Fun fact: snakes belong to the lizard family (Squamata), and evolved from what can be scientifically called lizards. So by all means, they are legless lizards – one of many lizard groups that lost their legs, in fact.
Tuataras on the other hand may look a lot like lizards, but they’re not. They’re Rhynchocephalians, an ancient group of reptiles that appeared even before lizards evolved and experienced great diversity, but now are represented only by the two species of tuatara surviving in New Zealand.