''Catonyx'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

ground sloth Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. They varied widely in size with the largest, belonging to genera '' Lestodon'', ''Eremotherium'' and ''Megatherium'', being around the size of elephants. ...

of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Scelidotheriidae Scelidotheriidae is a family of extinct ground sloths within the order Pilosa, suborder Folivora and superfamily Mylodontoidea, related to the other extinct mylodontoid family, Mylodontidae, as well as to the living two-toed sloth family Choloepo ...

, endemic to

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

during the Pliocene and

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

epochs. It lived from 2.5 Ma to about 10,000 years ago, existing for approximately . The most recent date obtained is about 9600 B.P.

Description

This animal, like many other terrestrial sloths, was of conspicuous size and mighty build. It had to reach and exceed 4 meters in length, and the skull alone was at least 50 centimeters long. Its weight has been estimated at over 1500 kg. The snout of ''Catonyx'' was elongated, although not as in some similar forms (e.g., '' Scelidotherium''). Unlike the latter, ''Catonyx'' possessed shorter premaxillae that formed a triangular (and not rectangular like '' Scelidotherium'') snout tip, a pronounced rostrum bulge, a palate equipped with a median groove, and larger teeth. In addition, the mandibular

symphysis A symphysis (, : symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together o ...

was elongated and elevated, and the posterior lobe of the lower fourth molar was more curved than that of ''Scelidotherium.'' Like all terrestrial sloths, ''Scelidotherium'' possessed strong-boned limbs and large

claws A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tars ...

Taxonomy

At a cave in Lagoa Santa,

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Peter Wilhelm Lund Peter Wilhelm Lund (14 June 1801 – 25 May 1880) was a Danish Brazilian paleontologist, zoologist, and archeology, archeologist. He spent most of his life working and living in Brazil. He is considered the father of Brazilian paleontology as wel ...

and his crew members collected the fragmentary fossils of a fossil sloth that Wilhelm named ''Megalonyx cuvieri'' in 1838. ''Catonyx,'' the genus name, was made by Ameghino in 1891. It was assigned to Scelidotheriinae by Gaudin in 1995. Scelidotheriinae was elevated back to family status by Presslee ''et al.'' in 2019. The very first fossils of this animal were found in Upper Pleistocene strata of

and were described by

Lund Lund (, ;"Lund"
(US) and ) is a city in the provinces of Sweden, province of Scania, southern Swed ...

in 1839, but for a long time there was considerable systematic confusion: the remains were gradually attributed to the genera '' Scelidotherium'' and '' Scelidodon''. Only recently have revisions based on clear morphological anatomy been proposed, according to which the genera ''Scelidotherium'' and ''Catonyx'' are two valid

taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

, while ''Scelidodon'' may or may not be a valid genus. ''Catonyx,'' in any case, is a member of the Scelidotheriidae, a group of terrestrial sloths known from the Miocene, Pliocene, and Pleistocene and characterized by an elongated snout; scelidotheres themselves part are usually placed as a subfamily of the

Mylodontidae Mylodontidae is a family of extinct South American and North American ground sloths within the suborder Folivora of order Pilosa, living from around 23 million years ago (Mya) to 11,000 years ago. This family is most closely related to another fa ...

, although they are sometimes considered a separate family,

. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

of ''Catonyx'' is '' Catonyx cuvieri'', named in 1839 by

. ''C. cuvieri'' has been found in Brazil and

Uruguay Uruguay, officially the Oriental Republic of Uruguay, is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast, while bordering the Río de la Plata to the south and the A ...

, and dates to the Late Pleistocene and likely the Early Holocene. Other species attributed to this genus but are sometimes considered to belong to a separate genus, ''Scelidodon'', are ''C. tarijensis'' and ''C. chiliense,'' found in

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

, Argentina, Uruguay, Bolivia, and Ecuador. Below is a phylogenetic tree of the Scelidotheriinae, based on the work of Nieto and colleagues (2020), showing the position of ''Catonyx''.

Palaeobiology

The cranial anatomy of the species ''C. tarijensis'' indicates it may have been a browser which used its strong lips to grab vegetation, and Santos Pereira et al. (2013) tentatively suggested browsing habits for ''C. cuvieri''. Isotopic analysis of ''

Smilodon ''Smilodon'' is an extinct genus of Felidae, felids. It is one of the best known saber-toothed predators and prehistoric mammals. Although commonly known as the saber-toothed tiger, it was not closely related to the tiger or other modern cats ...

populator'' remains from

indicates that ''Catonyx'' was one of its main prey items.

