Circulix impetus
As H. circumferus migrated to deeper waters, some went deeper still towards Zone 5. This was faciliated by the development of P. flotatortensis in Zone 5, the seeds of which were similar enough to replace their diet of P. forensus seeds.
Instead of four feet, C. impetus only has one. H. circumferus featured flatter and rounder feet, which eventually merged into one. Currents are stronger in Zone 5 than were experienced in Zone 12, so a better grip was necessary to stay in one place. The new foot cannot be used for locomotion, and acts only as a large suction cup. In order to move around, C. impetus uses two simple water jets on either side of the opening of its shell. It does so blindly, and relies on the ubiquitous presence of P. flotatortensis vines over the waters on Zone 5.
The cartilage plates of H. circumferus were lost, as they were no longer necessary due to the extinction of their only predator.
