1. Shell: The most distinctive feature of a tortoise is their hard and protective shell made of keratin, which is divided into two parts, the carapace and the plastron.
2. Longevity: Tortoises are known for their long lifespan, some species can live up to 150 years.
3. Slow metabolism: They have a slow metabolism which allows them to survive on limited resources like water and food for long periods.
4. Claws: Tortoises have sharp and long claws that help them to dig burrows, climb rocks, and even defend themselves.
5. Dry habitat adaptation: Tortoises have adapted to living in dry habitats, they can get a majority of their water requirements from their food or survive without drinking water for months.
6. Ability to retract their limbs: Tortoises can retract their limbs, tails and heads inside their shells to protect themselves when threatened.
7. Herbivorous diet: Tortoises are herbivores and feed mainly on grasses, leaves, flowers, and fruits, and their digestive system is adapted to break down tough plant fibers.
8. Large size: Some tortoise species like the Galapagos tortoise are among the largest reptiles in the world.