The Zoanoid referred to by the derogatory name "Marmot" is a prototype power-class Zoanoid developed by Cronos Japan. Only one is ever seen in the Guyver series, having escaped Cronos before his optimization was completed, severely reducing his lifespan. As he fled Cronos Japan, Marmot stole the top-secret Guyver units, hoping to trade them to a traitor within the organisation in exchange for having his humanity restored. What he never learned, however, was that Zoanoid optimization is irreversible.
Marmot fled into the woodlands surrounding Mount Narisawa with the three Guyver units, but Cronos sent their agents after him and cornered him. With no way out, Marmot brandished a grenade and set it off, killing himself and scattering the G-units.