Pangolin is the only mammal wholly covered in scales

Pangolin.
Though many think of them as reptiles, pangolins are actually mammals. They are the only mammals wholly-covered in scales and they use those scales to protect themselves from predators in the wild. If under threat, a pangolin will immediately curl into a tight ball and will use their sharp-scaled tails to defend themselves.Pangolins eat ants, termites and larvae and are often known as "the scaly anteater." Because they have no teeth, pangolins pick up food with their sticky tongues, which can sometimes reach lengths greater than the animal’s body.

National Geographic