* Warm-blooded: Lions maintain a constant internal body temperature, regardless of the external environment.
* Hair or Fur: Lions have a distinctive mane of fur on the males, and a coat of fur covering their bodies.
* Give birth to live young: Lions don't lay eggs. They give birth to live cubs.
* Mammary glands: Female lions have mammary glands which produce milk to nourish their young.
* Three middle ear bones: Lions, like all mammals, have three bones in their middle ear (malleus, incus, stapes) which help with hearing.
* Four-chambered heart: Lions have a four-chambered heart, which is more efficient at circulating oxygenated blood than a three-chambered heart.
* Diaphragm: Lions have a diaphragm, a muscle that aids in breathing.
* Other mammalian traits: Lions also share other traits with other mammals, such as having a neocortex in their brain, producing sweat glands, and possessing a specialized jaw for chewing.
These features are shared by all mammals, and help to define them as a distinct class of animal.