The family Chelidae, commonly known as Austro-South American side-necked turtles, belongs to the order Testudines. These turtles are characterized by their distinctive method of retracting the head sideways under the shell rather than pulling it directly back. Chelids are primarily freshwater species, inhabiting rivers, streams, swamps, and lakes across South America and Australasia. They exhibit a variety of diets, ranging from carnivorous to omnivorous, feeding on fish, invertebrates, and plant matter. Many species have flattened, streamlined shells adapted for aquatic life, and some show remarkable longevity. They play important roles in their ecosystems as both predators and scavengers and are often of conservation concern due to habitat destruction and exploitation.