Two-toed sloths

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Two-toed sloths
Hoffmann's two-toed sloth (Choloepus hoffmanni)

Hoffmann's two-toed sloth ( Choloepus hoffmanni )

Systematics
Superordinate : Sub-articulated animals (Xenarthra)
Order : Tooth arms (pilosa)
Subordination : Sloths (folivora)
Superfamily : Mylodontoidea
Family : Choloepodidae
Genre : Two-toed sloths
Scientific name of the  family
Choloepodidae
JE Gray , 1871
Scientific name of the  genus
Choloepus
Illiger , 1811

The two-toed sloths ( Choloepus ) are a genus of mammals from the family Choloepodidae and the suborder of the sloths . The term two-toed sloth, which is sometimes used for the group, is misleading in that they only have two toes on their front feet and three toes on their hind feet. The genus includes two recent species, the two- toed sloth ( Choloepus didactylus ) and the Hoffmann two-toed sloth ( Choloepus hoffmanni ). Both species inhabit the central and northern part of South America , the former is also found in parts of Central America . The two-toed sloths are mainly found in the tropical rainforests of the lowlands and mountains. They mostly feed on vegetable, occasionally also animal food. The animals live solitary and are nocturnal. Special features are above all the way of life and locomotion hanging with the back down in the branches, as well as the low metabolic rate , associated with very slow movements, due to the low-energy diet .

description

Habitus

Actual two- toed sloth ( Choloepus didactylus )

The two-toed sloths reach a head-torso length of 54 to 72 cm and a body weight of 3.3 to 9 kg. The body is perfectly adapted to a way of life that depends on the branches. In contrast to most other mammals, the fur of the animals is parted from the belly to the back to enable better drainage of rainwater. Its color varies from yellowish to gray-brown, with the head being lighter in color than the rest of the body, and the limbs sometimes darker. However, it can take on a green hue from algae. The head is rounded and has two small, forward-facing eyes with small pupils. The ears, which are also small, remain hidden in the fur, as does the short tail. In contrast to the three-toed sloth, the limbs are approximately the same length, with two toes on the front feet and three toes on the hind feet, all of which have long claws. However, the toe rays lying on the outside and inside are still rudimentary.

Skull and dentition features

Skull and lower jaw of a two-toed sloth

The skull of the two-toed sloth is short with an average of 10.9 cm, but longer than that of the three-toed sloth. It has a clearly rounded shape in profile. Characteristic features of sloths in general are the elongated upper jaw and the greatly shortened middle jawbone , which is also not in contact with the nasal bone . Furthermore, the zygomatic arch is not completely formed. On cheekbone two bony outgrowths put on. In the two-toed sloths, that of the zygomatic arch does not extend as clearly upwards as in the three-toed sloths, but rather is oriented backwards. It also almost touches the front end of the arch base of the temporal bone . The second bony outgrowth points diagonally backwards and downwards and is relatively and absolutely shorter than that of the three-toed sloth. Another difference can be found in the ear region: here the two-toed sloths, like almost all extinct ground-dwelling sloths, have formed a tympanic ring , in contrast to their more recent relatives with a tympanic bladder .

The spatulate, strongly ossified symphysis is typical of the lower jaw of the two-toed sloth . The articulated branches are relatively low compared to the three-toed sloth, so the articulation to the skull is only slightly above the chewing surface, which is reminiscent of predators . The dentition is distinguished from the other higher mammals by the lack of tooth enamel , and it is structured differently. The incisors and canines are generally missing . Each half of the jaw are formed in the maxilla and five in the mandible four teeth, for a total of 18. The rear have a molarenartige shape that is respective foremost eckzahnartig ( caniniform enlarged) designed and clearly, he that the other teeth surmounted. It is separated from the rest of the teeth by a gap ( diastema ). Most likely, the caniniform anterior tooth does not correspond to the actual canine tooth of the mammals, since the lower one lies behind the upper one when the dentition is closed and not - as usual - the other way around. The design of the teeth is believed to have originated in the sloth and also occurs in numerous fossil forms, such as the Mylodontidae . In contrast to the three-toed sloths, the opposing molars have an alternating position when the jaw closes.

