The leaves in addition, are toxic and very difficult to digest and assimilate into the body: part of the reason why sloths have one of the slowest metabolic and digestive rates. Two toed sloths eat mostly by hanging horizontally upside down from tree branches. Powered by Create your own unique website with customizable templates.
- A Sloths Digestive System Homeostasis
- Sloth Body Parts
- A Sloths Digestive System Functions
- Digestive System Steps
- CLASS: Mammalia (Mammals)
- ORDER: Pilosa
- FAMILY: Megalonychidae
- GENUS:Choloepus
- SPECIES:hoffmanni (Hoffman's two-toed sloth) and didactylus (Linné's two-toed sloth)
'Leaf it' to the sloth: Thousands of years ago, large ground sloths roamed the United States. They ranged in size from an average-size dog to that of an elephant. These ground sloths had long claws and ate plants. They became extinct about 10,000 years ago. Present-day sloths are much smaller, and live in trees. The anteater is their closest relative.
In a nutshell, sloths are slow-moving, nocturnal creatures that spend almost their entire life upside down in the trees. They eat, sleep, mate, and give birth from this position hanging high among the branches. Sloths are the only mammals whose hair grows in the opposite direction from the hair of other mammals. To accommodate their upside lifestyle, the hair parts in the middle of the belly and grows upward toward the back. The hair on the face points upward, too. This allows water to run off during rainstorms!
Each strand of sloth fur has grooves that collect algae, giving sloths a greenish tint. That helps them blend into the trees they call home. The algae also provides nutrients for the sloth when nibbling on the hair during grooming. The only time sloths descend to the forest floor is to poop, which they do about once a week. To move to a new area of trees, sloths often wait for the forest to flood and then swim to their next home.
Big forest cats like jaguars and ocelots, birds of prey such as harpy eagles, and large snakes like anacondas prey upon sloths. They defend themselves with their sharp claws and teeth. And, if needed, sloths can move quickly through the trees.
If our own body temperature changes more than five degrees, it means we are sick! The two-toed sloth is different. It has the lowest and most variable body temperature of any mammal, ranging from 74 to 92 degrees Fahrenheit (24 to 33 degrees Celsius). If there is a long period of cool, rainy weather, a nursing female can get too cold. This causes the bacteria in her stomach to stop working, so the mother can no longer digest her food. The young continues to nurse as its mother starves to death. This chilling phenomenon is called cold-weather orphan syndrome, as sometimes the youngster falls to the ground and needs to be rescued by humans.
Sloths live in trees in the tropical and cloud forests of Central and South America. Their curved, sharp claws are 3 to 4 inches (8 to 10 centimeters) long. These claws are handy for hanging onto tree branches but make walking on the ground awkward. Yet sloths are great swimmers and can drop from a tree into a river to swim across it while doing the breaststroke! When sleeping, sloths often curl up in a ball in the fork of a tree.
With a muscle mass of only 25 percent (most mammals have twice as much), sloths can't shiver when it's cold. But they weigh much less than other animals their size, which is helpful for life in the trees. Sloths can grab the leaves and shoots on high, narrow branches that other animals can't reach. Two-toed sloths have two toes with claws on the front feet and three toes on the back feet, used to hang upside down from branches. (Three-toed sloths have three toes on their front AND back feet.)
Sloths look like some kind of slow-motion monkey and have long had a reputation for being lazy. The reason they move so slowly has a lot to do with what they eat: a variety of leaves, stems, buds, and some fruit. This kind of diet requires a special digestive system. Sloths have a large, four-chambered stomach, like a cow. Bacteria in their gut help digest the large amount of plant matter they eat. Due to the low nutritional value of their leafy diet, sloths usually move at a leisurely pace and sleep a great deal. They sleep 15 to 18 hours per day and (slowly) look for food at night. Even their innards move slowly, and some food items can take an entire month to digest! This slow metabolism helps sloths survive injuries that would kill other animals.
At the San Diego Zoo, our two-toed sloths eat low-starch, high-fiber biscuits, fresh fruits and veggies, and a variety of fresh browse.
SaveSave
Sloth romance:These ponderous animals spend most of their time alone. But when a female is ready to breed, she lets out a nighttime 'scream' that alerts any interested males. If more than one male reaches her at the same time, they slowly fight each other while hanging by their rear legs! Winner takes all, and several months later, the female gives birth (while upside down) to a single offspring.
