and zoologist, whose fossil discoveries on the Argentine Pampas, especial ...

in 1888 from the Early Pleistocene has been transferred to the closely related genus '' Macraucheniopsis''.

Evolution

''Macrauchenia'' is part of the extinct

ungulate Ungulates ( ) are members of the diverse clade Euungulata ("true ungulates"), which primarily consists of large mammals with Hoof, hooves. Once part of the clade "Ungulata" along with the clade Paenungulata, "Ungulata" has since been determined ...

order Litopterna, which is grouped with several other orders as part of the South American native ungulates (SANUs), which formed a conspicuous element of South America's Cenozoic mammal fauna beginning during the

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

, over 60 million years ago. Litopterns generally have body forms similar to those of living ungulates. The relationships of litopterns (as well as other SANUs) to living mammals was historically uncertain. Sequences of

mitochondrial DNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondrion, mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the D ...

extracted from remains of ''M. patachonica'' found in a cave in southern Chile published in 2017 indicates that the closest living relatives of ''Macrauchenia'' (and by inference, Litopterna) are members of the extant ungulate order Perissodactyla (which includes the equids,

rhinoceros A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...

es, and

tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a Suidae, pig, with a short, prehensile nose trunk (proboscis). Tapirs inhabit jungle and forest regions of South America, South and Centr ...

s), with litopterns estimated to have genetically diverged from perissodactyls around 66 million years ago. Analysis of collagen sequences obtained from ''Macrauchenia'' and the contemporaneous large rhinoceros-like South American ungulate '' Toxodon,'' which belongs to another SANU order, Notoungulata, in 2015 reached a similar conclusion and suggests that litopterns are more closely related to notoungulates than to perissodactyls. The earliest known fossils of litopterns are from the early Paleocene, around 62.5 million years ago. The family to which ''Macrauchenia'' belongs, Macraucheniidae, first appeared during the

Late Eocene The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...

or

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

, around 39-30 million years ago, depending on what species are included. Members of the family are typically characterised by having three-toed feet and long necks. The family reached its apex of diversity in the

Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...

, around 10-6 million years ago, before declining to low diversity during the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Pleistocene 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 ...

, as part of a broader decline of SANU diversity during this period. The cause of this diversity decline is uncertain, though it has been suggested to be due to climatic changes, as well as possibly competition/predation from immigrants from North America, who arrived following the formation of the

Isthmus of Panama The Isthmus of Panama, historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North America, North and South America. The country of Panama is located on the i ...

during the Pliocene as part of an event called 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 land ...

. The earliest fossils attributed to ''Macrauchenia'' date to the late

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58 though remains of ''Macrauchenia patachonica'' are primarily known from the

Late Pleistocene The Late Pleistocene is an unofficial Age (geology), age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a Stratigraphy, stratigraphic perspective. It is intended to be the fourth division ...

. Cladogram of Macraucheniidae after Lobo, Gelfo & Azevedo (2024):

Description

''Macrauchenia'' had a bodyform superficially like a camel, with a long neck composed of camel or giraffe-like elongated

cervical vertebrae In tetrapods, cervical vertebrae (: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In saurop ...

. In most of the cervical vertebrae, the canal for the artery passes through the neural arch. ''Macrauchenia'' was one of the largest macraucheniids and South American native ungulates, with an estimated body mass of around , considerably larger than earlier macraucheniids, which generally only weighed around .

Skull

The skull of ''Macrauchenia'' is relatively elongate and has an eye socket (

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

) entirely enclosed by bone, which is situated behind the teeth. Like other macraucheniids, there are a total of 44 teeth in the upper and lower jaws (the primitive number in placental mammals). The teeth form a continuous row on both jaws without any diastema (gaps) and they are all brachydont (low crowned). The most unusual feature of ''Macrauchenia'''s skull is its retracted nasal region, shared with other derived macraucheniines, which have the opening on the top of the skull roof between the eyesockets. Behind the nasal opening there is a substantially depressed region with numerous pits and ridges, which served as attachments for the nasal muscles. While historically this unusual nasal structure was taken as evidence for a

tapir Tapirs ( ) are large, herbivorous mammals belonging to the family Tapiridae. They are similar in shape to a Suidae, pig, with a short, prehensile nose trunk (proboscis). Tapirs inhabit jungle and forest regions of South America, South and Centr ...

