Sloth
Overview
 
Sloths are the six species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of medium-sized mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s belonging to the families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Megalonychidae
Two-toed sloth
Choloepus is a genus of mammals of Central and South America, within the family Megalonychidae consisting of two-toed sloths. There are only two species of Choloepus : Linnaeus's Two-toed Sloth and Hoffmann's Two-toed Sloth...

 (two-toed sloth) and Bradypodidae
Three-toed sloth
The three-toed sloths are tree-living mammals from South and Central America. They are the only members of the genus Bradypus and the family Bradypodidae. There are four living species of three-toed sloths...

 (three-toed sloth), part of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Pilosa
Pilosa
The order Pilosa is a group of placental mammals, extant today only in the Americas. It includes the anteaters and sloths, including the recently extinct ground sloths....

 and therefore related to armadillo
Armadillo
Armadillos are New World placental mammals, known for having a leathery armor shell. Dasypodidae is the only surviving family in the order Cingulata, part of the superorder Xenarthra along with the anteaters and sloths. The word armadillo is Spanish for "little armored one"...

s and anteater
Anteater
Anteaters, also known as antbear, are the four mammal species of the suborder Vermilingua commonly known for eating ants and termites. Together with the sloths, they compose the order Pilosa...

s, which sport a similar set of specialized claws.

They are arboreal
Arboreal locomotion
Arboreal locomotion is the locomotion of animals in trees. In every habitat in which trees are present, animals have evolved to move in them. Some animals may only scale trees occasionally, while others are exclusively arboreal. These habitats pose numerous mechanical challenges to animals...

 (tree dwelling) residents of the jungles
Tropical rainforest
A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...

 of Central
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

 and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

.
The sloth's taxonomic suborder
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

 is Folivora, while some call it Phyllophaga.
Encyclopedia
Sloths are the six species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 of medium-sized mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s belonging to the families
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Megalonychidae
Two-toed sloth
Choloepus is a genus of mammals of Central and South America, within the family Megalonychidae consisting of two-toed sloths. There are only two species of Choloepus : Linnaeus's Two-toed Sloth and Hoffmann's Two-toed Sloth...

 (two-toed sloth) and Bradypodidae
Three-toed sloth
The three-toed sloths are tree-living mammals from South and Central America. They are the only members of the genus Bradypus and the family Bradypodidae. There are four living species of three-toed sloths...

 (three-toed sloth), part of the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Pilosa
Pilosa
The order Pilosa is a group of placental mammals, extant today only in the Americas. It includes the anteaters and sloths, including the recently extinct ground sloths....

 and therefore related to armadillo
Armadillo
Armadillos are New World placental mammals, known for having a leathery armor shell. Dasypodidae is the only surviving family in the order Cingulata, part of the superorder Xenarthra along with the anteaters and sloths. The word armadillo is Spanish for "little armored one"...

s and anteater
Anteater
Anteaters, also known as antbear, are the four mammal species of the suborder Vermilingua commonly known for eating ants and termites. Together with the sloths, they compose the order Pilosa...

s, which sport a similar set of specialized claws.

They are arboreal
Arboreal locomotion
Arboreal locomotion is the locomotion of animals in trees. In every habitat in which trees are present, animals have evolved to move in them. Some animals may only scale trees occasionally, while others are exclusively arboreal. These habitats pose numerous mechanical challenges to animals...

 (tree dwelling) residents of the jungles
Tropical rainforest
A tropical rainforest is an ecosystem type that occurs roughly within the latitudes 28 degrees north or south of the equator . This ecosystem experiences high average temperatures and a significant amount of rainfall...

 of Central
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

 and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

.

Taxonomy and names

The sloth's taxonomic suborder
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

 is Folivora, while some call it Phyllophaga. Both names mean "leaf-eaters"; derived from Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 and Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 respectively. Names for the animals used by tribes in Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...

 include Ritto, Rit and Ridette, mostly forms of the word "sleep", "eat" and "dirty" from Tagaeri
Tagaeri
The Tagaeri are a clan of Huaorani people living in Yasuni National Park, at the Ecuadorian Amazon Basin, named for their association with the warrior Taga...

 tribe of Huaorani
Huaorani
The Huaorani, Waorani or Waodani, also known as the Waos, are native Amerindians from the Amazonian Region of Ecuador who have marked differences from other ethnic groups from Ecuador. The alternate name Auca is a pejorative exonym used by the neighboring Quechua Indians, and commonly adopted by...

