You were feeding fish to your pet Spinosauruses you had 3 of them. They would always jump up and down and pant just like a hungry puppy. When you were out on your boat going to feed them again. they were there but you saw something else in the water a big large snake like looking body came right up to your boat . It turned out to be a very large Mosasaurus. But it acted just like the Spinos did so well you decided to give it a big fish and it was certainly pleased. You already being attached to it called it Mosa for short.