It has been theorized that this unique mammalian nose evolved from the anterior part of the upper jaw of the reptilian-like ancestors (synapsids).

[4][5] Acting as the first interface between the external environment and an animal's delicate internal lungs, a nose conditions incoming air, both as a function of thermal regulation and filtration during respiration, as well as enabling the sensory perception of smell.

In addition to acting as a filter, mucus produced within the nose supplements the body's effort to maintain temperature, as well as contributes moisture to integral components of the respiratory system.

Capillary structures of the nose warm and humidify air entering the body; later, this role in retaining moisture enables conditions for alveoli to properly exchange O2 for CO2 (i.e., respiration) within the lungs.

The sensitive cold receptors in the skin detect the place where the nose is cooled the most and this is the direction a particular smell that the animal just picked up comes from.

Amphibians also have a vomeronasal organ, lined by olfactory epithelium, but, unlike those of amniotes, this is generally a simple sac that, except in salamanders, has little connection with the rest of the nasal system.

The vomeronasal organ is well-developed in lizards and snakes, in which it no longer connects with the nasal cavity, opening directly into the roof of the mouth.

Since they generally have a poor sense of smell, the olfactory chamber is small, although it does contain three turbinates, which sometimes have a complex structure similar to that of mammals.

In some groups, however, including primates, bats, and cetaceans, the nose has been secondarily reduced, and these animals consequently have a relatively poor sense of smell.

The enlarged nasal cavity contains complex turbinates forming coiled scroll-like shapes that help to warm the air before it reaches the lungs.