Snails are shelled gastropods that appeared in the late Cambrian period, about 480 million years ago, and are still alive today.
The body of snails is divided into two parts – the shell and the soft body that supports it. Most snails with shells have a single-piece shell, usually coiled or spiral. This coiled shell usually opens on the right side. Many species have an operculum, which in many species acts as a trapdoor to close the shell. This is usually made of a hard, sometimes calcareous material. In land snails, the shell is smaller or even absent. The rest of the snail's body is soft, with a viscous texture and dark colors, sometimes ornamented with light-colored spots. They lack legs, but they move thanks to a "muscular ventral foot". The foot has a wave-like movement produced by muscle contractions that contribute to the process of "gliding", while a slippery mucus is secreted that reduces friction on the surface on which the snail moves. This mucus is the "trail" that land snails leave behind as they move.
Snails have evolved a wide range of diets, with species including herbivores, carnivores, omnivores and detritivores (animals that feed on decaying plant and animal matter). Some species consume worms, plants, rotting vegetation, animal waste, fungi or other snails.
