10 Animals We Know Today Look Completely Different From Their Ancient Forms

Modern animals can make evolution appear visually predictable, but the fossil record reveals experiments in size, movement and anatomy that no longer exist. Familiar groups once included walking whales, bear-sized rodents and crocodile relatives built more like racing dogs.

These extinct species were not always the direct ancestors of living animals; many occupied neighbouring branches of the same evolutionary family tree. Their fossils nevertheless demonstrate how dramatically successful animal lineages changed as climates, habitats and available food shifted.