NEW YORK (NYTIMES) - They had teeth the size of bananas, were as long as buses and limos, and preyed on dinosaurs that fed near their waterways.
Those are among some of the findings presented in a new study announced this week about an enormous ancient animal called the "terror crocodile", or Deinosuchus.
The research, published in the Journal of Vertebrate Paleontology, found that the Deinosuchus, a lineage of the giant crocodilians from North America, grew up to 10.1m long and "was the largest carnivore in its ecosystem" in the late Cretaceous period about 75 million to 82 million years ago.
Dr Adam Cossette, a vertebrate paleobiologist who led the study, said in an e-mail on Tuesday (Aug 11) that while it was difficult to determine their average size because there were so few known specimens, "the specimens that we do have are all huge".
Dr Cossette, of the New York Institute of Technology College of Osteopathic Medicine of Arkansas State University, said that large specimens were 9.1m to 10.6m long and weighed about 3,628kg.
For comparison, he said that a large American alligator today is about 3.6m to 4m long, weighs about 317kg to 362kg, and has teeth about 7.6cm long at the tip of its snout.
He also said that the ancient reptiles had a large enough head and strong enough jaws to prey on dinosaurs that lived among them.
"Deinosuchus was a giant that must have terrorised dinosaurs that came to the water's edge to drink," he said in a statement.
"Until now, the complete animal was unknown. These new specimens we've examined reveal a bizarre, monstrous predator."
In addition to killing dinosaurs, the animals, because of their size, probably preyed on just about anything that wandered their way. Researchers found multiple bite marks on turtle shells and dinosaur bones.
They also found that at least three species of the Deinosuchus roamed what is now the United States and Mexico.
Two species lived in the West, from Montana to northern Mexico, and another species lived along the Atlantic coastal plain, from New Jersey to Mississippi.
The study said that despite the name of the genus, which means "terror crocodile", the creatures were more closely related to alligators. But because of an "enormous skull", they did not look like either crocodiles or alligators.
The snout was long and broad "but inflated at the front around the nose in a way not seen in any other crocodylian, living or extinct", according to the researchers, using an alternate spelling of crocodilian.
The reason for its enlarged nose is unknown, the researchers said.
They also do not know why the animal had two large holes at the tip of its snout, in front of the nose.
"These holes are unique to Deinosuchus," Dr Cossette said. "Further research down the line will hopefully help us unpick this mystery."
His colleague on the study, Dr Christopher Brochu, a vertebrate palaeontologist at the University of Iowa, said that the fossils showed how crocodilians were "not 'living fossils' that haven't changed since the age of dinosaurs".
"They've evolved just as dynamically as any other group," he said in the statement.
"The earliest ancestors of the American alligator, such as Deinosuchus, were bizarre and unlike anything that we see in the modern crocodylian species of today," Dr Cossette said in the e-mail.
"The evolutionary history of Crocodylia is much more fascinating than meets the eye."
Dr Mark A. Norell, curator and chair of the American Museum of Natural History's division of palaeontology, said the study had many new findings, especially about the strange inflation at the end of the skull, the animal's heaviness and size, and the shape of its skull.
And Dr Norell said there was much more to learn because the animals' fossils remained rare, under-collected and understudied.
"Usually, their collection and study is an afterthought," he said, "as most work done on these formations and deposits is dominated by dinosaurs."