Whales evolved from sea lion-like ancestors that returned to the sea. We do not know what the whale’s land-dwelling ancestors looked like. Early whales were mostly like huge dolphins or killer whales. One of these, called Basilosaurus, was a slender predator about 21 m long.

            Fossil remains of whales are very scarce and not much is known about these animals. The early forms did not have the echo-sounding ability of modern whales and dolphins, which did not evolve until much later.

                They are thought to have swum with an eel-like motion and may not have propelled themselves with the flattened fluke found in modern whales. Some early whales still had rudimentary hind legs, but these were so small that they could not have played any part in swimming. When whales die their remains usually sink in deep water where they are unlikely to form fossils.

Picture credit: google