How are turtles related to tortoises?
Short answer: the tortoises are a subgroup of turtles that have specialized for life on land. Long answer: Typical tortoises belong to one family, the Testudinidae, distributed all over the world, but there are tortoise-like species that belong to other families. Consequently, their similar appearance is the result of (1) shared ancestry (e.g. the members of the same family) and/or (2) similar adaptations for similar habits and habitats. For instance, the box turtles also have a high-domed shell and are sometimes called tortoises, but they belong to a different family (Emydidae). For a terrestrial turtle, having a high-domed shell and pillar-like legs is better in terms of resistance to gravity and locomotion on land. Also, the shells of terrestrial tortoises usually have relatively thin bony scutes and thicker corny plates, so they’re not too heavy but very resistent. So these characteristics have evolved in different lineages of turtles and may result in superficial similarity. To an
