deinosuchus fossil

Daderot/Wikimedia Commons/CC0


The "deino" in Deinosuchus derives from the same root as the "dino" in dinosaur, connoting "fearsome" or "terrible." In this case, the description is apt: Deinosuchus was one of the largest prehistoric crocodiles that ever lived, attaining lengths of up to 33 feet from head to tail and weights in the neighborhood of five to 10 tons.

In fact, for years this late Cretaceous reptile was thought to be the largest crocodile that ever lived until the discovery of the truly monstrous Sarcosuchus (40 feet long and up to 15 tons) relegated it to second place. (Like their modern descendants, prehistoric crocodiles were constantly growing--in the case of Deinosuchus, at the rate of about one foot per year--so it's difficult to know exactly how long the longest-lived specimens were, or at what point in their life cycles they reached maximum size.)

Quick Facts

  • Name: Deinosuchus (Greek for "terrible crocodile"); pronounced DIE-no-SOO-kuss
  • Habitat: Rivers of North America
  • Historical period: Late Cretaceous (80-70 million years ago)
  • Size and weight: Up to 33 feet long and 5-10 tons
  • Diet: Fish, shellfish, carrion and land creatures, including dinosaurs
  • Distinguishing characteristics: Long body with six-foot-long skull; tough, knobby armor


Amazingly, the preserved fossils of two contemporaneous North American tyrannosaurs--Appalachiosaurus and Albertosaurus--bear clear evidence of Deinosuchus bite marks. It's not clear if these individuals succumbed to the attacks, or went on to scavenge for another day after their wounds healed, but you have to admit that a 30-foot long crocodile lunging at a 30-foot long tyrannosaur makes for a compelling picture! This would not, incidentally, have been the only known dinosaur vs. crocodile cage match. (If it did in fact prey on dinosaurs on a regular basis, that would go a long way toward explaining the exceptionally large size of Deinosuchus, as well as the enormous force of its bite: about 10,000 to 15,000 pounds per square inch, well within Tyrannosaurus Rex territory.)

Like many other animals of the Mesozoic Era, Deinosuchus has a complicated fossil history. A pair of this crocodile's teeth were discovered in North Carolina in 1858 and attributed to the obscure genus Polyptychodon, which was itself later recognized as a marine reptile rather than an ancestral crocodile. No less an authority than the American paleontologist Edward Drinker Cope attributed another Deinosuchus tooth discovered in North Carolina to the new genus Polydectes, and a later specimen discovered in Montana was attributed to the armored dinosaur Euoplocephalus. It wasn't until 1904 that William Jacob Holland re-examined all of the available fossil evidence and erected the genus Deinosuchus, and even after that additional Deinosuchus remains were assigned to the now-discarded genus Phobosuchus.

Crocodilian Line of Evolution

Other than its enormous proportions, Deinosuchus was remarkably similar to modern crocodiles--an indication of how little the crocodilian line of evolution has changed over the past 100 million years. For many people, this raises the question of why crocodiles managed to survive the K/T Extinction Event 65 million years ago, while their dinosaur and pterosaur cousins all went kaput. (It's a little-known fact that crocodiles, dinosaurs, and pterosaurs all evolved from the same family of reptiles, the archosaurs, during the middle Triassic period).

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Strauss, Bob. "Deinosuchus." ThoughtCo, Aug. 28, 2020, Strauss, Bob. (2020, August 28). Deinosuchus. Retrieved from Strauss, Bob. "Deinosuchus." ThoughtCo. (accessed June 6, 2023).