The youngster must grab onto its mother's hair at birth and find its way to her nipples to nurse. The mother's body position looks like a comfortable hammock of sorts as baby rests on her chest. The baby begins sampling solid foods at about 10 days but still nurses for about a month. After that, the youngster continues to cling to its mother's belly but eats whatever she eats. It first hangs upside down on its own at 20 to 25 days.
The sloth youngster stays with its mother for six months to two years, depending on the subspecies. It then 'branches off' to live on its own. The young inherits a part of the home range left vacant by the mother, as well as her taste for certain leaves. Several sloths can live in a similar home range without competing for food or space.
A sloth's voice sounds like the hiss of a deflating balloon, but the animal can also squeal and grunt as needed. A low bleat signals distress—sloth ears are most tuned to low-frequency sounds. The sloth has an excellent sense of smell. Males scent mark on tree branches from a gland on the rump.
SaveSave
We exhibited two-toed sloths in our early years, but without much success. In the early 1930s, we managed to keep a mother and her baby alive for three years.
A Sloths Digestive System Homeostasis
Today, we have several Linné's two-toed sloths at the Zoo and the Safari Park, serving as animal ambassadors for their species. Xena, born at the Zoo in 2013, meets guests up close during special animal presentations—and occasionally she is joined by her new baby, born in April 2019. The baby's father is another animal ambassador—a handsome male sloth named Brad Pitt.
Though not uncommon in the wild, deforestation and other forms of habitat destruction remain threats for the sloth.Other human-made threats include power lines and roads. Educating children and adults in the sloths' home countries about the animals' importance to the ecosystem—and how to treat sloths respectfully—remains a challenge for those who want to help this unique and wonderful animal.
Both two-toed sloth species live in zoos. Yet identifying the two has always been problematic—they look alike! Based on the genetic information, a senior research associate in our Genetics Division designed a low-cost, easy-to-use genetic tool to identify two-toed sloths and improve management of the captive population. This tool allows visualizing DNA differences between species in a polymer matrix, a procedure that uses non-sophisticated tools in simple laboratory settings.
You can help us bring sloths and other species back from the brink by supporting the San Diego Zoo Global Wildlife Conservancy. Together we can save and protect wildlife around the globe.
Everybody loves sloths, and whenever we talk about sloths we have to remember that the two living kinds (Bradypus – the four species of three-toed sloth – and Choloepus – the two species of two-toed sloth) are but the tip of the iceberg when it comes to sloth diversity. This article – an excerpt from Naish (2005) (though with citations added that were absent in the published article) – briefly reviews the anatomy of fossil sloths, though there are references to the living forms where appropriate.
A typical fossil sloth can be imagined as a rather bear-shaped, shaggy-furred mammal with particularly powerful forelimbs, a barrel-shaped ribcage, a stout tail, prominent curved hand and foot claws and a markedly broad, robust pelvis.
Sloth skulls are diverse in form and range from the deep and broad, snub-faced morphology seen in Bradypus and some megalonychids to the elongate almost horse-like skulls of megatheriids and others (Gaudin 2004). Some megalonychids had a domed cranium resulting from marked enlargement of the sinuses within the frontal bones. The sloth palate is rugose and covered in pits and grooves and there are distinctive deep laminae that descend ventrally from the pterygoid bones (Gaudin 2004). The tip of the sloth mandible is usually spout-shaped and there is a foramen, representing an external opening of the mandibular canal, on the side of the lower jaw. In sloths with particularly long-rooted teeth there is a distinct bulge on the ventral margin of the lower jaw.
Sloths have peculiar teeth. They do not possess deciduous teeth but have a single set of high-crowned, open-rooted teeth (Bargo et al. 2006) that grow continuously throughout life, and the lack of a replacement dentition has made it difficult to homologise sloth teeth with those of other mammals. Incisors are absent, and it is not really possible to distinguish between the similar premolars and molars. The living tree sloth Choloepus, as well as some mylodontids, megalonychids and nothrotheriids, possess caniniform teeth separated from the other teeth by a diastema. The upper caniniforms of these sloths are ahead of the lower caniniforms and, while some evidence suggests that the upper caniniform in Choloepus is a true canine, this probably isn't the case for the lower caniniform. In the Pleistocene megalonychid Megalocnus from Cuba, and in certain other genera, the two most anterior upper jaw teeth have been described as ‘pseudorodentiform' and are more incisiform than caniniform.
