Why Do Fish Have Vertical Tail Fins and Whales Have Horizontal Ones?

[MULTIZ321]

Why Do Fish Have Vertical Tail Fins and Whales Have Horizontal Ones?
By Yan Wong/ Nature/ Science Focus: The Online Home of BBC Focus Magazine/ sciencefocus.com

"Splish, splash! Fish and sea mammals have very different tails and methods of swimming.

It reflects the evolutionary history of locomotion. Our wormy ancestors slithered on the sea floor, so undulated side-to-side. Fish inherited that movement, for which a vertical tail is best.

Their distant land mammal descendants evolved to run with limbs underneath: an unstable gait allowing rapid direction changes. To extend the stride, their spine flexes up-and-down. Marine mammals kept this movement, for which a horizontal tail is best...."

Richard

 

[Sea Six]

The dolphin have horizontal tail fins, too. Reminds me of the time we were walking along the shoreline here on Marco, and the surf was a little rough. There was a school of young sharks feeding on bait fish right at the shoreline. Another lady and her friend were walking in the water and thought it was so cute, and commented how cool it was to see the dolphin feeding so close to shore. I said to her those are sharks, not dolphin, and you might want to get out of the water as they are feeding. They will be glad to chew your feet off. She saw fit to argue with me. I pointed out the tail fins on these fish are vertical and the dolphin tail fin is horizontal. She didn't have a clue. Damn tourist. Yes, it's OK to mess with a school of sharks in a feeding frenzy.

 

[T-Dot-Traveller]

My theory is :
Fish imitated the 1958 Plymouth
and
Whales copied the 1959 Chevy