Animalia paradoxa is not a real thing, it is a made-up term. It is used to describe animals that people think should exist, but they don't actually exist. It's like saying "What if unicorns were real?" But we know that unicorns are just imaginary creatures.
So, when people talk about Animalia paradoxa, they are talking about animals that they think would be very cool or interesting if they were real, but they are not. For example, some people might imagine an animal that has the head of a giraffe and the body of a lion. Or an animal that can breathe underwater and fly in the sky at the same time!
These animals are just "paradoxical" or "contradictory" because they don't follow the normal rules of what we know about animals. They are just fun things to imagine, but they don't actually exist in the real world.