https://www.cnet.com/news/oddball-ancient-whale-had-four-legs-hooves-on-its-toes/ > The Natural History Museum in the UK describes the animal as a "semi-aquatic proto-whale known as a protocetid." The skeleton dates to the middle Eocene, 42.6 million years ago. > This illustration shows the swimming and walking positions of Peregocetus pacificus.