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
Captive killer whales twice that length or and a minimum depth of , giving a minimum volume of for two killer whales. Each additional killer whale requires a pool with an additional of volume. 9 CFR 3.104 also requires a minimum of surface area per killer whale in Table IV (the example with a cylindrical tank in diameter for two whales provides of surface area per killer whale). Swiss regulations require a larger minimum volume: × deep for two killer whales, or . The Alliance of Marine Mammal Parks and Aquariums (AMMPA) goes further, and recommends for two killer whales. The US exhibitors