What family includes all living tortoises?

The family that includes all living tortoises, in the usual taxonomic sense, is Testudinidae.

Testudinidae is the tortoise family within the order Testudines. Its members are generally terrestrial, slow-moving reptiles with sturdy, domed shells and column-like limbs adapted for life on land. The family includes familiar animals such as the Galápagos giant tortoise, Aldabra giant tortoise, African spurred tortoise, and many species of Testudo.

The name can cause confusion because “tortoise” is a common word whose use varies by region. In standard zoological classification, Testudinidae refers to the family of modern land tortoises. In some British and international usage, however, people may call other land-dwelling turtles “tortoises” informally, even when they belong to families such as Geoemydidae. That linguistic variation does not change the canonical quiz answer.

Tortoises are part of Cryptodira, the turtle group that generally retracts the head straight backward. Their shells consist of a domed carapace and a lower plastron, while their diets are usually based on grasses, leaves, flowers, and fruit. Several lineages independently evolved giant body size, including the Galápagos and Aldabra tortoises.