By Sid Perkins
Pound-for-pound, an ancient relative of today's piranhas had a stronger bite than gators, sharks, and even the mighty Tyrannosaurus rex. That's the conclusion of field studies carried out on the black piranha (Serrasalmus rhombeus), the largest living species in the carnivorous clan (skeleton). The largest of the 15 fish tested, a 1.1-kilogram specimen measuring almost 37 centimeters long, clamped down on researchers' test equipment with a force almost 30 times its own weight—a ratio unmatched among vertebrates, researchers reveal online today in Scientific Reports. Extrapolating 10 million years back, the team estimates that the jaw-tip bite force of the black piranha's extinct relative—Megapiranha paranensis, which might have reached lengths of about 1.3 meters and weighed up to 73 kilograms—could have been as high as 484 kilograms. Previous studies have calculated the bite force of T. rex to be almost three times that of Megapiranha, but it's important to note, the researchers say, that T. rex was more than 100 times heftier. Not only were Megapiranha's teeth fringed with tiny serrations, unlike the teeth of their modern-day kin, but they also had stout circular roots—a combination that rendered them sharp enough to slice flesh yet sturdy enough to crush the shells of turtles and pierce the armor plates of catfish that lived in the same ecosystem.