Fig. 17
From: From Land to Water: the Origin of Whales, Dolphins, and Porpoises
Model of cetacean locomotor evolution as proposed by Fish (1996). Cetaceans probably followed the gray path on the left. The skeleton of Ambulocetus suggests that it swam by moving the hind limb and tail in dorsal and ventral undulations. Modern cetaceans undulate their tails dorsally and ventrally