Some in the line were strange-looking, none more so than the Basilosauridae, who appeared in the middle-to-late Eocene periods (about 38 million to 40 million years ago) and were found in all the world’s oceans. They were probably the first fully aquatic cetaceans. They were also extraordinarily long creatures, with spines that extended fifty feet and longer, while their limbs shrank to just the tiniest vestigial rear feet and small forelimbs near the head that scientists speculate were used
Basilisauridae
