Catonyx is an extinct genus of ground sloth of the family Scelidotheriidae, endemic to South America during the Pliocene and Pleistocene epochs.[ PaleoBiology Database: Catonyx, basic info] 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 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.
Taxonomy
At a cave in Lagoa Santa,
Brazil, Peter Wilhelm Lund 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 Brazil and were described by Lund 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 taxon, 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, although they are sometimes considered a separate family, Scelidotheriidae.
The type species of Catonyx is Catonyx cuvieri, named in 1839 by Peter Wilhelm Lund. C. cuvieri has been found in Brazil and Uruguay, and dates to the Late Pleistocene and likely the Early Holocene.
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 populator remains from
Brazil indicates that
Catonyx was one of its main prey items.
Fossil distribution
Fossils of
Catonyx have been uncovered in
Brazil, the San José Formation of
Uruguay, the Tezanos Pinto Formation of
Argentina,
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
Toxodontidae Toxodon and
Piauhytherium, the
Macraucheniidae Litopterna Xenorhinotherium and equids such as
Hippidion and
Amerhippus. 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
Megatheriidae ground sloth Eremotherium, the fellow
Scelidotheriidae Valgipes, the
Mylodontidae Glossotherium,
Ocnotherium, and
Mylodonopsis. Smaller ground sloths such as the
Megalonychidae Ahytherium and
Australonyx and the
Nothrotheriidae 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
Cingulata like the grazing glyptodonts
Glyptotherium and
Panochthus and the omnivorous
Pampatheriidae Pampatherium and
Holmesina were present in the open grasslands. A
species has also been found in the BIR,
Notiomastodon, 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 and the bear
Arctotherium.[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
,
,
Collared peccary, 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
Brazil was thought to have been covered in open tropical
cerrado 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.
[Eisenberg, John F.; Redford, Kent H. (1989). Mammals of the Neotropics, Volume 3: Ecuador, Bolivia, Brazil. University of Chicago Press. p. 247. .] 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.]
Further reading
-
M. A. T. Dantas and M. H. Zucon. 2007. Occurrence of Catonyx cuvieri (Lund, 1839) (Tardigrada, Scelidotheriinae) in Late Pleistocene–Holocene of Brazil. Revista Brasileira de Paleontologia 10(2):129-132
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M. A. T. Dantas, M. H. Zucon, and A. M. Ribeiro. 2005. Megafauna Pleistocênica da fazenda elefante, Gararu, Sergipe, Brasil. Geociências 24(3):277-287
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A. M. Ghilardi, M. A. Fernandes, and M. E. Bichuette. 2011. Megafauna from the Late Pleistocene-Holocene deposits of the Upper Ribeira karst area, southeast Brazil. Quaternary International 245(2):369-378
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R. P. Lopes and J. C. Pereira. 2010. Fossils of Scelidotheriinae Ameghino, 1904 (Xenarthra, Pilosa) in the Pleistocene deposits of Rio Grande do Sul, Brazil. Gaea: Journal of Geoscience 6(1):44-52
