By | September 9, 2016

Crocodylomorphs (which means having a crocodile-like shape) were part of the archosaur, or “ruling reptile” group, along with dinosaurs and pterosaurs. Some were small, others gigantic, and they lived both on land and in the sea. Like their modern relatives— crocodiles and alligators—most were active hunters, always ready to ambush passing fish or land animals.


Key features
■ Long bodies
■ Short, strong limbs
■ Powerful jaws
■ Sharp teeth

Crocodylomorphs first appeared 225 million years ago, in the Late Triassic and were the ancestors of modern crocodiles and alligators.

Sphenosuchus (SFEN-oh-soo-kuss)



An image of a Sphenosuchus skull

When: 200 million years ago (Early Jurassic)

Fossil location: S. Africa

Habitat: Land

Length: 3–5 ft (1–1.5 m)

Diet: Small land animals

Sphenosuchus was one of the earlier crocodylomorphs. It had long and slender legs—a sign it could run fast when chasing prey or fleeing from predators. Only a skull and a few leg bones have been found. Air-filled spaces in parts of the skull resemble those found in birds, hinting at an evolutionary link between crocodylomorphs and birds.

Geosaurus (GEE-oh-SORE-us)


When: 165–140 million years ago (Late Jurassic to Early Cretaceous)

Fossil location: Europe, N. America, the Caribbean

Habitat: Oceans

Length: 10 ft (3 m)

Diet: Fish

When scientists first came across fossils of this species they thought it lived on land, and gave it the name Geosaurus, or “earth lizard.” They now know that this animal spent most of its life underwater. Geosaurus had a much longer and narrower snout than most crocodylomorphs. It may also have had a special gland in its mouth, like crocodiles and gharials, to help it remove salt from the water it drank.

Dakosaurus (DACK-oh-SORE-us)


When: 165–140 million years ago (Late Jurassic to Early Cretaceous)

Fossil location: Worldwide

Habitat: Shallow seas

Length: 15 ft (4–5 m)

Diet: Fish, squid, and marine reptiles

Dakosaurus was a fierce marine predator. With a skull like that of a carnivorous dinosaur and large, jagged teeth, it had a powerful bite that could slice through the flesh of other marine reptiles and crunch the shells of ammonites. Its legs had become paddles that helped it steer as its fishlike tail propelled it through the water. It could chase and overcome animals much bigger than itself.

Simosuchus (SIGH-moe-SOO-kuss)


When: 70 million years ago (Late Cretaceous)

Fossil location: Madagascar

Habitat: Forests

Length: 4 ft (1.2 m)

Diet: Plants, maybe some insects

Simosuchus was an unusual crocodylomorph because it had a short skull and blunt face. In fact, its name means “pug-nosed crocodile.” Even more unusually, this reptile’s teeth show that it was probably a vegetarian that occasionally ate insects.

Steneosaurus (STEN-ee-oh-SORE-us)


When: 200–145 million years ago (Early Jurassic to Early Cretaceous)

Fossil location: Europe, Africa

Habitat: Estuaries and coastal waters

Length: 3–13 ft (1–4 m)

Diet: Fish

Steneosaurus was probably an estuary-living crocodylomorph that ventured out onto land to lay its eggs. Although its long body was adapted for swimming, its limbs had not changed into flippers. It had a thin snout full of sharp teeth for eating fish, and its body was heavily armored to protect it against predators.

Deinosuchus (DIE-no-SOO-kuss)


When: 70–65 million years ago (Late Cretaceous)

Fossil location: USA, Mexico

Habitat: Swamps

Length: 33 ft (10 m)

Diet: Fish, medium to large dinosaurs

Deinosuchus was one of the largest prehistoric alligators, nearly five times bigger and heavier than any found today. This alligator may have preyed on dinosaurs as big as itself—fossils of certain tyrannosaurs show Deinosuchus bite marks. It may have hunted by waiting patiently at the water’s edge to pounce on passing fish, marine reptiles, or land animals. Small victims were swallowed whole. Larger prey were ripped apart into bite-sized chunks.



Deinosuchus killed its prey as modern alligators do—by dragging its victims underwater and drowning them.



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