-like probiscis/trunk, recent authors have expressed doubts about this, alternatively suggesting that it may have instead formed a

moose The moose (: 'moose'; used in North America) or elk (: 'elk' or 'elks'; used in Eurasia) (''Alces alces'') is the world's tallest, largest and heaviest extant species of deer and the only species in the genus ''Alces''. It is also the tal ...

-like prehensile lip, or a saiga antelope-like nasal structure which served to filter dust (which was likely prevalent in the environment where ''Macrauchenia'' lived), perhaps combining the function of dust filtering organ and a prehensile lip. Behind the nasal opening, the top of the skull shows the development of extensive sinuses.

Limbs

The

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

bone is very short and robust. The

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

and

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

in the forelimbs and the

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

and fibula in the hindlimbs are fused to each other, with the combined radius-ulna bone being broad in front view, and the fibula is much more slender than the tibia. The

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

has a well developed third trochanter, and is long relative to the length of the tibia. The forefeet and hindfeet each had three functional digits. The development of a suprapatellar fossa (an indentation) on the knee joint has led to suggestions that this functioned analogously to the stay apparatus found in living horses, allowing the knees to be passively locked while standing.

Distribution

Fossils of ''Macrauchenia'' are known from across the Southern Cone, ranging from northern Chile, southern Peru, southern Bolivia, and the

Pampas The Pampas (; from Quechua 'plain'), also known as the Pampas Plain, are fertile South American low grasslands that cover more than and include the Argentine provinces of Buenos Aires, La Pampa, Santa Fe, Entre Ríos, and Córdoba; all o ...

in Uruguay, northern Argentina and southern Brazil, southwards to extreme southernmost part of

Patagonia Patagonia () is a geographical region that includes parts of Argentina and Chile at the southern end of South America. The region includes the southern section of the Andes mountain chain with lakes, fjords, temperate rainforests, and glaciers ...

in southern Chile and Argentina. ''Macrauchenia'' is thought to have primarily inhabited arid, open environments with only scattered woody vegetation. A closely related genus, '' Xenorhinotherium'', inhabited more tropical environments in eastern Brazil and Venezuela.

Paleobiology

Macrauchenia patachonica Life Reconstruction

Analysis of dental calculus extracted from the teeth of an individual of ''Macrauchenia'' suggests that it was a mixed feeder (engaging in both

browsing Browsing is a kind of orienting strategy. It is supposed to identify something of relevance for the browsing organism. In context of humans, it is a metaphor taken from the animal kingdom. It is used, for example, about people browsing open sh ...

and

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 ...

), with this individual having a diet predominantly consisting of C₃ grasses. Dental microwear analysis of another individual also supports grazing being an important part of the diet for ''Macrauchenia.'' Like living perissodactyls, litopterns including ''Macrauchenia'' were probably hindgut fermenters. A 2022 study suggested that based on the anatomy of the cervical vertebrae ''Macrauchenia'' likely held its neck in an erect posture when at rest and browsing, similar to that of a llama, though the neck was highly flexible and able to adopt many postures including being lowered to the ground for feeding, as well as being able to flex side to side. Its elongated neck likely allowed it to efficiently browse vegetation without wasting energy. It has been speculated that ''Macrauchenia'' may have sometimes reared up onto its hind legs like a gerenuk when feeding. ''Macrauchenia'' is thought to have probably lived in herds, as evidenced by the finding of at least 3 individuals preserved together at the Kamac Mayu site in Chile, with herding individuals probably moving in coordination. ''Macrauchenia'' is suggested to have concentrated on foraging in small areas before swiftly moving on to other feeding areas. It has been suggested that ''Macrauchenia'' engaged in long distance seasonal migrations in search of food. Like living animals of similar size, it has been suggested that ''Macrauchenia'' probably only gave birth to a single offspring at a time. A 2020 study suggested that ''Macrauchenia'' was a capable and fast runner with fossilised footprints suggesting that its feet were held in a digitigrade stance, with the neck probably being held horizontally when running. The running style of ''Macrauchenia'' has been suggested to be similar to that of a saiga antelope or

spotted hyena The spotted hyena (''Crocuta crocuta''), also known as the laughing hyena, is a hyena species, currently classed as the sole extant member of the genus ''Crocuta'', native to sub-Saharan Africa. It is listed as being of least concern by the IUC ...

