Yes, crazy as it sounds, but whales, specifically baleen whales, or whalebone whales, do have an arm, hand, and fingers in their flippers. And they’re real bones made out of calcium, although a little softer.
They also have a skull, a backbone, a rib cage, and a hind leg. Sounds mutant to me.
Their skull can grow as big as 14′ long, with teeth on the lower jawbone, that are the biggest teeth of any animal in the animal kingdom.
So when you’re swimming around in the deep dark sea, watch out for those bones!