.

Ecology

Sloths are classified as folivore
Folivore
In zoology, a folivore is a herbivore that specializes in eating leaves. Mature leaves contain a high proportion of hard-to-digest cellulose, less energy than other types of foods, and often toxic compounds. For this reason folivorous animals tend to have long digestive tracts and slow metabolisms....

s as the bulk of their diet consists mostly of buds, tender shoots, and leaves, mainly of Cecropia
Cecropia
Cecropia is a Neotropical genus presently consisting of sixty-one recognized species with a highly distinctive lineage of dioecious trees....

trees. Some two-toed sloths have been documented as eating insect
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, small reptiles and birds as a small supplement to their diet. Linnaeus's Two-toed Sloth
Linnaeus's Two-toed Sloth
Linnaeus's two-toed sloth , also known as the Southern two-toed sloth or unau, is a species of sloth from South America, found in Venezuela, the Guyanas, Colombia, Ecuador, Peru and Brazil north of the Amazon River....

 has recently been documented eating human feces from open latrines. They have made extraordinary adaptations to an arboreal browsing lifestyle. Leaves, their main food source, provide very little energy or nutrition and do not digest easily. Sloths therefore have large, specialized, slow-acting stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...

s with multiple compartments in which symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 break down the tough leaves. As much as two-thirds of a well-fed sloth's body-weight consists of the contents of its stomach, and the digestive process can take a month or more to complete.

Even so, leaves provide little energy, and sloths deal with this by a range of economy measures: they have very low metabolic
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 rates (less than half of that expected for a mammal of their size), and maintain low body temperatures when active (30–34 °C or 86–93 °F), and still lower temperatures when resting.

Although unable to survive outside the tropical rainforests of South and Central America, within that environment sloths are outstandingly successful creatures: they can account for as much as half the total energy consumption and two-thirds of the total terrestrial mammalian biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 in some areas. Four of the six living species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 are presently rated "least concern"; the Maned Three-toed Sloth
Maned Three-toed Sloth
The maned sloth , also known as the ai , is a three-toed sloth that lives only in Brazil. It is one of only four species of three-toed sloth.-Distribution and habitat:...

 (Bradypus torquatus), which inhabits Brazil's dwindling Atlantic Forest, is classified as "endangered", while the island-dwelling Pygmy Three-toed Sloth (B. pygmaeus) is critically endangered.

Physiology

Sloth furs exhibit specialized functions: the outer hairs grow in a direction opposite from that of other mammals. In most mammals hairs grow toward the extremities, but because sloths spend so much time with their legs above their bodies, their hairs grow away from the extremities in order to provide protection from the elements while the sloth hangs upside down. In most conditions, the fur hosts two species of symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...

 cyanobacteria, which provide camouflage. Because of the cyanobacteria, sloth fur is a small ecosystem of its own, hosting many species of non-parasitic insects. Sloths have short, flat heads; big eyes; a short snout; long legs; and tiny ears. They might have stubby tails (6–7 cm long), but not in all species. Altogether, sloths' bodies usually are anywhere between 50 and 60 cm long.

Sloths' claws serve as their only natural defense. A cornered sloth may swipe at its attackers in an effort to scare them away or wound them. Despite sloths' apparent defenselessness, predators do not pose special problems: sloths blend in with the trees and, moving only slowly, do not attract attention. Only during their infrequent visits to ground level do they become vulnerable. The main predators of sloths are the jaguar
Jaguar
The jaguar is a big cat, a feline in the Panthera genus, and is the only Panthera species found in the Americas. The jaguar is the third-largest feline after the tiger and the lion, and the largest in the Western Hemisphere. The jaguar's present range extends from Southern United States and Mexico...

, the harpy eagle
American Harpy Eagle
The Harpy Eagle , sometimes known as the American Harpy Eagle, is a Neotropical species of eagle. It is the largest and most powerful raptor found in the Americas, and among the largest extant species of eagles in the world. It usually inhabits tropical lowland rainforests in the upper canopy layer...

