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
Rough-toothed dolphin on rough-toothed dolphins are thought to include killer whales and sharks. Rough-toothed dolphins give birth to a single young, after an unknown period of gestation; it is also unknown whether or not they have a distinct breeding season. The young are about long at birth, and grow rapidly for the first five years of life. Females reach sexual maturity somewhere between six and ten years of age, and males between five and ten years. The population is not believed to be threatened by human activities. A small number of individuals have been harpooned by Japanese whalers and pods are also