Skeletal features

Skeleton of a two-toed sloth

With 5 to 7 cervical vertebrae, the neck is significantly shorter than that of the three-toed sloth (8 or 10). It is sometimes assumed that the first two rib-bearing thoracic vertebrae represent cervical vertebrae displaced back. The thoracic spine consists of 24 vertebrae, 21 of which serve as attachment points for ribs. Three-toed sloths, on the other hand, have only 16 thoracic vertebrae, 14 of which have ribs. The tail is extremely short and consists of only 4 to 5 vertebrae. The way of life hanging in the branches also led to changes in the musculoskeletal system, which differs somewhat from that of mammals living on the ground. The chest and shoulder areas are primarily affected, and this also includes changes in the arrangement of the muscles, for example in the area of ​​the chest and upper back muscles. These changes were necessary, on the one hand, to counteract the gravitation in the hanging way of life and, on the other hand, to ensure the drive to move, since here the front legs serve as a drive in contrast to ground-dwelling mammals.

hide

The fur of the two-toed sloth consists of only one layer, the outer hair , which is shaggy and long, with the hair in the shoulder area reaching up to 17 cm in length. The structure of the fur is different from that of the three-toed sloth with its two-layered coat. The shape of the hair also differs significantly from that of its three-fingered relatives. The diameter is only 0.16 mm, and 3 to 9 longitudinal ribs and grooves run along the entire length of the outer surface, which is unique among mammals. The cuticle is not continuous, but is interrupted by small dimples. Algae nest in the dimples , causing the fur to shimmer green in parts, which is particularly evident in the rainy season and increases the camouflage effect in the branches. The most common algae forms include red algae of the genus Rufusia and green algae such as Dictyococcus and Chlorococcum . As is common to all sloths, the hair lacks the medulla.

Utterances and sensory performances

Only a few vocalizations of the two-toed sloth are known; often it is calls from young animals that have been separated from the mother animal. Due to the structure of the ears, the animals can only perceive sounds in a low frequency range between 0.3 and 30 kHz, optimally between 0.5 and 3 kHz. As a result, adult animals are mainly activated by sounds of 2 to 8 kHz, which the young animals also take advantage of in search of the mother animal. The sense of sight is underdeveloped because the ciliary muscle is missing. This makes the animals myopic . The strongly curved cornea of the eye lens causes visual acuity of 3 to 4 diopters . However, the eyesight of the young is usually better than that of the adults.

distribution

The two-toed sloths live in Central and South America , their range extends from Nicaragua to Peru and Brazil . They inhabit tropical rainforests of the lowlands and mountains, but also partially deciduous forests and secondary forests. Occasionally, animals are observed in more open landscapes. Because of their single-layer fur, the two-toed sloths do not tolerate cooler temperatures. The thermal neutrality is around 24 ° C, which is higher than that of the three-toed sloth with its thick undercoat. For this reason, the two-toed sloths are rarely found in high mountain areas. However, one animal was spotted at an altitude of almost 3,300 m. Representatives of populations in higher-lying areas of distribution often have a denser coat.

Way of life

Social behavior and activities

Actual two-toed sloth in the branches

The way of life of wild two-toed sloths has not been adequately researched. They spend almost their entire life hanging in the branches, their way of life is geared towards saving energy due to the low nutritional value of their food. However, compared to the three-toed sloths, they are less picky about their food, which is why they are considered more "agile" than their relatives. Sleep, ingestion of food, mating and childbirth also take place in the hanging way of life; the two-toed sloths only leave the branches to get to another tree or to defecate. In the trees they can cover up to 40 m a day, in exceptional cases up to 300 m and more. The speeds achieved are 0.1 to 0.16 m per second (360 to 580 m per hour), maximum speeds were registered as 0.47 m per second (1690 m per hour). On the ground they are rather helpless and can only lift their bodies off the ground for a short time. However, they can swim very well. The animals sleep around 13 hours a day, their periods of activity are concentrated in the night. They are predominantly loners, individual animals use activity areas of 0.4 to 3.9 hectares in size. In more open landscapes, these can also be significantly larger. Territorial behavior could only rarely be observed. The population density varies depending on the region, between 0.04 and 2.7 individuals per hectare.

