The Beastbull split from its ancestor and became dramatically larger. With the advantages granted by its jaws, it is able to prey on comparatively massive filter-feeders such as the Filterclad, a niche inaccessible to the jawless organisms in its environment. When hunting small prey, its method is similar to before; however, when hunting a filterclad, several individuals may gather with their eyes set on the same prey. They essentially attack as a disorganized mob and share the resulting feast.
The Beastbull is slower than its ancestor to conserve energy in the abyss, but it can accelerate quickly to catch motile prey before it can flee. It can see into the ultraviolet range, which allows it to easily detect its bioluminescent prey; inversely, its skin absorbs light in the UV spectrum, which makes it invisible to its prey against the dark abyssal backdrop. It also has electroreceptors in its snout, which allow it to easily detect smaller prey passing by. It eats smaller prey by sucking it into its mouth, much like its ancestor. In the midnight zone, it will also pursue large prey other than devorators where it encounters them.
To survive in lower-oxygen environments, the Beastbull retains the large ear-shaped gills common in roufos. They can be pressed flat against the body to streamline its shape when pursuing prey, but usually remain erect so that more water can flow through them. The Beastbull has also developed a dorsal fin, which helps make its swimming more effective—when it does come time to swim, it cannot risk wasting energy. Like many abyssal fish on Earth, it can spend some amount of time near the abyssal floor, and it simply swims upwards when it needs more oxygen.
The Beastbull’s reproduction is altered; it has a distinct womb in females and a distinct internal testicle in males, and unborn Beastbulls develop inside keratinous envelopes connected to the womb’s lining. When they are developed enough, they tear out of the envelope and exit their mother on their own. Beastbull larvae are more developed, having adult-like faces from birth, albeit with stubbier tusks. Their limb arrangement is radial for a much shorter amount of time. They still depend on following their parents and feeding on leftovers, and with the new hunting method and with larger prey on the menu, they are less likely to be accidentally left behind. Like its ancestor, the Beastbull mates by pulling back the (albeit small) membrane between its anal fingers and holding hands.