Anthrometamorphic
Any of a mythological species of anthromophic (animal with human characteristics such as the ability to talk, the ability to walk up-right, and physical human like anatomy) creatures with the ability to morph between anthromorphic form and original animal form. An example would be the mythical werewolf, able to change from wolf to anthromorphic werewolf under a full moon.
Many creature from ancient mythology were anthrometamorphic, such as the werewolf, Dracula, and Medusa.