What are the distinctive features of the external structure characteristic of mammals?

The mammalian head is relatively small and mobile due to the flexible and well-defined neck. There are mobile auricles on the head. Eyelashes are located on the eyelids that protect the eyes. The mouth of mammals has upper and lower lips, and their nose is elongated. The vast majority of mammals (except primates) move on four limbs located under the body. Due to this arrangement, the body is raised above the ground, which makes it possible to develop high speed when moving. The body surface of most mammals is hairy.