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
White-toothed woodrat data provided by Macedo and Mares (1988) for what was then thought to be a single species applies to both. White-toothed woodrat Neotoma leucodon is a species of rodent in the family Cricetidae. Although originally named from San Luis Potosí, Mexico, as a species by Merriam, the white-toothed woodrat was long considered to be a synonym of the white-throated woodrat ("Neotoma albigula"). Molecular data, however, indicate the populations east of the Rio Grande in New Mexico and Trans-Pecos Texas represent a different species than morphologically similar populations west of the river. The habitat preferences of the two species appear similar,