, and humans. The majority of recorded sloth deaths in Costa Rica are due to contact with electrical lines
Electric power transmission
Electric-power transmission is the bulk transfer of electrical energy, from generating power plants to Electrical substations located near demand centers...

 and poachers
Poaching
Poaching is the illegal taking of wild plants or animals contrary to local and international conservation and wildlife management laws. Violations of hunting laws and regulations are normally punishable by law and, collectively, such violations are known as poaching.It may be illegal and in...

. Despite their adaptation to living in trees, sloths make competent swimmers. Their claws also provide a further unexpected deterrent to human hunters: when hanging upside-down in a tree they are held in place by the claws themselves and often do not fall down even if shot from below.
Sloths move only when necessary and even then very slowly: they have about a quarter as much muscle tissue as other animals of similar weight. They can move at a marginally higher speed if they are in immediate danger from a predator (4 m or 13 feet per minute for the three-toed sloth), but they burn large amounts of energy doing so. Their specialized hands and feet have long, curved claws to allow them to hang upside-down from branches without effort. While they sometimes sit on top of branches, they usually eat, sleep, and even give birth hanging from limbs. They sometimes remain hanging from branches after death. On the ground the maximum speed of the three-toed sloth is 2 m or 6.5 feet per minute.

It had been thought that sloths were among the most somnolent
Somnolence
Somnolence is a state of near-sleep, a strong desire for sleep, or sleeping for unusually long periods . It has two distinct meanings, referring both to the usual state preceding falling asleep, and the chronic condition referring to being in that state independent of a circadian rhythm...

 animals, sleeping from 15 to 18 hours each day. Recently, however, Dr. Neil Rattenborg and his colleagues from the Max Planck Institute for Ornithology in Starnberg, Germany, published a study testing sloth sleep-patterns in the wild; this is the first study of its kind. The study indicated that sloths sleep just under 10 hours a day.

They go to the ground to urinate and defecate about once a week, digging a hole and covering it afterwards. They go to the same spot each time and are vulnerable to predation while doing so. The reason for this risky behavior is unknown, although some believe that this is to avoid making noise while defecating from up high that would attract predators. Consistent with this, they reportedly relieve themselves from their branches during storms in rainy season. Another possible explanation is that the middens provide the sloths with one of their few methods of finding one another for breeding purposes, since their sense of smell is far more acute than their eyesight or hearing. It has also been pointed out that individual sloths tend to spend the bulk of their time feeding on a single "modal" tree; by burying their excreta near the trunk of that tree, they may help nourish it.

Infant sloths normally cling to their mothers' fur, but occasionally fall off. Sloths are very sturdily built and rarely die from a fall. In some cases they die from a fall indirectly because the mothers prove unwilling to leave the safety of the trees to retrieve the young. Females normally bear one baby every year, but sometimes sloths' low level of movement actually keeps females from finding males for longer than one year.

Almost all mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s have seven cervical vertebrae
Cervical vertebrae
In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...

 or "neck bones" (including those with very short necks, such as elephant
Elephant
Elephants are large land mammals in two extant genera of the family Elephantidae: Elephas and Loxodonta, with the third genus Mammuthus extinct...

s or whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...

s, and those with very long necks, such as giraffe
Giraffe
The giraffe is an African even-toed ungulate mammal, the tallest of all extant land-living animal species, and the largest ruminant...

s). The few exceptions include manatee
Manatee
Manatees are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows...

s and two-toed sloths, which each have only six cervical vertebrae, and three-toed sloths with nine cervical vertebrae.

Evolution

Sloths are members of the superorder Xenarthra
Xenarthra
The superorder Xenarthra is a group of placental mammals , existent today only in the Americas and represented by anteaters, tree sloths, and armadillos. The origins of the order can be traced back as far as the Paleogene in South America...

, a group of mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s that appeared approximately 60 million years ago, although at least one source puts the date at which sloths and related animals broke off from other placental mammals at about 100 million years ago. Also included among the Xenarthra are anteaters and armadillos. The earliest xenarthrans were arboreal
Arboreal locomotion
Arboreal locomotion is the locomotion of animals in trees. In every habitat in which trees are present, animals have evolved to move in them. Some animals may only scale trees occasionally, while others are exclusively arboreal. These habitats pose numerous mechanical challenges to animals...

 herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

s with sturdy spines, fused pelvises, stubby teeth and small brains.

