A sample of the morphological diversity seen in Mesozoic crocodiles, with the lower jaws highlighted in anatomical position. From top to bottom, the animals are Goniopholis (Jurassic to Cretaceous), Simosuchus (Cretaceous), Dakosaurus (Jurassic to Cretaceous), Cricosaurus (Jurassic to Cretaceous) and Mariliasuchus (Cretaceous). The silhouettes are not to scale.
Ancient crocodilians once evolved lifestyles unlike anything seen today in their modern relatives, including plant-eating herbivores, small insect-eating runners, marine fish eaters and giant carnivores on both land and in the sea. There were even crocs whose feeding mimicked that of modern killer whales.
Now, researchers have uncovered details on how this extraordinary diversity evolved so ancient crocodilians could survive in a world dominated by dinosaurs.
While modern crocodiles mostly live in freshwater habitats and feed on mammals and fish, during the Mesozoic Era (about 250 million to 65 million years ago) — the era often called the Age of Reptiles — a "lost world" of dazzling crocodilian variety existed. [Image Gallery: Ancient Monsters of the Sea]
For the rest of the story: http://www.livescience.com/39551-how-crocs-survived-dinosaur-dominated-world.html