Diet and Metabolism

The two-toed sloths are less picky than the three-toed sloths; in addition to leaves , they also eat fruits , flowers and buds . Occasionally they also consume insects , bird eggs, and nestlings . The generally low-energy vegetable diet leads to a low metabolic rate , which is only 40 to 45% of a similarly large mammal and results in a very energy-saving lifestyle. Among other things, muscle contraction is 4 to 6 times slower than in a house cat , muscle relaxation is even 9 to 11 times slower. Defecation is usually only done once a week. The body temperature is variable and fluctuates between 32.7 and 35.5 ° C, especially during sleep or during cooler times of the day or in damp weather it sometimes drops sharply. Wild two-toed sloths sleep and rest for about 13 hours a day, with periods of increased, mostly nocturnal activity between the individual rest phases, which can last up to 7.5 hours. However, in order to obtain important supplements that are not available due to the rather low-energy food, a special symbiosis has developed in both the two-toed sloths and the three-toed sloths . Moths of the genus Cryptoses live in the fur and lay their eggs in the sloth's dung . They also give off nitrogen compounds to the algae that also live in the fur. By licking the fur, the two-toed sloths ingest the algae and thereby receive the supplements. The effect is more clearly developed in the three-toed sloth.

Reproduction

The mating is all year round, but with some populations it may also be dependent on the seasons and then takes place at the beginning of the dry season. The gestation period lasts ten to eleven months, and a single young is usually born. This is around 21 to 25 cm long and weighs around 360 to 450 g. It spends the first few weeks of life clinging to the mother's stomach, and when it is five weeks at the latest, it starts eating solid food. The lactation period is around five months. It becomes finally independent after six to nine months, but the process can also take up to two years. Females become sexually mature at around three years of age, males at four to five years. The interval between two births is about a year and a half. The life expectancy of the two-toed sloth in the wild is unknown; in human care, they can live to be 40 years and older. The highest documented age was a two-toed sloth that was at least 50 years old and kept in human care.

Predators and survival strategies

The most important predators are birds of prey such as the harpy , larger and smaller cats such as the jaguar and the ocelot and giant snakes such as anacondas . The two-toed sloths can defend themselves against predators with their front claws and teeth, but mostly they are camouflaged by their fur and their very slow movements.

Systematics

Internal systematics of the sloths according to Presslee et al. 2019 (based on protein analysis)
 Folivora  
  Megalocnoidea  

 Acratocnidae (†) 


   

 Parocnidae (†) 



   
  Megatherioidea  


 Nothrotheriidae (†) 


   

 Megatheriidae (†) 



   

 Megalonychidae (†) 


   

 Bradypodidae




  Mylodontoidea  

 Scelidotheriidae (†) 


   

 Choloepodidae


   

 Mylodontidae (†) 






Template: Klade / Maintenance / Style

The megalocnoid is subdivided according to Delsuc et al. 2019

Internal systematics of the sloths according to Varela et al. 2019 (based on skeletal anatomical features)
 Folivora  
  Eufolivora  
  Megatherioidea  


 Megatheriidae (†)


   

 Nothrotheriidae (†)



   

 Megalonychidae (including two-toed sloths )



 Mylodontoidea  


 Mylodontidae (†)


   

 Orophodontidae (†)



   

 Scelidotheriidae (†)




   

 Bradypodidae



Template: Klade / Maintenance / Style

The two-toed sloths ( Cholöoepus ) are a genus within the monotypic family of the Choloepodidae from the suborder of the sloths (Folivora). The sloths together with the anteaters (Vermilingua) form a closer family group, the tooth arms (Pilosa). These represent an order within the superordinate order of the secondary articulated animals (Xenarthra), which in turn belongs to one of the four main lines of the higher mammals . With the help of molecular genetic studies, a split of the sloths from the common line with the anteaters in the end of the Paleocene could be determined about 58 million years ago. The closest related group within the sloth today are the three-toed sloths ( Bradypus ) from the also monotypical family of the Bradypodidae.

The two- and three-toed sloths were originally thought to be closely related and both were relegated to the Bradypodidae family, which contrasted with the extinct ground-dwelling sloths. However, the external similarities are largely based on convergent evolution, as later skeletal-anatomical studies showed. In the period that followed, many scientists favored a closer relationship between the two-toed sloths and the ground-dwelling sloths from the Megalonychidae family, which was supported by the enlarged and canine-like front tooth, the structure of the zygomatic bone and the lack of an ossified tympanic membrane on the middle ear . For the three-toed sloths, however, a sister group relationship to all other sloths was assumed. With the advent of molecular genetic analysis methods, the time gap that clearly separates the two- and three-toed sloths from a phylogenetic point of view became apparent, as both genera had developed their own lines of development since the Oligocene around 29 million years ago.

