A “terror crocodile” the length of a London bus had teeth the size of bananas and outweighed even the largest predatory dinosaurs.
The enormous reptile had the head size and crushing jaw strength to prey on and eat dinosaurs, according to research published in the Journal of Vertebrate Paleontology.
“Deinosuchus was a giant that must have terrorised dinosaurs that came to the water's edge to drink,” said Dr Adam Cossette of Arkansas State University.
“Until now, the complete animal was unknown.
“These new specimens we've examined reveal a bizarre, monstrous predator with teeth the size of bananas.”
The creature was 33ft long – just short of the length of a London Routemaster bus.
Co-author Stephanie Drumheller-Horton, a paleontologist at the University of Tennessee, added: “Deinosuchus seems to have been an opportunistic predator, and given that it was so enormous, almost everything in its habitat was on the menu.
“We actually have multiple examples of bite marks made by D. riograndensis and a species newly described in this study, D. schwimmeri, on turtle shells and dinosaur bones.”
In spite of the genus's name, which means “terror crocodile”, Deinosuchuas are actually more closely related to alligators.
But based on measurements of its skull, it looked like neither an alligator nor a crocodile – with a nose that was inflated at the front unlike either.
The reason for its enlarged nose is unknown.
“It had two large holes are present at the tip of the snout in front of the nose,” Cossette said.
“These holes are unique to Deinosuchus and we do not know what they were for, further research down the line will hopefully help us unpick this mystery and we can learn further about this incredible creature.”
It is thought to have been among the largest “crocodylians” ever to live, with two species called Deinosuchus hatcheri and Deinosuchus riograndensis living in the west of America, ranging from Montana to northern Mexico.
Another, Deinosuchus schwimmeri, lived along the Atlantic coastal plain from New Jersey to Mississippi.
"It was a strange animal," says Brochu. "It shows that crocodylians are not 'living fossils' that haven't changed since the age of dinosaurs. They've evolved just as dynamically as any other group."
Deinosuchus disappeared before the main mass extinction at the end of the age of dinosaurs (Meozoic). The reason for its extinction remains unknown.