You are forgetting that a lot of animals look different when younger. For instance, a lot of sea animals start out as very small creatures, like a barnacle and crab. The larva is WAY different than what the adult looks like. In fact, larva barnacles actually are considered plankton as they swim and are carried by the ocean currents. It is only when they find a suitable place to land on (say a pier or a whale) that they attach themselves to that object (cementing their bodies) and metamorphosis into their adult form. Crabs look totally different too, with being plankton. Look them up on YouTube videos to see how different they are.

But yes, Coerul are feline-like creatures. They can be considered "kittens" as with the minion. Where does it say that they are pups?