Duck-billed platypus and echidna are egg-laying mammals.
Warm-blooded creatures that give birth to their offspring are known as mammals. They are the most common animal species found in practically all environments.
They have mammary glands, which aid in the production of milk to nourish their young.
Oil glands (sebaceous glands) and sweat glands are found on their skin (sudoriferous glands). The hair on animals' bodies helps them adapt to their surroundings.
They are heterodont, which means they have a variety of teeth.