Sloth teeth lack enamel and are composed instead of two different kinds of dentine plus an outer layer of cementum, the softer dentine forming the innermost region of the tooth. When sloth teeth erupt they are devoid of the cusps and basins seen normally in mammalian teeth and are simple and cylindrical in form. As the teeth occlude against those in the opposite jaw, valleys and cusp-like structures are formed as the two kinds of dentine erode differentially (Naples 1989, 1995). Some fossil sloths had squarish or subrectangular teeth and, in these forms, transverse ridges between the valleys are particularly prominent.
Arms, hands and hips
The forelimbs of most sloths are about subequal in length to the hindlimbs, the most prominent exceptions being the long-armed tree sloths of the genus Bradypus. Mylodontids had a particularly prominent olecranon process on the ulna. Recent studies have shown that the length of the olecranon process relative to the rest of the ulna is a good indicator of digging ability in mammals as the olecranon provides the attachment area for the triceps, the main muscle used in digging. Forelimb bone strength in mylodontids was also high and shows that the forelimbs were resistant to impact with the ground (Bargo et al. 2000). Furthermore, the wide, straight and relatively flat claws of these sloths resemble those of living mammals that dig. Accordingly, mylodontids seem to have been proficient diggers that unearthed roots and tubers and they may even have constructed burrows.
Sloths are amazingly diverse and unusual in hand morphology. Among megatheriids, primitive species of Eremotherium were pentadactyl (albeit it with a short thumb and a fifth digit with only one phalanx) while the advanced species E. laurillardi was tridactyl, possessing only digits III-V, and of these only digits III and IV had unguals (Cartelle & De Iuliis 1995).
Bradypus, a taxon that's notable for being outside the clade that includes the majority of other sloth lineages (Gaudin 2004, Pujos et al. 2007), possesses only digits II-IV on the hand, and the megalonychid Choloepus only has II and III. Several sloth groups exhibit fusion of various manual phalanges, including of both phalanges in the thumb (in Eremotherium) and of the two phalanges at the base of the third digit (in Thalassocnus), as well as fusion of metacarpals to carpals.
The sloth pelvis is massive and broad and unusual in that the ischia are connected to the vertebral column (in most tetrapods only the ilia are connected), a feature that sloths share with all other xenarthrans with the sole exception of Cyclopes, the Pygmy anteater. The femur in fossil sloths varies from robust to very robust with the femora of giant megatheriids being shaped like a wide rectangle. The tibia in most fossil sloths is proportionally short and is also massively constructed. As is true of the hand, some sloth groups reduced the number of toes with only three present in some megatheriids.
Mummified sloth skin preserved in the arid caves of Chile, Argentina, Arizona and Nevada provides excellent information on ground sloth skin and fur. Small bony ossicles were embedded in the skin of the mylodontids Mylodon, Glossotherium and Paramylodon, and probably also in Eremotherium, but are definitely not present in the mummified skin of Nothrotheriops. The fur itself was either yellowish or reddish brown.
Locomotion and posture
The configuration of the ground sloth foot and ankle indicates that most of these animals were plantigrade (that is, they placed the entire surface of the foot on the ground). However, it was argued as early as the 1840s that at least some ground sloths walked with a pedolateral foot posture: that is, with most of the weight supported by the outer margins of the feet. This bizarre configuration meant that the dorsal surface of the foot faced laterally.
The centre of gravity in the ground sloth body and the strength of their hindlimb bones, pelvis and vertebrae indicate that at least some forms could walk bipedally. Fossil trackways confirm this. Most sloths have hands and hand claws that appear well suited for the manipulation of foliage and the robust tail seen in most fossil sloths suggests that they may have sat in a tripodal posture when foraging and eating. The tripodal abilities of ground sloths have proved inspirational to palaeontologists working on other fossil tetrapod groups.
Living tree sloths are good swimmers so it seems reasonable to assume that ground sloths were too. However, a few fossil sloths reveal morphological features which indicate that they were habitual, rather than occasional, swimmers and amphibious habits have been suggested for both scelidotheriine mylodontids and nothrotheriids. One group of nothrotheriid seems to have been truly semi-aquatic (Muizon & McDonald 1995, Muizon et al. 2003, 2004).
For previous Tet Zoo articles on sloths and other xenarthrans, see...
- Ten things you didn't know about sloths (done in 2007, now in major need of an update)
- What was that skull? (on glyptodonts)
And - - seeing as this is another article on Cenozoic South American megafauna, I'm sure you're wondering how it's going with that montage I featured here back in July's toxodont article. Here's the answer... (still working on it: a larger version will be uploaded to my deviantART gallery later today)...
