Simply put, all animals are and always have been pokèmon. Real world terms such as dog, canine, cat, fox, feline, fish, ect. may be used as descriptors that identify types of pokèmon that share similar biological features, but there are no dogs/cat/ect that are not pokèmon. That being said, it is also assumed that there are many more pokèmon known in the world than the ones identified by the games. Obviously there are more than 649 known species in the world (since all animals are included in this category and many of the pokèmon themselves would not be considered animals). However, we will not create additional pokèmon on site. Instead, if there is a reason a member may wish to reference some animal that no known pokèmon are quite suited for, it is appropriate to refer to them vaguely. For example, say in a character's history they had some sort of dog, but you are not satisfied with any of the wild/strictly elemental varieties, and the Houndoom and Herdier lines do not suite, 'dog pokèmon' can be used instead. Similarly 'fish pokèmon' maybe caught for eating or catch and release, when none of the known fish pokèmon fit the needs of the scenario.
Information quoted from Christofs 'Important Information' thread in the Join section, found HERE.