But when the first turtles moved from the land to the sea more than a hundred million years ago, they didn't have this ability, says Ren Hirayama, a paleontologist at Teikyo Heisei University in Chiba, Japan. The little turtle, barely eight inches long, was probably a young adult. Hirayama noticed that the bones in its limbs were not fused into rigid paddles as they are in living sea turtles. The fossil turtle had movable digits, like a freshwater turtle's. When swimming in salty seas, a marine animal with land ancestry runs the risk of dehydration because its body fluids are much less salty than the surrounding water.
Sea turtles have large tear glands that concentrate salt and shed it in huge, salty tears.
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