The living sloths belong to one of two families, known as the Megalonychidae ("two-toed" sloths) and the Bradypodidae (three-toed sloths). All living sloths have in fact three toe
Toe
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of...

s; the "two-toed" sloths, however, have only two finger
Finger
A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....

s. Two-toed sloths are generally faster moving than three-toed sloths. Both types tend to occupy the same forests: in most areas, one species of three-toed sloth and one species of the larger two-toed type will jointly predominate.

However, their adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....

s belie the actual relationships of the living sloth genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

, which are more distant from each other than their outward similarity suggests. The common ancestor of the two genera apparently lived 35–40 million years ago, making the living forms stunning examples of convergent
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...

 or parallel evolution
Parallel evolution
Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...

. The two-toed sloths of today are far more closely related to one particular group of ground sloths than to the living three-toed sloths. Whether these ground-dwelling Megalonychidae were descended from tree-climbing ancestors or whether the two-toed sloths are really miniature ground sloths converted (or reverted) to arboreal life cannot presently be determined to satisfaction. The latter possibility seems slightly more likely, given the fact that the small ground sloths Acratocnus
Acratocnus
Acratocnus is an extinct genus of ground sloth found in Cuba, Hispaniola and Puerto Rico.-Classification:Like all of the Antillean sloths, Acratocnus is a member of the family Megalonychidae, whose sole surviving genus is Choloepus, representing the two-toed tree sloths.-Location:The species of...

and Neocnus which were also able to climb are among the closer relatives of the two-toed sloths, and that these together were related to the huge ground sloths Megalonyx and Megalocnus
Megalocnus
The ground sloths of the extinct genus Megalocnus were among the largest of the Caribbean ground sloths, with individuals estimated to have weighed up to when alive. Two species are known, M. rodens of Cuba, and M. zile of Hispaniola. Subfossils of M...

.

The evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

ary history of the three-toed sloths is not well known. No particularly close relatives, ground-dwelling or not, have yet been identified.

The ground sloths do not constitute a monophyletic
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

 group. Rather, they make up a number of lineages, and as far as is known until the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...

 most sloths were in fact ground-dwellers. The famous Megatherium
Megatherium
Megatherium was a genus of elephant-sized ground sloths endemic to Central America and South America that lived from the Pliocene through Pleistocene existing approximately...

, for example, belonged to a lineage of ground sloths that was not very close to the living sloths and their ground-living relatives, like the small Neocnus or the massive Megalonyx. Meanwhile, Mylodon
Mylodon
Mylodon is an extinct genus of giant ground sloth that lived in the Patagonia area of South America until roughly 10,000 years ago.Mylodon weighed about and stood up to tall when raised up on its hind legs. Preserved dung has shown it was a herbivore. It had very thick hide and had osteoderms...

, among the last ground sloths to disappear, was only very distantly related to either of these.

Classification

Suborder Folivora (sloths)
  • Family Bradypodidae (Three-toed sloth
    Three-toed sloth
    The three-toed sloths are tree-living mammals from South and Central America. They are the only members of the genus Bradypus and the family Bradypodidae. There are four living species of three-toed sloths...

    s)
    • Bradypus
      • Pale-throated Sloth (Bradypus tridactylus))
      • Brown-throated Sloth (Bradypus variegatus)
      • Maned Sloth (Bradypus torquatus)
      • Pygmy Three-toed Sloth
        Pygmy Three-toed Sloth
        The Pygmy Three-toed Sloth is a three-toed sloth. It is endemic to Isla Escudo de Veraguas, an island off the coast of Panama, which separated from the mainland nearly 8900 years ago. The species is thought to have originated from isolation of individuals from the mainland population of Bradypus...

         (Bradypus pygmaeus)
  • Family Megalonychidae
    Megalonychidae
    Megalonychidae is a group of sloths including the extinct Megalonyx and the living two toed sloths. Megalonychids first appeared in the early Oligocene, about 35 million years ago, in southern Argentina , and spread as far as the Antilles by the early Miocene...

