Bulljaw
Split off from the Common Roufo, the Bulljaw sought larger prey than its ancestor. Its jaw-spikes have calcified and fused with its lower jaw to form deadly serrated tusks, granting it a distinct bulldog-like appearance. This allows it to bite and tear into organisms larger than itself. It kills larger prey by latching on and thrashing about, slicing right through skin, bone, chitin, and the like with its serrated tusks, though calcified shells still give it trouble. It is still capable of consuming smaller prey through the same suction method as its ancestor as well. It is generally more tolerant of others of its kind than its ancestor, as a large kill can feed several Bulljaws.
The Bulljaw’s raptorial arm has been reduced to a fingerless nub on its underside. Its anal fin is forked, allowing it to move quickly to catch fleeing prey. Its middle anal phalanges and carpals, its anal metacarpal, and the vertebrae leading up to the anal fin have neural spines which create a raised ridge on the top and bottom of the fin, forming an “anal keel” which helps stabilize its attitude at higher speeds and strengthens the support of the fin.
To support its new hunting method and choice of prey, the Bulljaw’s teeth and jaw spikes are no longer pure keratin—they are calcified, like the baleen of terran whales, stiffening and strengthening them dramatically. This also makes them the hardest parts of its body, and potentially the most likely parts to fossilize. Like its ancestor, it mates by holding hands, pulling back the membranes which form its anal fin to free up its anal fingers for this purpose. It gives live birth to radially symmetric babies, which must follow their mothers and feed off of scraps until their jaws are developed enough for them to hunt on their own.