This chapter reviews the paleobiology of pilosans (anteaters and sloths) from theSanta Cruz Formation, which comprise at least one genus of vermilinguan and 11genera of sloths. Paleobiological studies performed on these xenarthransinclude: estimation of body mass (through multivariate regression); analysis ofthe limbs so as to infer the locomotor habits and substrate use (throughmorphometric and qualitative-comparative morphofunctional analyses), and studiesof the masticatory apparatus to infer probable feeding habits (mainly throughanalysis of tooth morphology and wear facets, plus the anatomy of themasticatory apparatus as a whole). Santacrucian anteaters were small animals,about 6 kg, well suited for climbing and for scratch-digging the substrate insearching for their preferred food, social insects. Various sloths weremoderately large-sized forms, the largest reaching about 100 kg, with alocomotor pattern distinct from that of living sloths, resembling more that ofvermilinguans and pangolins. The results suggest well-developed diggingcapabilities, but semi-arboreal habits cannot be ruled out. Megatherioid slothswere most likely leaf eaters, and the primary method of food reduction must havebeen by shearing or cutting (with a predominance of orthal movements).Mylodontid masticatory movements included a larger transverse component, andfood reduction must have been by crushing and grinding, which suggests they fedon more compact, three-dimensional, and fibrous food items such as theunderground storage organs of plants. The semi-arboreal habits suggested foranteaters and, probably, sloths indicate they lived in forests or that forestedareas were present nearby. The specialized feeding habits of vermilinguans areindicative of subtropical and warm temperate environments because they wouldhave depended on a year-round availability of social insects.