This website uses cookies to ensure you get the best experience on our website. Learn more. Mammal diversity The first mammals evolved about million years ago. Mammal features All mammals including humans have the same distinctive features. These include: fur or hair growing from the skin mammary glands that, in females, produce milk for feeding the young three bones the malleus, incus and stapes in the middle ear for transmitting sound to the inner ear a single bone the dentary on each side of the lower jaw.
Close Modal Dialog. Stay in the know Uncover the secrets of the Australian Museum with our monthly emails. Sign up today. One of these is not a mammal. Which one? Characteristics of Mammals Two characteristics are used to define the mammal class. Female mammals have mammary glands. The glands produce milk after the birth of offspring. Milk is a nutritious fluid. It contains disease-fighting molecules as well as all the nutrients a baby mammal needs.
Producing milk for offspring is called lactation. Mammals have hair or fur. It insulates the body to help conserve body heat. It can also be used for sensing and communicating.
For example, cats use their whiskers to sense their surroundings. They also raise their fur to look larger and more threatening see Figure below. The skin of many mammals is covered with sweat glands. Mammals are known to have determinate growth, but so do birds, and at least the American alligator. Four-chambered hearts aren't exclusive to mammals either, as both birds and crocodilians have them too.
By using the site, you agree to the uses of cookies and other technology as outlined in our Policy, and to our Terms of Use. Mammary Glands Mammals got their name from this evolutionary adaptation. Hair Hair on mammals is an adaptation that provides insulation to keep the animal warm, provide protection to the animal's skin, provides camouflage through color patterns and helps the animal by providing greater sensory input through touch.
Middle Ear Bones All mammals have three middle ear bones, commonly called the hammer, anvil and stirrup. Sweat Glands Sweat glands, while being unique to mammals, aren't present in all mammals. Temperature Regulation While most mammals are warm-blooded, not all are able to regulate their temperature, which is the definition of being warm-blooded.
Other Characteristics Not Unique to Mammals Other characteristics not unique to mammals include live birth, determinate growth and a four-chambered heart. National Geographic: Platypus.
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