Editing Xenarthra (section)

===Metabolism===
Living xenarthrans have the lowest metabolic rates among [[theria]]ns.<ref name="Basal Metabolic Rates in Mammals: A"/><ref>{{cite journal |first1=Barry G. |last1=Lovegrove |year=2000 |title=The Zoogeography of Mammalian Basal Metabolic Rate |journal=The American Naturalist |volume=156 |issue=2 |pages=201–219 |doi=10.1086/303383 |pmid=10856202 |jstor=3079219|s2cid=4436119 }}</ref> Paleoburrows have been discovered which are up to {{Convert|1.5|m|ft|0|abbr=on}} wide and {{Convert|40|m|abbr=on}} long, with claw marks from excavation referred to the ground sloths ''Glossotherium'' or ''Scelidotherium''. Remains of ground sloths (''Mylodon'' and others) in caves are particularly common in colder parts of their range, suggesting ground sloths may have used burrows and caves to help regulate their body temperature. Analysis of the fossil South American [[Luján River|Lujan]] fauna suggests far more large herbivorous mammals were present than similar contemporary environments can support. As most large Lujan herbivores were xenarthrans, low metabolic rate may be a feature of the entire clade, allowing relatively low-resource scrublands to support large numbers of huge animals. Faunal analysis also shows far fewer large predators in pre-[[Great American Interchange|GABI]] South American faunas than would be expected based on current faunas in similar environments. This suggests other factors than predation controlled the numbers of xenarthrans. South America had no placental predatory mammals until the Pleistocene, and xenarthran large-mammal faunas may have been vulnerable to many factors including a rise in numbers of mammalian predators, resource use by spreading North American herbivores with faster metabolisms and higher food requirements, and climate change.<ref name=":1" />