Actually, you can call whales fish (it's not like there's a common ancestor of all fish of which whales aren't a descendent) they just also happen to be mammals

Actually, you can call whales fish (it's not like there's a common ancestor of all fish of which whales aren't a descendent) they just also happen to be mammals. https://en.wikipedia.org/wiki/No_Such_Thing_as_a_Fish https://en.wikipedia.org/wiki/No_Such_Thing_as_a_Fish