Historical illustration of a two-toed sloth from 1902

In the classical view, the Megalonychidae were considered to be a very diverse group, made up of large ground sloths from South and North America as well as representatives of the West Indies . The two-toed sloths should be more closely related to the latter, including Neocnus and Acratocnus . The relationships between the two-toed sloths and the Megalonychidae remained largely unclear, as the heavily modified anatomy of today's tree sloths, which developed from their special way of life, made comparisons difficult. In addition, there are no fossil records of the two-toed sloths, which means that transitional forms are unknown. Extensive molecular genetic investigations and protein analyzes on the recent and fossil sloths from 2019 contradicted the common opinion of the relationships between the recent tree sloths on the one hand and the Megalonychidae in general on the other. The latter were found to be polyphyletic consisting of three lineages: the two-toed sloths, the large ground sloths of the continental American mainland, and the smaller sloths of the West Indies. For the two-toed sloth there is a closer relationship to the extinct Mylodontidae and Scelidotheriidae , which together form the superfamily of the Mylodontoidea . The ground sloths of North and South America are grouped with the Megatheriidae and the Nothrotheriidae , a relationship that was previously assumed and is united in the superfamily of the Megatherioidea . The three-toed sloths can also be found here. The Caribbean sloths in turn form an independent superfamily, the Megalocnoidea .

The two-toed sloths are divided into two recent species:

  • Actual two- toed sloth or unau ( Choloepus didactylus ( Linnaeus , 1758))
  • Hoffmann's two-toed sloth ( Choloepus hoffmanni Peters , 1858)

According to the available genetic studies, the two lines emerged in the Upper Miocene about 9 million years ago. A study from 2018 showed that these are not completely separated in the north-western Amazon basin. Whether this is due to hybridization , to a non-differentiable phenotype within the two-toed sloth or to insufficient information on the distribution of the two species cannot be said at the moment due to the lack of data. Hybrid forms occasionally occur in human captivity.

The first description of the genus Choloepus was made in 1811 by Johann Karl Wilhelm Illiger , where he the type species, the essential two-toed sloth, as Bradypus didactylus spoke, a name that Linnaeus had already used 1758th This was not changed until 1827 by John Edward Gray , who incorrectly used the name Chaelopus . According to Linnaeus, the type locality of the actual two- toed sloth was in Zeylona (today's Sri Lanka ), only in 1911 was Suriname established as the actual type locality by Oldfield Thomas . The generic name Choloepus comes from the Greek language and is derived from χωλός ( cholos “lame”) and πούς ( poús “foot”), thus referring to the slow movements of animals. The name Choloepus as the basis for naming a higher taxonomic unit was first used by John Edward Gray in 1871. He defined the tribe of the Choloepodini (as "Choloepina") and thus formally separated the two- and three-toed sloths at the tribe level. A correct spelling today goes back to Theodore Gill , who led the Choloepodinae as a subfamily in 1872.

threat

As inhabitants of the rainforests, two-toed sloths suffer from deforestation and the associated loss of their habitat. Another part of the threat is hunting, partly for food purposes, but also for sale as pets. Due to the wide distribution area, according to the IUCN , both species are considered "not endangered" ("least concern"). Unlike three-toed sloths, two-toed sloths are more often kept in zoos.

literature

  • Nadia Moraes-Barros: Megalonychidae (Two-toed sloths). In: Don E. Wilson, Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 8: Insectivores, Sloths and Colugos. Lynx Edicions, Barcelona 2018, pp. 104–117 ISBN 978-84-16728-08-4 .
  • Ronald Nowak: Walker's Mammals of the World. Johns Hopkins University Press, Baltimore 1999, ISBN 0-8018-5789-9 .

