Segmolixo
Splitting off from Paralixo is the Segmolixo, a creature very similar to its ancestor in its habits but which has elongated its body and gained additional fins by evolving and making use of repeating segmentation. This offers a number of advantages, such as letting it have more room in its stomach for food as well as the general maneuvering advantages that come with the extra fins. This also grants it many more bioluminescent spots, which in turn fill a greater role in sexual selection. It has also gained fibrous chitinous support structures in its fins and tail, helping it with swimming and “walking” on the seafloor, as well as allowing it to use its fins to help it dig. It has lost the fins that ran along its underside, as they were largely unused and only made it more difficult to move on the seafloor. It has also gained a pair of chitinous growths on either side of its mouth forming a sort of simple sideways beak-jaw, which it uses to help it break up tougher material such as dead worms and crystal flora into a size it can swallow. It has stopped seeing younger members of its species as food, as this was detrimental to its survival.
The repeating segmentation only grants the Segmolixo a total of 5 sets of fins; however, because they are all repeating segments, in theory a descendant could have any number of fins. Indeed, mutant Segmolixos with extra segments aren’t unheard of and live happy and healthy lives.
The Segmolixo is otherwise much like its ancestor. It is sexually dimorphic with males having brighter bioluminescent spots than females, it can switch its bioluminescence on and off to signal or to make itself less conspicuous, and when they mate, they do so multiple times over several weeks, with the female laying as many as 5000 eggs every few days. They typically stay near the seafloor, where their food—buried remains of dead organisms—is accessible. It digs for food using the shovel-shaped ends of its tentacles, as well as with its front-most fins.