Shellback Prickworm

A small group of cave prickworms wandered out of the Darwin Water Table and into Chum Temperate River. It's legs evolved into fins and it contracts into its shell for hibernation until it is time to mate. After hibernation, the shellback prickworm then licks clean its 'filter horns' and swims upstream to mate, after which it hibernates again and floats downstream. It generated a thick shell made of overlapping, flat plates to protect against predators like the elegant emperor phibisian. The shell is made of plates so that if one layer is penetrated it will still have protection. The elegant emperor phibisian is especially a problem as a predator because it has no problem swimming unnoticed by the shellback prickworm as it is hibernating.The flunejaw is also a sizeable threat because it eats the shellback prickworm out of the water from the shore as it swims upstream. When the shellback prickworm hatches, it has a full shell and gradually loses its plates as it ages. This allows the shellback prickworm to lay less eggs because more will survive to adulthood due to the increased protection of their young. It also restored some pigmentation to ward off harmful UV radiation. The shellback prickworm swims upstream by rippling its tail and paddling with its fins.