11 Of Ancient Earth’s Most Unbelievable Prehistoric Animals

Published December 2, 2021
Updated February 7, 2025

Deinosuchus: The Fearsome Prehistoric Animal Called ‘Terrible Crocodile’

Deinosuchus

Wikimedia CommonsThe stunning skull of a Deinosuchus rugosus.

When it comes to prehistoric animals that seem like modern-day monsters, it’s hard to beat Deinosuchus. Stretching 33 feet long and with teeth the size of bananas, Deinosuchus terrified North America during the late Cretaceous period, some 82 to 73 million years ago. Even its name literally translates to “terrible crocodile.”

The giant crocs mostly ate sea turtles and shellfish, but sometimes tangled with T. Rex cousins like Appalachiosaurus montgomeriensis and Albertosaurus — and left the bite marks to prove it.

Deinosuchus was a giant that must have terrorized dinosaurs that came to the water’s edge to drink,” explained Adam Cossette, a vertebrate paleontologist at the New York Institute of Technology who has studied the beasts.

These fearsome prehistoric animals lived across the present-day United States and Mexico. Fossils have been found in Utah, Montana, Wyoming, New Mexico, New Jersey, Georgia, Alabama, Mississippi, Texas, and North Carolina.

The monster does differ somewhat from modern-day crocodiles, however. In addition to its massive size, it also has a bulb-like snout with two vents. Scientists aren’t sure what Deinosuchus needed the vents for, but they possibly helped cool the animals down.

As with other prehistoric animals on this list, it took scientists a while to understand the full picture of these ancient animals. Deinosuchus fossils were originally classified under the genus Polyptychodon, another marine predator, but in 1904, the zoologist and paleontologist William Jacob Holland studied the available evidence and concluded that Deinosuchus was a monster all its own.

Specimens of Deinosuchus, Cossette noted, were few and far between. But the ones that scientists have found are “HUGE.”

For a long time, Deinosuchus was considered the largest crocodile ever discovered. It’s since been dethroned by Sarcosuchus imperator who, at 40 feet long and 17,600 pounds, could have taken Deinosuchus in a fight.

author
Kaleena Fraga
author
A senior staff writer for All That's Interesting since 2021 and co-host of the History Uncovered Podcast, Kaleena Fraga graduated with a dual degree in American History and French Language and Literature from Oberlin College. She previously ran the presidential history blog History First, and has had work published in The Washington Post, Gastro Obscura, and elsewhere. She has published more than 1,200 pieces on topics including history and archaeology. She is based in Brooklyn, New York.
editor
Leah Silverman
editor
A former associate editor for All That's Interesting, Leah Silverman holds a Master's in Fine Arts from Columbia University's Creative Writing Program and her work has appeared in Catapult, Town & Country, Women's Health, and Publishers Weekly.
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Fraga, Kaleena. "11 Of Ancient Earth’s Most Unbelievable Prehistoric Animals." AllThatsInteresting.com, December 2, 2021, https://allthatsinteresting.com/prehistoric-animals. Accessed July 27, 2025.