Eight new sprites were leaked by Chrales, a data miner with impeccable track record of discovering new sprites and features in Pokemon GO’s network traffic. Charles shared that four new Pokemon species now have proper sprites that are downloadable by the game.
The sprites include the following Pokemon families:
Curiously, two of these Pokemon are evolutions from previous Pokemon generations (Yanmega and Tangrowth), which makes this leak particularly interesting. Maybe January or February could be themed as “nature reawakening” months and introduce these two Pokemon.
Additionally, with Yanmega and Tangrowth sprites now available, all cross-gen Pokemon that evolve in Generation IV now have normal and shiny sprites. Although only a handful are released so far, all of them are eligible for release at any moment.
— Chrales (@Chrales) December 6, 2018
For more information on these Pokemon, we strongly recommend you read our Sinnoh Stone: best Pokemon to use Sinnoh Stone on guide and search for their overviews on Pokemon GO Hub.