Biosphere: Dante’s Inferno
Umm, okay, what the hell is that? That's just... all kinds of wrong. Cerberus dates back to Greek mythology, where he was the guardian of the gates of Hades. In the original poem of Dante's Inferno, he is seen on the circle of Hell dealing with gluttons, sitting atop a writhing pile of souls as frozen offal and feces rain down from the sky. There he tears at and eats the sinners.
But this thing... Cerberus is supposed to be a dog, right? This thing looks like a dental accident. Anyway, where were we?
Ah yes, Canus threeheadicus, surely an apex predator, considering its massive girth. Noting the distinct lack of canines in its teeth, the likely conclusion would initially point to herbivorous behavior, but field observations have confirmed an omnivorous appetite. With prehensile, extendable necks, hunting patterns would likely follow an ambush approach, with Cerberus lying in wait, motionless until prey wanders near, much like the feeding pattern of the alligator snapping turtle.
The rather moist, porous-looking membrane that serves as its skin suggest an amphibious nature as well. Like many aquatic predators, Cerberus probably waits beneath the water (or in the case of its particular environment, stagnant pools of feces), with necks extended upward, allowing just its eyes to breach the surface. Also note that the body exhibits mimic traits, although how mimicking what appears to be a giant, dead human head would be useful remains a mystery. It's possible that within its environment there are even larger predators that hunt giant humans, in which case retracting its neck-stalks and playing dead could prove invaluable to its survival.