Did whales have legs

No, the family of cetaceans that we call dolphins never had legs. However all modern cetaceans, including dolphins, share a common ancestor that had four fully developed limbs. This common ancestor lived between 45 and 50 million years ago and is now extinct, so it is known only through the fossil record.

The fossil record of cetacean evolution, of ancestral mammals transitioning from an amphibious to a fully aquatic lifestyle, is surprisingly thorough. The genetic evidence is equally compelling. Cetaceans have retained the genes for producing hind limbs, and their developing embryos still exhibit prototypical hind leg buds, that are reabsorbed before forming into full limbs. Rarely partial development does occur and a dolphin is born with vestigial hind limbs; a type of birth defect known as a atavism.