Paleontologists have determined that Purussaurus brasiliensis, a massive caiman that lived in South America during the Late Miocene, evolved the strongest bite of any four-limbed animal. At 15,500 pounds of force, its bite was twice as powerful as the T-rex's.

Top illustration: Tito Neto

This crocodylian was truly a monster. Adults could reach as long as 41 feet (12.5 meters) in length and weigh upwards of 18,100 pounds (8,210 kg). To survive, it had to consume 88 pounds (40 kg) of food each day — and it used its unusually powerful jaws to get the job done in the ancient pan-Amazonian wetlands in which it prowled.

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A new analysis by Tito Aureliano and colleagues shows that Purussaurus was capable of generating a bite force of 69,000 newtons (N), or 15,512 pounds of force. That's 20 times the strength of a white shark's bite, and twice as strong as T. rex's. This establishes a new upper bound of bite forces among all tetrapods, past or present.

Image: Purussaurus brasiliensis skull anatomy (left) and a tooth sample (right). (Tito Aureliano et al/PLOS)

"The extreme size and strength reached by this animal seems to have allowed it to include a wide range of prey in its diet, making it a top predator in its ecosystem," write the authors in the study. "As an adult, it would have preyed upon large to very large vertebrates, and, being unmatched by any other carnivore, it avoided competition."

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The researchers theorize that the extreme size and power of Purussaurus was an adaptive response to intense competition.

At the same time, however, the creature's large body size may have been its undoing. As noted by the researchers, "The constantly changing environment on a large geological scale may have reduced its long-term survival, favoring smaller species more resilient to ecological shifts."

Read the entire study at PLoS: "Morphometry, Bite-Force, and Paleobiology of the Late Miocene Caiman Purussaurus brasiliensis."