Fossil distribution

Fossils of ''Catonyx'' have been uncovered in

, the San José Formation of

, the Tezanos Pinto Formation of

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

, and the Tarija Valley of Bolivia.

Paleoecology

In the Brazilian Intertropical Region in eastern Brazil, ''Catonyx'' was a browser in arboreal savannahs and forested grasslands. Large, mesoherbivorous mammals in the BIR were widespread and diverse, including the cow-like toxodontids '' Toxodon platensis'' and '' Piauhytherium'', the macraucheniid litoptern ''

Xenorhinotherium ''Xenorhinotherium'' is an extinct genus of macraucheniine macraucheniids, native to northern South America during the Pleistocene and Holocene epoch, closely related to ''Macrauchenia'' of Patagonia. The type species is ''X. bahiense''.

'' and equids such as '' Hippidion principale'' and '' Equus neogaeus.'' Toxodontids were large mixed feeders as well and lived in forested areas, while the equids were nearly entirely grazers. Other xenarthran fossils are present in the area as well from several different families, like the giant megatheriid

Eremotherium ''Eremotherium'' (from Greek for "steppe" or "desert" "beast": ἔρημος "steppe or desert" and θηρίον "beast") is an extinct genus of giant ground sloth in the family Megatheriidae. ''Eremotherium'' lived in southern North America, Cen ...

,'' the fellow scelidotheriid '' Valgipes'', the mylodontids '' Glossotherium'', '' Ocnotherium'', and '' Mylodonopsis''. Smaller ground sloths such as the megalonychids '' Ahytherium'' and '' Australonyx'' and the nothrotheriid '' Nothrotherium'' have also been found in the area. ''Eremotherium'' was a generalist, while ''Nothrotherium'' was a specialist for trees in low density forests, and ''Valgipes'' was an intermediate of the two that lived in arboreal savannahs. Other glyptodonts and cingulates like the grazing glyptodonts '' Glyptotherium'' and '' Panochthus'' and the omnivorous pampatheres '' Pampatherium'' and '' Holmesina'' were present in the open grasslands. A

proboscidea Proboscidea (; , ) is a taxonomic order of afrotherian mammals containing one living family (Elephantidae) and several extinct families. First described by J. Illiger in 1811, it encompasses the elephants and their close relatives. Three l ...

n species has also been found in the BIR, '' Notiomastodon platensis,'' which was also present and was a mixed grazer on the open grasslands. Carnivores included some of the largest known mammalian land carnivores, like the giant felid '' Smilodon populator'' and the bear '' Arctotherium wingei.''Keeley, J. E., & Rundel, P. W. (2003). Evolution of CAM and C4 carbon-concentrating mechanisms. ''International journal of plant sciences'', ''164''(S3), S55-S77. Several extant taxa are also known from the BIR, like

guanaco The guanaco ( ; ''Lama guanicoe'') is a camelid native to South America, closely related to the llama. Guanacos are one of two wild South American camelids; the other species is the vicuña, which lives at higher elevations. Etymology The gua ...

giant anteater The giant anteater (''Myrmecophaga tridactyla'') is an Insectivore, insectivorous mammal native to Central America, Central and South America. It is the largest of the four living species of anteaters, which are classified with sloths in the or ...

s, collared peccaries, and striped hog-nosed skunks.Cartelle, Castor; Hartwig, W. C. (1996). "A new extinct primate among the Pleistocene megafauna of Bahia, Brazil". Proceedings of the National Academy of Sciences. 93 (13): 6405–6409. Two crab-eating types of extant mammals are also known from the BIR, the crab-eating raccoon and the crab-eating fox, indicating that crabs were also present in the region. The environment of the BIR is unclear, as there were both several species that were grazers, but the precede of the arboreal fossil monkeys '' Protopithecus'' and '' Caipora'' in the area causes confusion over the area's paleoenvironment. Most of

was thought to have been covered in open tropical

cerrado The Cerrado () is a vast ecoregion of Tropics, tropical savanna in central Brazil, being present in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Maranhão, Piauí, Bahia, Minas Gerais, São Paulo (state), São Paulo, Paraná ...

vegetation during the Late Pleistocene, but if ''Protopithecus'' and ''Caipora'' were arboreal, their presence suggests that the region may have supported a dense closed forest during the Late Pleistocene. It is possible that the region alternated between dry open savannah and closed wet forest throughout the climate change of the Late Pleistocene.Halenar, Lauren B. (December 2011). "Reconstructing the Locomotor Repertoire of Protopithecus brasiliensis". The Anatomical Record. 294 (12): 2048–2063.

Description

Taxonomy

Palaeobiology

Fossil distribution

Paleoecology

References

Further reading