What are the distinguishing features of a mammal compared to other classes of animals?

All classes of vertebrates have their own distinguishing features that we can use to identify if an animal is indeed a mammal or not. The main classes of vertebrates can be simpified into mammals, fish, amphibians and reptiles. The features that all or most mammals have in common are as follows:

Are endothermic. Also known as “warm-blooded,” endothermic animals regulate their own body temperate which allows them to live in almost every climate on Earth.

Have hair on their bodies.

Produce milk to feed their babies. This allows them to spend more time with their young and teach them important skills they need to survive on their own.

Give birth to their offspring whole and do not lay an egg.