Refs - -
Sloth Body Parts
- ., Vizcaíno, S. F., Archuby, F. M. & Blanco, R. E. 2000. Limb bone proportions, strength and digging in some Lujanian (Late Pleistocene-Early Holocene) mylodontid ground sloths (Mammalia, Xenarthra). Journal of Vertebrate Paleontology 20, 601-610.
Cartelle, C. & De Iuliis, G. 1995. Eremotherium laurillardi: the Panamerican late Pleistocene megatheriid sloth. Journal of Vertebrate Paleontology 15, 830-841.
Gaudin, T. J. 1995. The ear region of edentates and the phylogeny of the Tardigrada (Mammalia, Xenarthra). Journal of Vertebrate Paleontology 15, 672-705.
- . 2004. Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): the craniodental evidence. Zoological Journal of the Linnean Society 140, 255-305.
Muizon, C. de & McDonald, H. G. 1995. An aquatic sloth from the Pliocene of Peru. Nature 375, 224-227.
A Sloths Digestive System Functions
Sloths look like some kind of slow-motion monkey and have long had a reputation for being lazy. The reason they move so slowly has a lot to do with what they eat: a variety of leaves, stems, buds, and some fruit. This kind of diet requires a special digestive system. Sloths have a large, four-chambered stomach, like a cow. Bacteria in their gut help digest the large amount of plant matter they eat. Due to the low nutritional value of their leafy diet, sloths usually move at a leisurely pace and sleep a great deal. They sleep 15 to 18 hours per day and (slowly) look for food at night. Even their innards move slowly, and some food items can take an entire month to digest! This slow metabolism helps sloths survive injuries that would kill other animals.
At the San Diego Zoo, our two-toed sloths eat low-starch, high-fiber biscuits, fresh fruits and veggies, and a variety of fresh browse.
SaveSave
Sloth romance:These ponderous animals spend most of their time alone. But when a female is ready to breed, she lets out a nighttime 'scream' that alerts any interested males. If more than one male reaches her at the same time, they slowly fight each other while hanging by their rear legs! Winner takes all, and several months later, the female gives birth (while upside down) to a single offspring.
The youngster must grab onto its mother's hair at birth and find its way to her nipples to nurse. The mother's body position looks like a comfortable hammock of sorts as baby rests on her chest. The baby begins sampling solid foods at about 10 days but still nurses for about a month. After that, the youngster continues to cling to its mother's belly but eats whatever she eats. It first hangs upside down on its own at 20 to 25 days.
The sloth youngster stays with its mother for six months to two years, depending on the subspecies. It then 'branches off' to live on its own. The young inherits a part of the home range left vacant by the mother, as well as her taste for certain leaves. Several sloths can live in a similar home range without competing for food or space.
A sloth's voice sounds like the hiss of a deflating balloon, but the animal can also squeal and grunt as needed. A low bleat signals distress—sloth ears are most tuned to low-frequency sounds. The sloth has an excellent sense of smell. Males scent mark on tree branches from a gland on the rump.
SaveSave
We exhibited two-toed sloths in our early years, but without much success. In the early 1930s, we managed to keep a mother and her baby alive for three years.
A Sloths Digestive System Homeostasis
Today, we have several Linné's two-toed sloths at the Zoo and the Safari Park, serving as animal ambassadors for their species. Xena, born at the Zoo in 2013, meets guests up close during special animal presentations—and occasionally she is joined by her new baby, born in April 2019. The baby's father is another animal ambassador—a handsome male sloth named Brad Pitt.
Though not uncommon in the wild, deforestation and other forms of habitat destruction remain threats for the sloth.Other human-made threats include power lines and roads. Educating children and adults in the sloths' home countries about the animals' importance to the ecosystem—and how to treat sloths respectfully—remains a challenge for those who want to help this unique and wonderful animal.
Both two-toed sloth species live in zoos. Yet identifying the two has always been problematic—they look alike! Based on the genetic information, a senior research associate in our Genetics Division designed a low-cost, easy-to-use genetic tool to identify two-toed sloths and improve management of the captive population. This tool allows visualizing DNA differences between species in a polymer matrix, a procedure that uses non-sophisticated tools in simple laboratory settings.
You can help us bring sloths and other species back from the brink by supporting the San Diego Zoo Global Wildlife Conservancy. Together we can save and protect wildlife around the globe.
Everybody loves sloths, and whenever we talk about sloths we have to remember that the two living kinds (Bradypus – the four species of three-toed sloth – and Choloepus – the two species of two-toed sloth) are but the tip of the iceberg when it comes to sloth diversity. This article – an excerpt from Naish (2005) (though with citations added that were absent in the published article) – briefly reviews the anatomy of fossil sloths, though there are references to the living forms where appropriate.
