Extensible Pokédex Order

The Extensible Pokédex Order (XPO) is a new standard for the National Pokédex that groups related Pokémon species. Hence the name, this order is intended to accommodate new generations of Pokémon in a consistent format.
It is a response to certain perceived problems with the current numbering system and its immutability. Mainly, some related Pokémon are strewn across the National Pokédex, such as the evolutionary line of Mime Jr. (#439), Mr. Mime (#122), and Mr. Rime (#866). Another problem is that Nidoran's gender differences remain split into separate evolutionary lines. The Extensible Pokédex Order solves such problems by shifting the focus to families of related Pokémon, groups that can be amended to include new relatives.
Under this system, families of Pokémon are ordered by first instance of their first member. A Pokémon's family includes its other evolutionary stages, regional forms, and certain breeding relationships (namely the Nidoran lines, Volbeat and Illumise, and Manaphy and Phione). The number given to each family starts with an X, distinguishing it from a species Pokédex number, and does not use leading zeroes. If a species must be referred to within its family number, Roman numerals (and the Greek letter beta, for Baby Pokémon) can specify evolutionary stage.
Category:Pokémon (series)
Category:Lists