First shown on Wiglett Wednesday, but now it's official.
http://www.nintendoworldreport.com/news/61685/pokemon-unveils-divergent-species-wiglett-for-scarlet-and-violet
The newest Pokemon for Scarlet and Violet might have been confused as a regional variant, but is apparently an entirely new species.
The Pokemon Company have released a video showing off Wiglett, a new Water-type Pokemon. The bilateral (think worm) Pokemon is only known to possess Water Pulse as a move.
It is intended to be similar to Diglett - who appears in its trailer - but is capable of stretching itself in a way that makes it orders of magnitude longer than its buried counterpart.