The story of whale evolution is amazing. It’s a story of how small, terrestrial mammals living in and around what is now Pakistan became the largest animals ever to have lived on Earth. Ambulocetus is an integral part of this story.
Ambulocetus, or the “walking whale,” was a strange-looking 10-foot-long cetacean from the Eocene Epoch some 45 million years ago that could both walk on land and swim proficiently.
Ambulocetus is a transitional form, or what some people call a “missing link.” This amphibious mammal connects the more distant ancestors of whales like the mostly terrestrial Pakicetus with more recent fully aquatic relatives like the humongous basilosaurids.
Although Ambulocetus could walk on land, the structure of its feet seems to indicate that it was more suited to life in the water, where it got around undulating its back like sea otters do today. Not only did this Ambulocetus have a skull and teeth resembling other whales but it also had an adaptation in its nose allowing it to swallow underwater and ear bones showing some adaptations to aquatic life.
Modern whales have refined adaptations for their lifestyle including nostrils on the tops of their heads, tail flukes and two big flippers for propelling themselves through the water. One amazing vestige of whales’ heritage lies buried deep in the tissue of their hind region. Whales have remnants of a pelvis, a sign that cetaceans evolved from four-limbed terrestrial ancestors.
