Why do marine mammals., whales, dolphins, etc., have horizontal tails while gilled fish have vertical tails?
Awesome friggin question! I had only a partial answer, and had to look the rest up. Mammals developed on land, long after life had left the seas, and then returned to the waters…that’s why marine mammals have hair and give live birth, breathe air and have and do so many things that seem disadvantageous to life in the water. I suppose that the answer someone else gave about being able to surface quickly MIGHT be correct, and in fact the reason has a lot to do with the way animals move. Fish propel themselves by moving their skeleton side to side, and so the fin is best used when it is vertical, since it is being waved left and right against the water. Mammals, on the other hand, developed musculature and skeletal structures best adapted for moving on land so they move up and down. You see this in the way dolphins and whales swim, and the way walrus, seals and sea lions move on the ground. The fin is better adapted for this up and down motion because of its horizontal positioning. In t
