Name means: Terrible Crocodilian


Species: rugosus, riograndensis

Range: Late Cretaceous (Campanian, 84-73 MYA) from the United States and Mexico, including Texas, Utah, Montana, Georgia, Arkansas, New Jersey

Size estimate: 35-40 ft length, 6-8 tons

Discovery: William J. Holland, 1909

Classification: eureptilia, archosauria, pseudosuchia, crocodilia, alligatoroidea


Deinosuchus may have been the largest alligator ever to haunt the swamps of North America. Experiments with its bones show that it grew at the same rate as modern alligators, but stayed in its period of high growth for a longer time. Since alligator anatomy has changed little since the Jurassic, Deinosuchus may have behaved like them in other ways as well. Despite their resemblance, however, modern alligators do not descend from Deinosuchus.

Like modern alligators, it probably ate different prey depending on where it lived. It may have eaten large fish and sea turtles near the coast. Further inland it might have ambushed large dinosaurs. During much of the Cretaceous a long seaway split North America, and Deinosuchus lived in both sides. This may have caused two species of Deinosuchus to develop. The smaller size of the eastern type, Deinosuchus rugosus, may hint at a more varied diet like that of modern alligators. Deinosuchus riograndensis ruled the western half. Scientists originally called it “Phobosuchus” or “Fear Crocodilian” because of its size. It may have preferred a diet of large dinosaurs.