From publisher blurb:
Welcome to Rasmussen’s Guide, a tool for those wanting more science in their science fiction.
It is for GMs running campaigns who need an alternate world with a logical ecology. Admit it, game worlds need internal logic, after all. Living animals do not spontaneously generate from nonliving matter, nor do they magically appear out of thin air. All living things metabolize, reproduce, grow, and adapt. They do not do these things in a vacuum. This planetary guide is a concise look at these lifeforms as they might evolve on a variety of planets, moons and celestial objects, using each world’s surface gravity to define its primary vertebrate Superclass and maximums.