As nouns the difference between tuatara and tortoise

is that tuatara is either of two reptiles, Sphenodon punctatus or Sphenodon guntheri, native to New Zealand, that resemble lizards while tortoise is any of various land-dwelling reptiles, of family Testudinidae, whose body is enclosed in a shell (carapace plus plastron). The animal can withdraw its head and four legs partially into the shell, providing some protection from predators.