A nail is a horn-like envelope covering the tips of the fingers and toes in humans, most non-human primates, and a few other mammals. Nails are similar to claws in other animals. Fingernails and toenails are made of a tough protective protein called keratin. This protein is also found in the hooves and horns of different animals. The mammalian nail, claw, and hoof are all examples of unguis [plural ungues]. The nail also reaches a temperature of 90 degrees F. (See image 4 of the scorpion.)