The Eumetazoa make up almost all animals, except sponges and a few other animals without legs, fins, or tentacles. In this key, only the one with appendages are included. Since it's easy to assume something can't fly (such as a chicken), we're including flying things in this key. Some of these animals have a skeleton on the inside, others don't.
a. It has bones and no exoskeleton (Subphylum Vertebrata)
b. It has no bones, and it may or may not have an exoskeleton