| Catonyx | |
|---|---|
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| Replica of aCatonyx skull at theMuseo delle Scienze | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Pilosa |
| Family: | †Scelidotheriidae |
| Genus: | †Catonyx Ameghino, 1891 |
| Species | |
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Catonyx is an extinctgenus ofground sloth of thefamilyScelidotheriidae, endemic toSouth America during the Pliocene andPleistocene epochs.[1] It lived from 2.5 Ma to about 10,000 years ago, existing for approximately2.49 million years.[2] The most recent date obtained is about 9600 B.P.[3][4]
This animal, like many other terrestrialsloths, 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 ofCatonyx 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 likeScelidotherium) snout tip, a pronounced rostrum bulge, a palate equipped with a median groove, and larger teeth. In addition, the mandibularsymphysis was elongated and elevated, and the posterior lobe of the lower fourthmolar was more curved than that ofScelidotherium. Like all terrestrial sloths,Scelidotherium possessed strong-boned limbs and largeclaws.
At a cave inLagoa Santa,Brazil,Peter Wilhelm Lund and his crew members collected the fragmentary fossils of a fossil sloth that Wilhelm namedMegalonyx 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 Pressleeet al. in 2019.[7]
The very first fossils of this animal were found in Upper Pleistocene strata ofBrazil and were described byLund in 1839, but for a long time there was considerable systematic confusion: the remains were gradually attributed to the generaScelidotherium andScelidodon. Only recently have revisions based on clear morphological anatomy been proposed, according to which the generaScelidotherium andCatonyx are two validtaxa, whileScelidodon 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 theMylodontidae, although they are sometimes considered a separate family,Scelidotheriidae.[7]
Thetype species ofCatonyx isCatonyx cuvieri, named in 1839 byPeter Wilhelm Lund.C. cuvieri has been found in Brazil andUruguay, 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, areC. tarijensis andC. chiliense, found inChile, Argentina, Uruguay, Bolivia, and Ecuador.
Below is a phylogenetic tree of theScelidotheriinae, based on the work of Nieto and colleagues (2020), showing the position ofCatonyx.[9]
| Scelidotheriinae |
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The cranial anatomy of the speciesC. tarijensis indicates it may have been abrowser which used its strong lips to grab vegetation,[10] and Santos Pereira et al. (2013) tentatively suggested browsing habits forC. cuvieri.[11] Isotopic analysis ofSmilodon populator remains fromBrazil indicates thatCatonyx was one of its main prey items.[12]
Fossils ofCatonyx have been uncovered inBrazil, theSan José Formation ofUruguay, theTezanos Pinto Formation ofArgentina,[13] and theTarija Valley of Bolivia.[10]
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-liketoxodontidsToxodon platensis andPiauhytherium, themacraucheniidlitopternXenorhinotherium and equids such asHippidion principale andEquus 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 giantmegatheriidground slothEremotherium, the fellowscelidotheriidValgipes, themylodontidsGlossotherium,Ocnotherium, andMylodonopsis. Smaller ground sloths such as themegalonychidsAhytherium andAustralonyx and thenothrotheriidNothrotherium have also been found in the area.Eremotherium was a generalist, whileNothrotherium was a specialist for trees in low density forests, andValgipes was an intermediate of the two that lived in arboreal savannahs. Other glyptodonts andcingulates like the grazing glyptodontsGlyptotherium andPanochthus and the omnivorouspampatheresPampatherium andHolmesina were present in the open grasslands. Aproboscidean 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 felidSmilodon populator and the bearArctotherium wingei.[14][15] Several extant taxa are also known from the BIR, likeguanacos,giant anteaters,collared peccaries, andstriped hog-nosed skunks.[16] Two crab-eating types of extant mammals are also known from the BIR, thecrab-eating raccoon and thecrab-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 monkeysProtopithecus andCaipora in the area causes confusion over the area's paleoenvironment. Most ofBrazil was thought to have been covered in open tropicalcerrado vegetation during the Late Pleistocene, but ifProtopithecus andCaipora 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]
