If you're a fantasy author/game designer and want to create interesting and biologically believable worlds without resorting to tired Tolkienisms like dwarves, halflings or horses, you need to be reading 'Science of Creature Design' and 'Animals Real and Imagined,' by Terryl Whitlatch. She served as the lead creature designer on Star Wars Episode I: The Phantom Menace and created most of the iconic aliens and animal designs we see in that film. Fantasy fiction is a realm of limitless imagination. You should have no excuse not to create original creatures rather than endlessly importing borrowed ones.