What is a Clan Pokédex?
The Clan Pokédex in Pokemon Vortex is a living Pokédex of a clan, it records all the available Pokémon that can be caught. All the members of a clan can contribute towards the Clan Pokédex entries. The Clan Pokédex entries contribute to the total experience of the clan as well. If players are looking to increase their clan's total experience to push up the clan leaderboards, they must make sure that the Pokémon (which is gaining experience) is registered in their clan's Pokédex for it to be able to contrbute towards the total experience of the clan. Any member can contribute as many entries and there is no limit to how much one can contribute towards the Pokédex. Since multiple members are able to contribute towards one singular Pokédex, there are some factors that must be kept in mind before starting to complete it as the Clan Pokédex works a bit different compared to a singular player's Pokédex.
The Clan Pokedex is also categorised by region. The Pokemon of each region can be viewed in their respective tabs (Kanto -> Paldea + Vortex). The Clan Pokedex displays a total as well as a region specific completion percentage.

How to register a Pokemon
Catching on the Map
If a clan dex has an empty spot, it can be filled by catching the Pokemon on the map. Note that only one Pokemon can be caught per variant for the entire clan. If player A has it, then player B cannot register theirs without deregistering the first one.
Evolving Pokemon
If you evolve a Pokemon that is registered in the clan dex, the registration for that specific Pokemon is lost. For example, If player A has a Fuecoco that they evolve into a Crocalor, the clan loses the registration for the Fuecoco but gains the Crocalor registration (overall clan registration remains the same). However, if Crocalor was previously registered, then the clan loses the Fuecoco registration but gains none (overall clan registration goes down by one). If that same Fuecoco was to be evolved into a Skeledirge, one way would be to evolve the Crocalor first into Skeledirge and then evolve the Fuecoco into the Crocalor OR follow the seasonal stacking for evolutions.