But land animal would have to be a liger sea animal- Squid, I heard they are basically almost genius air animal- Crows, they are the smartest bird alive :P
Best land animal-Hard one but Monkey.They seem so awesome when not flinging poop. Best sea animal- Easy Dolphin.The are intelligent. Best air animal- Hummingbird.Their wings are awesome.
For the carnivore I'd go with sharks. Their ability to sense preys and blood underwater, their streamlined morphology and their speed, their rows of teeth that are constantly replaced... Sharks would even count for present and past species
Land: Monkeys, they're just hilarious. Sea: Dolphins, they're something that interest me, something I'd like to learn more about. Air: Toucans just look cool.