Evolution of cetaceans "Caperea marginata") all have derived characteristics presently unknown in any cetothere and vice versa (such as a sagittal crest). The adaptation of echolocation occurred when toothed whales (Odontoceti) split apart from baleen whales, and distinguishes modern toothed whales from fully aquatic archaeocetes. This happened around 34 million years ago in a second cetacean radiation. Modern toothed whales do not rely on their sense of sight, but rather on their sonar to hunt prey. Echolocation also allowed toothed whales to dive deeper in search of food, with light no longer necessary for navigation, which opened up new food sources. Toothed whales
Spade-toothed whale initially remained undescribed, but was later believed to be from a ginkgo-toothed beaked whale. In 1986, a damaged calvaria was found washed up on Robinson Crusoe Island, Chile, and was described as a new species, "Mesoplodon bahamondi" or Bahamonde's beaked whale. In December 2010, two specimens, a cow and calf, were found stranded on Opape Beach, Bay of Plenty, New Zealand. They were originally identified as Gray's beaked whale, but later genetic analysis revealed that they represented the first complete specimens of the spade-toothed whale. Following this find, a report describing the spade-toothed whale and an analysis of their DNA