I've heard that you can only have an creature as small as a hamster or as big as an African Elephant. I think that maybe it isn't true (I mean, its an Evolution-involved game for crying out loud! Shouldn't you be able to make at least a T-Rex Sized creature!?) I actually have four species I want to try to make when I get the game. A Velociraptor-ish creature that has three eyes, a creature that looks like a cross between a clam and an elephant, an aquatic giraffe (i.e. flippers instead of feet and legs) and a Twi'Lek like creature. They kind of encompass different types of animals, the raptor-ish one a carnivore, the clam/elephant as an herbivore, the aquatic giraffe a swimming creature, and the Twi'Lek-like a humanoid.