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
Toothed belt in their reinforcement. Toothed belts have two failure modes, one gradual and one catastrophic. There is an increased risk of either over the lifetime of the belt, so it is common for highly-stressed belts to be given a service lifetime and to be replaced before this failure can occur. One failure mode is gradual wear to the tooth shape, which may eventually lead to slippage over rounded teeth. The belt often continues to work, but the relative timing between shafts changes. The catastrophic failure mode is caused by delamination between the belt and its fabric reinforcement. Although this may be