Tyrannosaurus rex was far from a plodding Cretaceous era scavenger whose long tail only served to counterbalance the up-front weight of its freakishly big head.
Piranha have tightly packed, interlocking teeth built for rapid puncture and shearing. Piranhas have a voracious appetite for meat, but prefer to scavenge on animals that are already dead.
Tyrannosaurus rex was far from a plodding Cretaceous era scavenger. Its long tail, besides serving to counterbalance the weight of its large head, was also key to its speed.