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Ambulocetus

Ambulocetus

Fossils of a huge three meter long mammalian "crocodile" (Ambulocetus), also from this time period, have been found in Pakistan. They could walk on land, but were better adapted to swimming in water. They probably hunted by lurking in shallow water and then ambushing prey as it came down to the water to drink (true crocodile style). They probably swam like an otter or whale, undulating their backs vertically. It is thought to be a transition fossil, representing one of the first mammals that went back into the water, and as such it is regarded as a predecessor to modern whales. (Ambulocetus literally means "walking whale") They share their ear structure with whales, which would have enabled them to hear under water by picking up vibrations. They also had an adaptation in their nose that allowed them to swallow underwater and their teeth are similar to dolphins and whales. Chemical analyses of their teeth suggest that they were at home in salt as well as freshwater. (3) (Pakistan then was on the coast of the shallow Tethys Ocean. Many early whale fossils have been found in the remains of this once seabed, which suggests that the warm shallow Tethys might have been the cradle of the evolution of the whales.)