The earliest turtles evolved during the Triassic period, but they probably could not withdraw into their shells like modern turtles. Lizards and snakes have poor fossil records. This is probably due to the animals’ tendencies to live in dry uplands, far from the areas that are most likely to produce fossils (most animal bones survive if they are quickly buried with sediment, such as along riverbanks). It is thought that lizards appeared in the Late Triassic; the earliest remains of snakes are found in the Late Cretaceous (in North America and Patagonia, South America).