Gigantospsari

Few million years after the appearance of gnathospsari, the Deep sea vents became more and more crowded. As few polypods and other micro planktons left the biome in order to venture to the open sea, gnathospsaris followed. They were named Gigantospsari, meaning big fish

In the depth of 500-2000 meters below sea level, because of the scarcity of food, one of the clades of gnathospsari adapted highly sensitive chemical sensers, (the pinkish line across the body). The mechanism is simple: adapted chemo-sensers around its body can detect prey kilometers away. Due to high concentration of blood, this part looks pinkish.

The clade also developed a revolutionary body plan: bioluminance and eyes. Since none of the clade actually have eyes, private communication between individual became possible. This meant development of more complex brain; however, due to amount of energy brain required, it couldn't get as efficient. Therefore the creature can only communicate simple emotions: mating and warning. If there were more food available, these creature might have developed better social system.

Finally, the lower fin was used for 2 purposes: moving and breathing. The fin can be moved to turn directions easily. Accompanied by powerful tail, this "fish" became the fastest animal on the planet. (15km/h) It also had secondary gills attached, therefore getting oxygen became easier. However, because of that. Once broken, gigantospsari is likely to die.