     (two-toed sloths and extinct ground sloths)
    • Choloepus (Two-toed sloth
      Two-toed sloth
      Choloepus is a genus of mammals of Central and South America, within the family Megalonychidae consisting of two-toed sloths. There are only two species of Choloepus : Linnaeus's Two-toed Sloth and Hoffmann's Two-toed Sloth...

      s)
      • Hoffmann's Two-toed Sloth
        Hoffmann's Two-toed Sloth
        Hoffmann's two-toed sloth is a species of sloth from Central and South America. It is a solitary nocturnal and arboreal animal, found in mature and secondary rainforests and deciduous forests...

         (Choloepus hoffmanni)
      • Linnaeus's Two-toed Sloth
        Linnaeus's Two-toed Sloth
        Linnaeus's two-toed sloth , also known as the Southern two-toed sloth or unau, is a species of sloth from South America, found in Venezuela, the Guyanas, Colombia, Ecuador, Peru and Brazil north of the Amazon River....

         (Choloepus didactylus)
    • Acratocnus
      Acratocnus
      Acratocnus is an extinct genus of ground sloth found in Cuba, Hispaniola and Puerto Rico.-Classification:Like all of the Antillean sloths, Acratocnus is a member of the family Megalonychidae, whose sole surviving genus is Choloepus, representing the two-toed tree sloths.-Location:The species of...

    • Habanocnus
      Habanocnus
      theyHabanocnus is an extinct genus of ground sloth indigenous to Late Pleistocene Cuba. It was related to the genus Megalocnus...

    • Neocnus
    • Imagocnus
      Imagocnus
      Imagocnus is an extinct genus of ground sloth from the early Miocene of Cuba.This sloth resided in the Antilles and showed a range of body size. Its relationships to other Antillean sloths are not immediately clear, though the genera Megalocnus and Parocnus,other ground sloths, are its most likely...

    • Megalocnus
      Megalocnus
      The ground sloths of the extinct genus Megalocnus were among the largest of the Caribbean ground sloths, with individuals estimated to have weighed up to when alive. Two species are known, M. rodens of Cuba, and M. zile of Hispaniola. Subfossils of M...

    • Megalonyx
      Megalonyx
      Megalonyx is an extinct genus of giant ground sloths of the family Megalonychidae endemic to North America from the Hemphillian of the Late Miocene through to the Rancholabrean of the Pleistocene, living from ~10.3 Mya—11,000 years ago, existing for approximately .-Taxonomy:The generic name...

  • Family Megatheriidae
    Megatheriidae
    Megatheriidae is a family of extinct ground sloths that lived from approximately 23 mya—11,000 years ago, existing for approximately .Megatheriids appeared later in the Oligocene, some 30 million years ago, also in South America. The group includes the heavily-built Megatherium and Eremotherium...

     (megatheriid ground sloths)
    • Eremotherium
      Eremotherium
      Eremotherium is an extinct genus of actively mobile ground sloth of the family Megatheriidae, endemic to North America and South America during the Pleistocene epoch...

    • Hapalops
      Hapalops
      Hapalops is an extinct genus of ground sloth from the late Oligocene of South America.Though related to the giant Megatherium, Hapalops was much smaller, measuring about in length. Like most extinct sloths it is categorized as a ground sloth, but it is believed that the smaller size of Hapalops...

    • Megatherium
      Megatherium
      Megatherium was a genus of elephant-sized ground sloths endemic to Central America and South America that lived from the Pliocene through Pleistocene existing approximately...

    • Nothropus
      Nothropus
      Nothropus is an extinct genus of actively mobile ground sloth of the family Megatheriidae, endemic to South America during the Pleistocene epoch. It lived from 1.8 mya—78,000 years ago existing for approximately .-Taxonomy:...

  • Family Mylodontidae
    Mylodontidae
    Mylodontidae is a family of extinct mammals within the order of Pilosa and suborder Folivora living from approximately 23 mya—11,000 years ago, existing for approximately . This family of ground sloths is related to the other families of extinct ground sloths, being the Megatheriidae, the...