s, with a lack of flexing in the spine. A 2005 study suggested that ''Macrauchenia'' may have been adapted to swerving as a strategy of avoiding predators, based on the strength of the limb bones. The morphology of its hindlimbs suggests that they were adapted to rapidly accelerating, which may have been useful for both efficient locomotion and escaping predators. Isotopic analysis suggests that ''Macrauchenia'' was regularly consumed as prey by the large sabertooth cat '' Smilodon populator''.

Relationship with humans and extinction

''Macrauchenia'' became extinct as part of the end-Pleistocene extinction event at the end of the Late Pleistocene, around 12–10,000 years ago, along with most large (

megafauna In zoology, megafauna (from Ancient Greek, Greek μέγας ''megas'' "large" and Neo-Latin ''fauna'' "animal life") are large animals. The precise definition of the term varies widely, though a common threshold is approximately , this lower en ...

l) mammals native to the Americas. The extinctions followed the arrival of humans in the Americas, which in South America occurred at least 14,500 years ago (as evidenced by Monte Verde II in Chile). The causes of the extinction have long been controversial with human hunting and climatic change widely considered to be the most probable causes. Several potential instances of human interaction with ''Macrauchenia'' have been recorded. A left mandible collected from somewhere in the Pampas region in the 19th century in the collections of the '' Museum national d’Histoire naturelle'' in France has been suggested to display cut marks caused by human butchery, probably to extract the tongue. At Arroyo Seco 2 near Tres Arroyos in the Pampas in Argentina, bones of ''Macrauchenia'' amongst those of other megafauna were found associated with human artifacts dating to approximately 14,782–11,142 calibrated years

Before Present Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because ...

. While some megafauna remains at the site show clear evidence of exploitation, those of ''Macrauchenia'' do not, perhaps because post-depositional degradation of the bones may have erased cut marks. At the El Guanaco site in the Argentinean Pampas, remains of ''Macrauchenia'', alongside those of the glyptodont '' Doedicurus'', horses, and rhea eggshells are associated with stone tools. At the Paso Otero 5 site in the Pampas of northeast Argentina, burned bones of ''Macrauchenia'' alongside those of numerous other extinct megafauna species are associated with Fishtail points (a type of knapped stone spear point common across South America at the end of the Pleistocene, suggested to be used to hunt large mammals). The bones of the megafauna were probably deliberately burned as fuel. No cut marks are visible on the vast majority of bones at the site (with only one bone of a llama possibly displaying any butchery marks), which may be due to the burning degrading the bones.G. Martínez, M. A. Gutiérrez
Paso Otero 5: A summary of the interdisciplinary lines of evidence for reconstructing early human occupation and paleoenvironment in the Pampean region, Argentina
in ''Peuplements et Préhistoire de l’Amérique'', D. Vialou, Ed. (Muséum National d’ Histoire Naturelle. Departement de Prehistoire, U.M.R, Paris, 2011), pp. 271–284.

References

* * {{Taxonbar, from=Q139086 Macraucheniids Messinian first appearances Holocene extinctions Miocene mammals of South America Pliocene mammals of South America Pleistocene mammals of South America Lujanian Ensenadan Uquian Chapadmalalan Montehermosan Huayquerian Neogene Argentina Cerro Azul Formation Pleistocene Argentina Pleistocene Bolivia Pleistocene Brazil Pleistocene Chile Pleistocene Paraguay Pleistocene Peru Dolores Formation, Uruguay Pleistocene Venezuela Fossils of Argentina Fossils of Bolivia Fossils of Brazil Fossils of Chile Fossils of Paraguay Fossils of Peru Fossils of Uruguay Fossils of Venezuela Fossil taxa described in 1838 Taxa named by Richard Owen Prehistoric placental genera Sopas Formation