The amniotic egg is a key evolutionary innovation of amniotes (reptiles, birds, and mammals) that allowed vertebrates to reproduce on land. It contains the amnion (fluid-filled sac protecting the embryo), chorion, allantois, and yolk sac. Sea turtles are reptiles and are amniotes. Frogs and fish are anamniotes (non-amniotes) that lay eggs in water; cockroaches produce an egg case (ootheca) but are invertebrates with no true amnion.