Individual evidence

  1. ↑ a b c d e f g h i Virginia Hayssen: Choloepus hoffmanni (Pilosa: Megalonychidae). In: Mammalian Species. 43 (1), 2011, pp. 37-55.
  2. ^ A b Peter J. Adam: Choloepus didactyla. In: Mammalian Species. 621, 1999, pp. 1-8.
  3. ^ A b c d Alfred L. Gardner, Virginia L. Naples: Family Megalonychidae P. Gervais, 1855. In: Alfred L. Gardner (Ed.): Mammals of South America. Volume 1: Marsupials, Xenarthrans, Shrews, and Bats. University of Chicago Press, 2008, ISBN 978-0-226-28240-4 , pp. 165-168.
  4. ↑ a b c d e f Nadia Moraes-Barros: Megalonychidae (Two-toed sloths). In: Don E. Wilson, Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 8: Insectivores, Sloths and Colugos. Lynx Edicions, Barcelona 2018, pp. 104–117 ISBN 978-84-16728-08-4 .
  5. ^ A b c Virginia L. Naples: Cranial osteology and function in the tree sloths. Bradypus and Choloepus. In: American Museum Novitates. 2739, 1982, pp. 1-21.
  6. ↑ Sergio F. Vizcaíno: The teeth of the “toothless”: novelties and key innovations in the evolution of xenarthrans (Mammalia, Xenarthra). In: Paleobiology. 35 (3), 2009, pp. 343-366.
  7. Jump up ↑ Lionel Hautier, Vera Weisbecker, Marcelo R. Sánchez-Villagra, Anjali Goswami, Robert J. Asher: Skeletal development in sloths and the evolution of mammalian vertebral patterning. In: PNAS. 107 (44), 2010, pp. 18903-18908 ( pnas.org ).
  8. ↑ Hideki Endo, Osamu Hashimoto, Hajime Taru, Keisuke Sugimura, Shin-ichi Fujiwara, Takuya Itou, Hiroshi Koie, Masato Kitagawa, Takeo Sakai: Comparative Morphological Examinations of the Cervical and Thoracic Vertebrae and Related Spinal Nerves in the Two-Toed Sloth. In: Mammal Study. 38 (3), 2013, pp. 217-224.
  9. ↑ John A. Nyakatura, Martin S. Fischer: Functional morphology of the muscular sling at the pectoral girdle in tree sloths: convergent morphological solutions to new functional demands? In: Journal of Anatomy. 219, 2011, pp. 360-374.
  10. ↑ a b c D. P. Gilmore, CP Da Costa, DPF Duarte: Sloth biology: an update on their physiological ecology, behavior and role as vectors of arthropods and arboviruses. In: Brazilian Journal of Medical and Biological Research. 34 (1), 2001, pp. 9-25 ( scielo.br ).
  11. ↑ a b c d Desmond Gilmore, Denia Fittipaldi Duarte, Carlos Peres da Costa: The physiology of two- and three-toed sloth. In: Sergio F. Vizcaíno, WJ Loughry (Ed.): The Biology of the Xenarthra. University Press of Florida, 2008, pp. 130-142.
  12. ↑ a b Mariella Superina, Tinka Plese, Nadia Moraes-Barros, Agustín Manuel Abba: The 2010 Sloth Red List Assessment. In: Edentata. 11 (2), 2010, pp. 115-134.
  13. ^ A b John A. Nyakatura, Alexander Petrovitch, Martin S. Fischer: Limb kinematics during locomotion in the two-toed sloth (Choloepus didactylus, Xenarthra) and its implications for the evolution of the sloth locomotor apparatus. In: Zoology. 113, 2010, pp. 221-234.
  14. ^ M. Zachariah Peery, Jonathan N. Pauli: The mating system of a 'lazy' mammal, Hoffmann's two-toed sloth. In: Animal Behavior. 84, 2012, pp. 555-562.
  15. ^ Adriano Garcia Chiarello: Sloth ecology. An overview of field studies. In: Sergio F. Vizcaíno, WJ Loughry (Ed.): The Biology of the Xenarthra. University Press of Florida, 2008, pp. 269-280.
  16. ↑ Jonathan N. Pauli, Jorge E. Mendoza, Shawn A. Steffan, Cayelan C. Carey, Paul J. Weimer, M. Zachariah Peery: A syndrome of mutualism reinforces the lifestyle of a sloth. In: Proceedings of the Royal Society. B 281, 2014, p. 20133006, doi: 10.1098 / rspb.2013.3006 .
  17. ↑ Erica Taube, Joël Keravec, Jean-Christophe Vié, Jean-Marc Duplantier: Reproductive biology and postnatal development in sloths, Bradypus and Choloepus: review with original data from the field (French Guiana) and from captivity. In: Mammal Review. 31 (3), 2001, pp. 173-188.
