The Evolution of Whales: When Whales Had Legs
Millions of years ago, before they were sleek, tail-powered swimming machines, whales had legs. They once strode on land on four appendages, just like mammals today, and moved freely between land and sea. Over time, as they evolved into the water-dwelling creatures that we now know and love, their front legs became flippers while their back legs and hips disappeared almost entirely.
I say almost, because all modern whales still retain traces of pelvises, and every now and then one is born with a leg or two—a throwback to the land-loving days of whales.
The 4-legged (plus tail) whale on the bottom, Georgiacetus, cruised the Gulf of Mexico 40 million years ago, when sea levels were 130 feet higher than they are now. It reached some 12 feet in length and used its sharp teeth dine on squid and fish. Amateur bone hunters found the fossils along riverbanks in Alabama and Mississippi, some 98 miles inland from the modern coastline.
According to paleontologists, Georgiacetus was one of the last whales to have a tail and powerful hind legs, used its large back feet like modern whales use their tail flukes—to swim in an undulating, wave-like fashion—and is the missing link in the evolutionary chain of whales.
The first known whales to have flukes appeared around 38 million years ago, so it only took 2 million short years for whales to ditch their legs and made the final transition from land to sea.