When discussions about evolution occur, one of the frequent criticisms is that there is often scant evidence showing the transition of an animal from one form to another. Given the rarity of fossils, this is a clever argument, but often lacking in any real merit. Now, one has been found that appears to show the transitional form from a walking, land-based mammal to pinnipeds (the group that includes seals, sea lions, and walruses). The animal, Puijila darwini, had a long tail and otterlike body with both webbed feet and legs like a terrestrial animal. However, it had a pinniped-like skull and a body that is a meter in length. It is estimated that it lived 22 million years ago, and the skeleton suggests it was adept on both land and in the water.