A typical fossil sloth can be imagined as a rather bear-shaped, shaggy-furred mammal with particularly powerful forelimbs, a barrel-shaped ribcage, a stout tail, prominent curved hand and foot claws and a markedly broad, robust pelvis.
Sloth skulls are diverse in form and range from the deep and broad, snub-faced morphology seen in Bradypus and some megalonychids to the elongate almost horse-like skulls of megatheriids and others (Gaudin 2004). Some megalonychids had a domed cranium resulting from marked enlargement of the sinuses within the frontal bones. The sloth palate is rugose and covered in pits and grooves and there are distinctive deep laminae that descend ventrally from the pterygoid bones (Gaudin 2004). The tip of the sloth mandible is usually spout-shaped and there is a foramen, representing an external opening of the mandibular canal, on the side of the lower jaw. In sloths with particularly long-rooted teeth there is a distinct bulge on the ventral margin of the lower jaw.
Sloths have peculiar teeth. They do not possess deciduous teeth but have a single set of high-crowned, open-rooted teeth (Bargo et al. 2006) that grow continuously throughout life, and the lack of a replacement dentition has made it difficult to homologise sloth teeth with those of other mammals. Incisors are absent, and it is not really possible to distinguish between the similar premolars and molars. The living tree sloth Choloepus, as well as some mylodontids, megalonychids and nothrotheriids, possess caniniform teeth separated from the other teeth by a diastema. The upper caniniforms of these sloths are ahead of the lower caniniforms and, while some evidence suggests that the upper caniniform in Choloepus is a true canine, this probably isn't the case for the lower caniniform. In the Pleistocene megalonychid Megalocnus from Cuba, and in certain other genera, the two most anterior upper jaw teeth have been described as ‘pseudorodentiform' and are more incisiform than caniniform.
Sloth teeth lack enamel and are composed instead of two different kinds of dentine plus an outer layer of cementum, the softer dentine forming the innermost region of the tooth. When sloth teeth erupt they are devoid of the cusps and basins seen normally in mammalian teeth and are simple and cylindrical in form. As the teeth occlude against those in the opposite jaw, valleys and cusp-like structures are formed as the two kinds of dentine erode differentially (Naples 1989, 1995). Some fossil sloths had squarish or subrectangular teeth and, in these forms, transverse ridges between the valleys are particularly prominent.
Arms, hands and hips
The forelimbs of most sloths are about subequal in length to the hindlimbs, the most prominent exceptions being the long-armed tree sloths of the genus Bradypus. Mylodontids had a particularly prominent olecranon process on the ulna. Recent studies have shown that the length of the olecranon process relative to the rest of the ulna is a good indicator of digging ability in mammals as the olecranon provides the attachment area for the triceps, the main muscle used in digging. Forelimb bone strength in mylodontids was also high and shows that the forelimbs were resistant to impact with the ground (Bargo et al. 2000). Furthermore, the wide, straight and relatively flat claws of these sloths resemble those of living mammals that dig. Accordingly, mylodontids seem to have been proficient diggers that unearthed roots and tubers and they may even have constructed burrows.
Sloths are amazingly diverse and unusual in hand morphology. Among megatheriids, primitive species of Eremotherium were pentadactyl (albeit it with a short thumb and a fifth digit with only one phalanx) while the advanced species E. laurillardi was tridactyl, possessing only digits III-V, and of these only digits III and IV had unguals (Cartelle & De Iuliis 1995).
Bradypus, a taxon that's notable for being outside the clade that includes the majority of other sloth lineages (Gaudin 2004, Pujos et al. 2007), possesses only digits II-IV on the hand, and the megalonychid Choloepus only has II and III. Several sloth groups exhibit fusion of various manual phalanges, including of both phalanges in the thumb (in Eremotherium) and of the two phalanges at the base of the third digit (in Thalassocnus), as well as fusion of metacarpals to carpals.
The sloth pelvis is massive and broad and unusual in that the ischia are connected to the vertebral column (in most tetrapods only the ilia are connected), a feature that sloths share with all other xenarthrans with the sole exception of Cyclopes, the Pygmy anteater. The femur in fossil sloths varies from robust to very robust with the femora of giant megatheriids being shaped like a wide rectangle. The tibia in most fossil sloths is proportionally short and is also massively constructed. As is true of the hand, some sloth groups reduced the number of toes with only three present in some megatheriids.
