As the migratory arthrothere grew even larger, some reached the point where they could live off of a purely carnivorous diet. With no competitors present, this population of large migratory arthrotheres settled down in East Glicker Tropical Coast. However, their size brings new challenges, as they are now so large that their prey can easily spot them. As a result, their behavior and morphology have changed greatly to circumvent these new problems, resulting in the euryptile.
The euryptile has become an ambush predator. Its spikes have atrophied away and its body has become dorsoventrally flattened, making it lie flat against the sea floor. Combined with its rusty orange coloration and sprawling legs, it is very hard for its prey to spot. Its antennae have moved down to the sides of its head so it can reach prey items with greater ease. Meanwhile, its eyes protrude from the top of its head, allowing it to spot unsuspecting prey. If a prey item wanders too close to the euryptile, it will either be grabbed by the euryptile's mouth or claws. Its mouth has become wide and short, allowing it to crush the tough exoskeletons of thornants, chunky knightworms, and migratory arthrotheres. It also feeds on more soft-bodied organisms, like the paralixo and coral cish.
The euryptile is also capable of swimming rather well. Its final segment has been split into several pieces, turning into a tail. Each of the nine segments that make up the tail correspond with a spike on its ancestor's abdomen. The final segment on the tail is a paddle-shaped telson, which provides propulsion when swimming. The fins on its hind legs have enlarged slightly, and aid in propulsion and steering. However, the euryptile rarely needs to swim, and only does so to find more favorable feeding locations.