The boneripper replaced the kelpiesaur in the area around the Bone Swamp, but its ancestor still lives in the rest of the river.
The boneripper gets its name for a good reason. When it started moving to the swamp, it had to compete with its own ancestor, as well as the bloated serpentsaur, turtsnapper, and mudworm as the top predator. Thus, its brain got bigger, and it expanded its diet so it could live longer without eating as much meat. Eventually, after the kelpiesaur went extinct in that particular part of the river, its larger brain helped it to get some new tactics for survival.
It is now able to eat most anything in the Bone Swamp, aside from the tough (but thankfully slow) turtsnapper. It developed incredibly powerful muscles, lithe yet strong, like corded steel. With this power behind its grip, it can now catch things like the mud-spike, mudworm, and fin worm, with lightning fast grapples, then with its powerful muscles, it actually rips off body parts until its prey is dead. For things like the mud-spike this is especially important, as its razor blade on the fin could be deadly. It will then carefully remove anything hindering digestion (spikes, carapace) so that it can eat the fleshy insides.
For the bloated serpentsaur it has a completely different method of hunting. When it sees any of the black swampshrooms (whether or not they are serpentsaurs in disguise) it will carefully approach it, extremely slowly, looking for any movement. If it sees none (or perceives none) it will cautiously grab the cap of the shroom with its claws, Obviously, if it simply a plant it will do nothing. If it is a serpentsaur it will be in extreme pain. When the flailing creature lets go its deadly tail the boneripper will let go quickly, leaving the confused animal to either stab itself, or miss and leave itself open for the boneripper to grab its tail, rendering it useless and doomed.
Like its ancestor it travels in communal groups. These groups will wander around, the males (save a few) looking for food to bring back, the females guarding the eggs and young. The females at night will dig crude nests in the mud to rest, and for the young to wrestle and play. They have completely different nests for the eggs, which are set aside so they are not damaged (or accidentally eaten by hungry infants). Because it now spends much more time on land than in water it has lost its webbing and fins (though it can still swim well, just not quite as well).