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All mammals are warm blooded.

Mammals give birth to live young with the exception of duck billed platypus.

At some point in their lives they have hair, this hair may fall out as they grow older, this happens in animals such as dolphins.

Every mammal is a vertebrate.

All mammals have lungs to breathe air.

They have mammary glands (nipples) to feed milk to their young with the exception of duck billed platypus that secretes milk through its fur.

hope this helped.

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Mammals have three characteristics that no other group shares;

They have *true* hair.

True hair grows from special skin cells called follicles. Some other animals have hair like structures, true hair is a a rod of cells that are reinforced by the protein keratin.All mammals have hair on some part of the body at some time in their life. Hair takes the form of fur, whiskers, quills ( hedge hogs, porcupines) or even horns (rhinoceros).

They produce milk for feeding young from mammary glands.

Both male and females posses mammary glands but male production of milk is neglgible at the most. ( Nipples are not mammary glands, they are the delivery system for milk and are connected to the mammary glands by ducts [tubes]. Breasts are not mammary glands, they are fatty and connective tissue protecting the glands. Udders are not mammary glands but a container of them. The platypus and echidna have mammary gland but no nipples. they also lay eggs which is why live birth is not a unique characteristic of mammals.)

The third characteristic is internal and not obvious. There are three very small bones in the middle ear between the ear drum and inner ear.

The bones are commonly called hammer, anvil, and stirrup because of their shape. They transform sound to nerve carried signals. The hammer and anvil are derived from what are jaw bones in all other vertebrates. No other group has such an arrangement.

There are other characteristics of mammals, as listed in first answer, but they are also shared by other groups. Some groupings of shared characteristics can identify mammals but only mammals have the three characteristics listed after the asterisks.

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12y ago

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