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.
[5]
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.[6] Scelidotheriinae was elevated back to family status by Presslee et al. in 2019.[7]
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 taxa, 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.[7]
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.[8] 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, 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.[9]
The cranial anatomy of the species C. tarijensis indicates it may have been a browser which used its strong lips to grab vegetation,[10] and Santos Pereira et al. (2013) tentatively suggested browsing habits for C. cuvieri.[11] Isotopic analysis of Smilodon populator remains from Brazil indicates that Catonyx was one of its main prey items.[12]
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 toxodontidsToxodon platensis and Piauhytherium, the macraucheniidlitopternXenorhinotherium 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 megatheriidground slothEremotherium, the fellow scelidotheriidValgipes, the mylodontidsGlossotherium, Ocnotherium, and Mylodonopsis. Smaller ground sloths such as the megalonychidsAhytherium and Australonyx and the nothrotheriidNothrotherium 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 pampatheresPampatherium and Holmesina were present in the open grasslands. A proboscidean 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.[14][15] Several extant taxa are also known from the BIR, like guanacos, giant anteaters, collared peccaries, and striped hog-nosed skunks.[16] 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.[16] 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.[16][17] It is possible that the region alternated between dry open savannah and closed wet forest throughout the climate change of the Late Pleistocene.[18]
^Fiedal, Stuart (2009). "Sudden Deaths: The Chronology of Terminal Pleistocene Megafaunal Extinction". In Haynes, Gary (ed.). American Megafaunal Extinctions at the End of the Pleistocene. Vertebrate Paleobiology and Paleoanthropology. Springer. pp. 21–37. doi:10.1007/978-1-4020-8793-6_2. ISBN978-1-4020-8792-9.
^dos Santos Pereira, I. C.; et al. (2013). "Record of the giant sloth Valgipes bucklandi (Lund, 1839) (Tardigrada, Scelidotheriinae) in Rio Grande do Norte state, Brazil, with notes on taphonomy and paleoecology". Journal of South American Earth Sciences. 43: 42–45. Bibcode:2013JSAES..43...42P. doi:10.1016/j.jsames.2012.11.004.
^Keeley, J. E., & Rundel, P. W. (2003). Evolution of CAM and C4 carbon-concentrating mechanisms. International journal of plant sciences, 164(S3), S55-S77.
^ abcCartelle, 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.
^Eisenberg, John F.; Redford, Kent H. (1989). Mammals of the Neotropics, Volume 3: Ecuador, Bolivia, Brazil. University of Chicago Press. p. 247. ISBN978-0-226-19542-1.
^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
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
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
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