Cetacea and two (external) limbs that are modified into flippers. Though not as flexible or agile as seals, cetaceans can swim very quickly, with the killer whale able to travel at in short bursts and the fin whale able to cruise at . Dolphins are able to make very tight turns while swimming at high speeds. The hindlimbs of cetaceans are internal, and are thought to be vestigial. Baleen whales have short hairs on their mouth, unlike the toothed whales. Cetaceans have well-developed senses—their eyesight and hearing are adapted for both air and water, and baleen whales have a tactile system
Spade-toothed whale to an oversized ginkgo-toothed beaked whale in overall shape, as their skulls are quite alike except in size. The distinguishing characters are the very large teeth, , close in size to those of the strap-toothed whale. The teeth are much wider than those of the strap-toothed, and a peculiar denticle on the tip of the teeth present on both species is much more pronounced in the spade-toothed whale. The common name was chosen because, in life, the part of the tooth that protrudes from the gums (unlike the strap-like teeth of strap-toothed whales) has a shape similar to the tip