The flunejaw split from its ancestor the grubby flune. In the absence of any land-based predators in Chum Temperate Riparian, the grubby flune was able to fill the niche. Becoming a full-time carnivore, rather than an omnivore, it’s jaw became more powerful to aid it in ripping flesh and cracking the shells of kruggs and their descendants. With the rise in temperatures following the solar flare, the grubby flune lost much of its protective fat layer, allowing it to move more quickly. The plates on its back are also further apart, for ease of mobility, as they are less needed for protection in its position as apex predator.
Despite its increased maneuverability, the flunejaw still is not terribly fast and is mainly an ambush predator. It lurks within the stands of saltgrass and segmented carnoferns or in shallow water by the riverside, waiting for a suitable prey fauna to come along. When one is spotted, it darts out of hiding, grasping the unfortunate fauna with its powerful beak to drag it away.