     (mylodontid ground sloths)
    • Glossotherium
      Glossotherium
      Glossotherium was a genus of ground sloth. It was a heavily built animal with a length of about snout to tail-tip, and could potentially assume a slight bipedal stance.Fossils of this animal have been found in South America...

    • Lestodon
      Lestodon
      Lestodon is an extinct genus of ground sloth from South America. The etymology of the name means "robber tooth." Lestodon is placed as member of the Mylodontidae as indicated by the lobed form of the last tooth in the dentition.-External links:*...

    • Mylodon
      Mylodon
      Mylodon is an extinct genus of giant ground sloth that lived in the Patagonia area of South America until roughly 10,000 years ago.Mylodon weighed about and stood up to tall when raised up on its hind legs. Preserved dung has shown it was a herbivore. It had very thick hide and had osteoderms...

    • Paramylodon
      Paramylodon
      Paramylodon is an extinct genus of ground sloth of the family Mylodontidae endemic to North America during the Pliocene through Pleistocene epochs, living from around ~4.9 Mya—11,000 years ago .-Overview:...

    • Scelidotherium
      Scelidotherium
      Scelidotherium is an extinct genus of actively mobile ground sloth of the family Mylodontidae, endemic to South America during the middle Pleistocene epoch. It lived from 780,000—11,000 years ago, existing for approximately ....

    • Chubutherium
      Chubutherium
      Chubutherium ferelloii is an extinct species of ground sloth .This species of ground sloth shared many of the traits with members of the Mylodontidae family. C. ferelloii first appeared in the Oligocene and died out during the Middle Miocene. It is related to the Pleistocene genus, Scelidotherium....

  • Family Nothrotheriidae (nothrotheriid ground sloths)
    • Nothrotheriops
      Nothrotheriops
      Nothrotheriops is a genus of Pleistocene ground sloth found in North and South America. This genus of bear-sized xenarthran was related to the much larger, and far more famous Megatherium, although it has recently been placed in a different family, Nothrotheriidae.-Discovery and species:Fossils of...

    • Nothrotherium
      Nothrotherium
      Nothrotherium is an extinct genus of ground sloth from South America....

    • Thalassocnus
      Thalassocnus
      Thalassocnus is an extinct genus of semi-aquatic or aquatic marine sloth from the Miocene and Pliocene of South America. Fossils found to date have been from the coast of Peru. They were apparently grazers of sea grass and seaweed. Over time, they apparently shifted from a preference for feeding...

  • Family Orophodontidae
    Orophodontidae
    Orophodontidae is a family of extinct ground sloths within the order of Pilosa and suborder Folivora. The name is often disused with genus members reassigned....

     (orophodontid ground sloths)

Extinction

Until geologically recent times, ground sloth
Ground sloth
Ground sloths are a diverse group of extinct sloths, in the mammalian superorder Xenarthra. Their most recent survivors lived in the Antilles, where it has been proposed they may have survived until 1550 CE; however, the youngest AMS radiocarbon date reported is 4190 BP, calibrated to c. 4700 BP...

s such as Megatherium
Megatherium
Megatherium was a genus of elephant-sized ground sloths endemic to Central America and South America that lived from the Pliocene through Pleistocene existing approximately...

lived in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 and parts of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

, but along with many other animals they disappeared immediately after the arrival of humans on the continent. Much evidence suggests that human hunting contributed to the extinction of the American megafauna
Megafauna
In terrestrial zoology, megafauna are "giant", "very large" or "large" animals. The most common thresholds used are or...

, like that of far northern Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

, and Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...

. Simultaneous climate change that came with the end of the last Ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...

 may have also played a role in some cases. However, the fact that ground sloths survived
Megalocnus
The ground sloths of the extinct genus Megalocnus were among the largest of the Caribbean ground sloths, with individuals estimated to have weighed up to when alive. Two species are known, M. rodens of Cuba, and M. zile of Hispaniola. Subfossils of M...

 on the Antilles
Antilles
The Antilles islands form the greater part of the West Indies in the Caribbean Sea. The Antilles are divided into two major groups: the "Greater Antilles" to the north and west, including the larger islands of Cuba, Jamaica, Hispaniola , and Puerto Rico; and the smaller "Lesser Antilles" on the...

 long after they had died out on the mainland points toward human activities as the agency of extinction.

External links

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