Collier's New Encyclopedia (1921)/Ai

AI, a species of sloth, the bradypus tridactylus of Linnæus. As its name implies it has three toes, or rather nails, on each foot, in this respect differing from the unau (bradypus didactylus of Linnæus), which has but two. It is of the order edentata, or toothless mammals. It is the only known species of its class which has as many as nine cervical vertebræ, seven being the normal number. It is about the size of a cat. The tail is very short. The limbs also are short, but exceedingly muscular. It clings with extraordinary tenacity to the branches of trees. It inhabits America, from Brazil to Mexico.