Octopus and Spiders
Because of how octopus have 8 limbs, people think they're related to spiders. They're right but they aren't closely related. It goes back millions of years ago, back when spiders were still being evolved into what they are today while they were still crustaceans but what split them apart were the terms hard-bodied and soft-bodied crustaceans. Spiders were known as shelled organisms because they evolved to have a shelled exoskeleton to ward off predators while soft bodied are more flexible especially when escaping a predator. They were both from an 8-legged crustacean but no one is 100% sure what it was and how 8 legs originated from. 8 Legs VS. 8 Legs (It's funny because they're related): https://www.youtube.com/watch?time_continue=108&v=TplU3WNOggQ