Pokémon Go's new Trade Evolution mechanic is a cool nod to the main series

Last Friday, Pokémon Go released another menagerie of creatures from the Unova region - those originally found in DS games Pokémon Black and White.

But it also added a new gameplay mechanic - Trade Evolution - which is based on something found in the main games all the way back in Pokémon Red and Blue.

In the main Pokémon series, some creatures can only evolve when traded from one Trainer to another. It's something Pokémon Go has had to work around in the past - as trading was only added to the game later on.

Now, Pokémon Go offers this functionality too, sort of - and has backdated it to include Pokémon which in earlier generations evolved through trading in the main series games. This means creatures such as Kadabra, Machoke, Graveler and Haunter.

And it comes at the perfect time. New Pokémon from Unova added in this wave include Karrablast and Shelmet, which in the main series games can only evolve when traded with one another. Fun Pokémon lore fact - this is because Shelmet loses its suit of armour, which is then picked up by Karrablast for its own evolution.

In Pokémon Go, trading any of the species now marked with the Trade Evolution mechanic removes the full candy cost of evolving. You can still evolve creatures without trading, but it is heavily encouraged - both Karrablast and Shelmet require 200 Candy each to evolve otherwise.

All together, around 30 species were added to Pokémon Go at the weekend, including the rock-like Roggenrola, tadpole-like Tympole, crab-like Dwebble, garbage-like Trubbish, new bugs Venipede and Joltik, plus Shelmet and Karrablast. Fossil Pokémon Tirtouga and Archen, plus the Larvitar-like Axew are also available wild, although are rare spawns.

The Machop-like Timburr, which evolves into the top tier Fighting-type Conkeldorr, is a 10km egg and raid exclusive.

And there are a bunch more Pokémon which are now available as regional exclusives. Throh and Sawk are divided across the world along the usual Solrock/Lunatone and Zangoose/Seviper lines. The pirannah-like Basculin has two colour forms split across the Greenwich Meridian line, just like Shellos.

Finally, Sigilyph is available in/around Egypt and Greece, while the cacti-like Maractus is available in the Southern US, Mexico, Central America, the Caribbean and South America.