http://www.edwardtbabinski.us/mpm/mpm_whale_limb.html
That's a link to a discussion of the vestigial pelvic girdle in the modern humback whale. I will look for earlier fossil pics with more developed systems.
From another source:
[What, then, does the fossil record reveal? Early whales, as exemplified by Ambulocetus natans, show well-formed fully functional hind legs. Two other whales--Indocetus ramani and Rodhocetus kasrani--appear later in the fossil record and show diminished although still perfectly functional hind limbs. Basilosaurus isis, finally, had very tiny hind limbs the utility of which is unknown. In the case of Rodhocetus, at least, where the pelvis is well-preserved, there can be no doubt but that the legs were attached to the pelvic girdle and that they were functional. As P. Gingerich et al note in their analysis of the fossil whale, "The pelvis of Rodhocetus articulates with the vertebral column by normal mammalian sacral synarthroses, meaning that Rhodocetus could support its body weight on land." ("New whale from the Eocene of Pakistan and the origin of cetacean swimming," Nature 368, 1994, p. 847). ]