Modern cetaceans, the taxonomic group that includes whales, dolphins, and porpoises, evolved from land mammals. However, it has only been within the past few decades that transitional fossils have been found that have shed light on cetacean hindlimb reduction. DNA data suggest that cetaceans are most closely related to Hippos, which are even-toed ungulates. Other even-toed ungulates include deer, pigs, camels, and cows. Which statement describes most accurately how the early cetacean, Pakicetus, fossil ankle bones shown in the figure supports the hypothesis that cetaceans are closely related to even-toed ungulates?
A. The Pakicetus ankle bone suggests that Pakicetus most likely evolved from pigs.
B. The two humps on the bottom end of the Pakicetus ankle bone is a distinguishing feature shared with other even-toed ungulates.
C. This demonstrates that the early cetaceans had ankles 50 million years ago.
D. The Pakicetus ankle bone is most similar to other mammal ankles, suggesting a relationship between other mammals and cetaceans.