  18. ↑ DER SPIEGEL: Mourning the world's oldest sloth Paula: The end of comfort. ( online ), accessed on August 10, 2020.
  19. ↑ a b Samantha Presslee, Graham J. Slater, François Pujos, Analía M. Forasiepi, Roman Fischer, Kelly Molloy, Meaghan Mackie, Jesper V. Olsen, Alejandro Kramarz, Matías Taglioretti, Fernando Scaglia, Maximiliano Lezcano, José Luis Lanata, John Southon, Robert Feranec, Jonathan Bloch, Adam Hajduk, Fabiana M. Martin, Rodolfo Salas Gismondi, Marcelo Reguero, Christian de Muizon, Alex Greenwood, Brian T. Chait, Kirsty Penkman, Matthew Collins, Ross DE MacPhee: Palaeoproteomics resolves sloth relationships. In: Nature Ecology & Evolution. 3, 2019, pp. 1121-1130, doi: 10.1038 / s41559-019-0909-z .
  20. ↑ a b Frédéric Delsuc, Melanie Kuch, Gillian C. Gibb, Emil Karpinski, Dirk Hackenberger, Paul Szpak, Jorge G. Martínez, Jim I. Mead, H. Gregory McDonald, Ross DE MacPhee, Guillaume Billet, Lionel Hautier, Hendrik N Poinar: Ancient mitogenomes reveal the evolutionary history and biogeography of sloths. In: Current Biology. 29 (12), 2019, pp. 2031-2042, doi: 10.1016 / j.cub.2019.05.043 .
  21. ↑ a b Luciano Varela, P. Sebastián Tambusso, H. Gregory McDonald and Richard A. Fariña: Phylogeny, Macroevolutionary Trends and Historical Biogeography of Sloths: Insights From a Bayesian Morphological Clock Analysis. In: Systematic Biology. 68 (2), 2019, pp. 204-218.
  22. ↑ a b Frédéric Delsuc, Sergio F Vizcaíno, Emmanuel JP Douzery: Influence of Tertiary paleoenvironmental changes on the diversification of South American mammals: a relaxed molecular clock study within xenarthrans. In: BMC Evolutionary Biology. 4 (11), 2004, pp. 1-13.
  23. ↑ a b c Gillian C. Gibb, Fabien L. Condamine, Melanie Kuch, Jacob Enk, Nadia Moraes-Barros, Mariella Superina, Hendrik N. Poinar, Frédéric Delsuc: Shotgun Mitogenomics Provides a Reference Phylogenetic Framework and Timescale for Living Xenarthrans. In: Molecular Biology and Evolution. 33 (3), 2015, pp. 621–642.
  24. ^ George Gaylord Simpson: The Principles of Classification and a Classification of Mammals. In: Bulletin of the American Museum of Natural History. 85, 1945, pp. 1-350 (p. 72).
  25. ↑ a b Timothy J. Gaudin: Phylogenetic relationships among sloths (Mammalia, Xenarthra, Tardigrada): the craniodental evidence. In: Zoological Journal of the Linnean Society. 140, 2004, pp. 255-305.
  26. ↑ Timothy J. Gaudin: On the Osteology of the Auditory Region and Orbital Wall in the Extinct West Indian Sloth Genus Neocnus Arredondo, 1961 (Placentalia, Xenarthra, Megalonychidae). In: Annals of Carnegie Museum. 80 (1), 2011, pp. 5-28.
  27. ↑ a b Manuel Ruiz-García, Diego Chacón, Tinka Plese, Ingrid Schuler, Joseph Mark Shostell: Mitogenomics phylogenetic relationships of the current sloth's genera and species (Bradypodidae and Megalonychidae). In: Mitochondrial DNA Part A. 29 (2), 2018, pp. 281-299, doi: 10.1080 / 24701394.2016.1275602 .
  28. ↑ Cynthia C. Steiner, Marlys L. Houck, Oliver A. Ryder: Species identification and chromosome variation of captive two-toed sloths. In: Zoo Biology. 30 (6), 2011, pp. 623-635, doi: 10.1002 / zoo.20360 .
  29. ↑ Oldfield Thomas: The mammals of the tenth edition of Linnaeus; an attempt to fix the types of the genera and the exact bases and localities of the species. In: Proceedings of the Zoological Society of London. 1911, pp. 120-158.
  30. ^ John Edward Gray: Notes on the species of Bradypodidae in the British Museum. In: Proceedings of the Zoological Society of London. , 1871, pp. 428-449 ( online ).
  31. ^ Theodore Gill: Arrangement of the Families of Mammals. Washington 1872, pp. 1-98 (p. 24) ( online ).

Web links

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