Nautipede

When the pressures of predation became too great, the jumping shellpede needed a better way to survive, so they floated upward. The nautipede arose from this. While it's ancestor still survives below, the nautipede spends it whole live in the sunlight zone.

The nautipede has modified the air bladder of it's ancestors to control it's buoyantcy in the water. It has also retro-evolved its claws back, which It uses to steer. Because the nautipede moved to a different area, the malakommalis has evolved into a different spieces, The shelommalis. The two live in symbiosis. The nautipede gets protection and the shelommalis gets distribution.

The nautipedes formed a symbiotic relationship with shelommalis. When the nautipede eggs are eaten by a creature, shelommalis spores infect the helpless creature, which is then poisoned and dies. Then the eggs hatch in the corpes. The young stay their, feasting on the body until their shells become thick enough, then the float up to the sunlight zone and switch to a herbivorious lifestyle.