and moves in the water at night. It lays its eggs on the land; male and female take turns guarding them. Certain fish with saw-tooth backs [ dolphins ] kill them by cutting their soft bellies. The crocodile is the only animal that moves its upper jawbone. Guillaume le Clerc [13th century CE] ( Bestiaire ): The crocodile is a fierce beast that lives always beside the river Nile. In shape it is somewhat like an ox; it is full twenty ells long, and as big around as the trunk of a tree. It has four feet, large claws, and very sharp teeth; by means of these it is well armed. So hard and tough is its skin, that it minds not in the least hard blows made by sharp stones. Never was seen another such a beast, for it lives on land and in water. At night it is submerged in water, and during the day it reposes upon the land. If it meets and overcomes a man, it swallows him entire, so that nothing remains. But ever after it laments him as long as it lives. The upper jaw of this beast is immovable when it eats, and the lower one alone moves. No other living creature has this peculiarity. The other beast of which I have told you (the water-serpent), which always lives in the water, hates the crocodile with a mortal hatred. When it sees the crocodile sleeping on the ground with its mouth wide open,