Armadillos are mammals, not reptiles. These unique creatures, recognized by their distinctive armor, belong to the class Mammalia. They share many fundamental characteristics with other mammals.
Armadillos: True Mammals
Armadillos possess several biological traits that classify them as mammals. Like all mammals, they give birth to live young and nurse them with milk from mammary glands. While some reptile species give live birth, they do not produce milk.
Armadillos also exhibit endothermy, regulating their own body temperature internally. Though their body temperature can be lower than many other placental mammals, they maintain a stable internal temperature. They also have sparse, wiry hair on their underbelly, which provides some insulation.
Armadillos possess a four-chambered heart, a common mammalian trait. Their skeletal structure, including specialized teeth, aligns with mammalian anatomy. They have simple, peg-shaped teeth lacking enamel, adapted for their insectivorous diet. Strong claws are used for digging, a primary behavior for foraging and creating burrows.
Defining Mammals Versus Reptiles
The classification of animals into mammals and reptiles relies on distinct biological characteristics. Mammals are endothermic, maintaining a constant internal body temperature through metabolic processes. They typically have bodies covered in hair or fur for insulation. Mammals also possess mammary glands to produce milk for their young and generally give birth to live offspring. Their circulatory system includes a four-chambered heart.
In contrast, reptiles are ectothermic, commonly referred to as cold-blooded, meaning their body temperature fluctuates with their external environment. Their skin is covered in scales, providing protection but offering less insulation than hair or fur. Most reptiles reproduce by laying eggs, though some species do give live birth. Reptiles lack mammary glands and do not produce milk to feed their young. The majority of reptiles have a three-chambered heart, which differs from the more efficient four-chambered heart found in mammals.
The Source of the Misconception
The common misconception that armadillos are reptiles often stems from their hard, segmented armor. This armor, known as a carapace, is made of bony plates called osteoderms, which are embedded in the skin and covered by a layer of keratin. While visually similar to the scales of reptiles, armadillo osteoderms are structurally different. Reptilian scales are epidermal folds, whereas armadillo osteoderms are dermal bone formations that develop within the skin.
Despite their reptilian-like exterior, this armor is a unique mammalian adaptation. The bony plates provide protection, and in some species, like the three-banded armadillo, allow them to roll into a ball when threatened. Other superficial similarities contributing to the confusion include their low-slung posture and burrowing habits, which can be mistaken for behaviors more typical of some reptiles. However, these traits are adaptations to their environment and lifestyle, not indicators of reptilian lineage.