Let's take a quick look at Shellmon and MoriShellmon!
While Shellmon lives by the sea, MoriShellmon lives by swamps in forests. That is also where its name comes from, with 森 mori meaning forest.
The Reference Book describes both of them as quite strong and agressive. Coupled with their "low intelligence", these are Digimon you can't reason with and might want to avoid stepping in their territory altogether.
Like many subspecies, MoriShellmon debuted in Digimon World as a recolor of Shellmon, in order to be able to easily tell partner and enemy Digimon apart. It was first featured in the anime in an episode of Digimon Ghost Game, over 20 years after its debut.
It was also featured in the Digimon Card Game. The artwork shows it in the Misty Forest, which is the area you can encounter them in, in Digimon World.
MoriShellmon BT5-051 by Tsunemi Aosa from BT-05 Booster Battle of Omni
