<Tr> <Th_colspan="2"> Type species </Th> </Tr> <Tr> <Td_colspan="2"> Testudo graeca Linnaeus, 1758 </Td> </Tr> <P> Tortoises (/ ˈtɔːr. təs. ɪz /) are a family, Testudinidae, of land - dwelling reptiles in the order Testudines . Tortoises are shielded from predators by a shell . The top part of the shell is the carapace, the underside is the plastron, and the two are connected by the bridge . The carapace is fused to both the vertebrae and ribcage, and tortoises are unique among vertebrates in that the pectoral and pelvic girdles are inside the ribcage rather than outside . Tortoises can vary in size from a few centimeters to two meters . They are usually diurnal animals with tendencies to be crepuscular depending on the ambient temperatures . They are generally reclusive animals . Tortoises are the longest living land animal in the world, although the longest living species of tortoise is a matter of debate . Galápagos tortoises are noted to live over 150 years, but an Aldabra giant tortoise named Adwaita may have been the longest living at an estimated 255 years . </P> <P> Differences exist in usage of the common terms turtle, tortoise, and terrapin, depending on the variety of English being used; usage is inconsistent and contradictory . These terms are common names and do not reflect precise biological or taxonomic distinctions . </P>

How old can a tortoise live to be