After the extinction of the flash cells, the lightvesting filtersquid was forced to rely entirely on their filterfeeding to survive. But do to depending on them for certain nutrients, the surviving organisms were sickly and malnourished, living only about a fourth their usual live spans. They were on the brink of extinction until the hardened flash cell was introduced into the environment. Being so closely related to the flash cell, they were easily incorporated into their physiology. Because they were malnourished, their young tended to have wild mutations. When they were provided with the much needed nutrients from the hardened flash cells, the mutants were able to survive long enough to breed, creating an armsrace that lead to a new species that replaced it's ancestor.
The finned filtersquid's tentacles have become less flexible, being used to bend inward and outward, helping propel them through the water in a bell motion. They have also added fins to the sides of their body frames and in between their tentacles to help in propulsion. Their fins have evolved into claw like protrutions that focus the water into a smaller point, moving them farther for less energy.