The early whale ancestor from about 50 million years ago was Pakicetus, a wolf-sized mammal that still looked far more like a land animal than a modern whale.
Pakicetus lived during the early Eocene in what is now Pakistan. Its fossils were first discovered in 1981 in the Kuldana Formation, and the genus name means “whale from Pakistan.” It had four functional legs, a long snout, a robust tail, and toes adapted for walking rather than flippers. Its specialized inner-ear bones, however, revealed its close relationship to cetaceans.
Scientists once imagined Pakicetus as a strongly amphibious animal, but later skeletal studies suggest it was primarily terrestrial, perhaps wading or hunting near shallow water. Its teeth indicate it ate fish and other small animals. Pakicetus is therefore an important transitional form in the land-to-sea history of whales, though it was not itself a direct modern whale ancestor in a simple linear chain.
A common mix-up is with Ambulocetus and Rodhocetus. Those later whale relatives were more adapted to aquatic life, while Pakicetus retained the most obvious land-mammal features.