The kelpiesaur evolved from and replaced the lindsaur and continues its amphibious lifestyle. It has spread throughout the Bone River and not just in Huggs Rainforest. Its fingers have fused together again, giving the kelpiesaur jointed arms. The fins down its back have almost completely disappeared. The tail spikes have likewise further atrophied. The webbing from the body to the last finger has further developed, acting as a large fin. The kelpiesaur's coloration has changed to better camouflage in the muddy waters of the river. It is somewhat larger than it's ancestor. Its ears have developed further and it now hears quite well in both air and water, despite being sealed while submerged. The kelpiesaur's lungs and heart have also improved, allowing it to hold its breath longer underwater and sustain more activity.
The kelpiesaur has become quite social and lives in family groups. Male and female kelpiesaurs will mate for life, while the young will stay with them until they reach a certain age. Young males will leave their family to find a mate, while young females stay with the group and will only leave once they has become a male's mate. A newly paired couple will build a den at the edge of the river and will then mate. The young are cared for by the adults, this includes bringing them food and teaching them how to hunt. Young kelpiesaurs will often help the others in their group by eating soriparasites off of them.
The kelpiesaur hunts prey in the water and also ambushes animals on the banks of the river. Family groups will often hunt as a team. Sometimes a young kelpiesaur will use itself as bait to lure a predator near the water where it will be ambushed by the rest of the family. It will also eat carrion that it finds.