Xenocranium
Xenocranium lived during the Eocene epoch, 55 million to 34 million years ago. It had a skull tipped with a broad scoop, which it likely used for digging. In fact, its entire skeleton, with its short, strong limbs, was specialized for burrowing.
Livyatan melvillei
The gigantic extinct sperm whale Livyatan melvillei measured a whopping 60 feet (18 meters) in length. It had huge curved teeth lining its upper and lower jaws — unlike modern sperm whales, which grow conical teeth only on their lower jaws.