Cetacea toothed whales and two in baleen whales. The nostrils are located on top of the head above the eyes so that the rest of the body can remain submerged while surfacing for air. The back of the skull is significantly shortened and deformed. By shifting the nostrils to the top of the head, the nasal passages extend perpendicularly through the skull. The teeth or baleen in the upper jaw sit exclusively on the maxilla. The braincase is concentrated through the nasal passage to the front and is correspondingly higher, with individual cranial bones that overlap. In toothed whales, connective tissue
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,