Mummified sloth skin preserved in the arid caves of Chile, Argentina, Arizona and Nevada provides excellent information on ground sloth skin and fur. Small bony ossicles were embedded in the skin of the mylodontids Mylodon, Glossotherium and Paramylodon, and probably also in Eremotherium, but are definitely not present in the mummified skin of Nothrotheriops. The fur itself was either yellowish or reddish brown.
Locomotion and posture
The configuration of the ground sloth foot and ankle indicates that most of these animals were plantigrade (that is, they placed the entire surface of the foot on the ground). However, it was argued as early as the 1840s that at least some ground sloths walked with a pedolateral foot posture: that is, with most of the weight supported by the outer margins of the feet. This bizarre configuration meant that the dorsal surface of the foot faced laterally.
The centre of gravity in the ground sloth body and the strength of their hindlimb bones, pelvis and vertebrae indicate that at least some forms could walk bipedally. Fossil trackways confirm this. Most sloths have hands and hand claws that appear well suited for the manipulation of foliage and the robust tail seen in most fossil sloths suggests that they may have sat in a tripodal posture when foraging and eating. The tripodal abilities of ground sloths have proved inspirational to palaeontologists working on other fossil tetrapod groups.
Living tree sloths are good swimmers so it seems reasonable to assume that ground sloths were too. However, a few fossil sloths reveal morphological features which indicate that they were habitual, rather than occasional, swimmers and amphibious habits have been suggested for both scelidotheriine mylodontids and nothrotheriids. One group of nothrotheriid seems to have been truly semi-aquatic (Muizon & McDonald 1995, Muizon et al. 2003, 2004).
For previous Tet Zoo articles on sloths and other xenarthrans, see...
- Ten things you didn't know about sloths (done in 2007, now in major need of an update)
- What was that skull? (on glyptodonts)
And - - seeing as this is another article on Cenozoic South American megafauna, I'm sure you're wondering how it's going with that montage I featured here back in July's toxodont article. Here's the answer... (still working on it: a larger version will be uploaded to my deviantART gallery later today)...
Refs - -
Sloth Body Parts
- ., Vizcaíno, S. F., Archuby, F. M. & Blanco, R. E. 2000. Limb bone proportions, strength and digging in some Lujanian (Late Pleistocene-Early Holocene) mylodontid ground sloths (Mammalia, Xenarthra). Journal of Vertebrate Paleontology 20, 601-610.
Cartelle, C. & De Iuliis, G. 1995. Eremotherium laurillardi: the Panamerican late Pleistocene megatheriid sloth. Journal of Vertebrate Paleontology 15, 830-841.
Gaudin, T. J. 1995. The ear region of edentates and the phylogeny of the Tardigrada (Mammalia, Xenarthra). Journal of Vertebrate Paleontology 15, 672-705.
- . 2004. Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): the craniodental evidence. Zoological Journal of the Linnean Society 140, 255-305.
Muizon, C. de & McDonald, H. G. 1995. An aquatic sloth from the Pliocene of Peru. Nature 375, 224-227.
A Sloths Digestive System Functions
- ., McDonald, H. G., Salas, R. & Urbina, M. 2003. A new early species of the aquatic sloth Thalassocnus (Mammalia, Xenarthra) from the Late Miocene of Peru. Journal of Vertebrate Paleontology 23, 886-894.
- ., McDonald, H. G., Salas, R. & Urbina, M. 2004. The youngest species of the aquatic sloth Thalassocnus and a reassessment of the relationships of the nothrothere sloths (Mammalia: Xenarthra). Journal of Vertebrate Paleontology 24, 387-397
Naish, D. 2005. Fossils explained 51: sloths. Geology Today 21 (6), 232-238.
Naples, V. L. 1989. The feeding mechanism in the Pleistocene ground sloth, Glossotherium. NaturalHistoryMuseum of Los AngelesCounty, Contributions in Science 415, 1-23.
Digestive System Steps
- . 1995. The artificial generation of wear patterns on tooth models as a means to infer mandibular movement during feeding in mammals. In Thomason, J. (ed) Functional Morphology in Vertebrate Paleontology. Cambridge University Press, pp. 136-150.
Pujos, F., de Iuliis, G., Argot, C. & Lars, W. 2007. A peculiar climbing Megalonychidae from the Pleistocene of Peru and its implication for sloth history. Zoological Journal of the Linnean Society 149, 179-235.
POSTSCRIPT: how could I write about sloths and not include this? ...
