Crocodilians and Sphenosuchians
Modern crocodilians have sprawling limbs and broad bodies, giving them a distinctive side-to-side swagger when walking on land.
The sphenosuchians, in contrast, had an erect stance, like dinosaurs and mammals.
In water, crocodilians tuck their limbs into their bodies and swish their powerful tails back and forth to swim. Nostrils located on the top of their snouts allow them to breathe while keeping their bodies submerged.
Opportunistic feeders, crocodilians lie in wait for prey to cross their paths and then lunge with lightninglike speed to capture it between their powerful jaws. Once they impale it with their sharp teeth, crocodilians swallow prey whole.
According to Sues, nobody knows what factors led modern crocodilians to adapt a semiaquatic lifestyle, but, he said, "The ability to crush prey with their jaws was already well established in far more remote ancestors of crocodilians [than Junggarsuchus]."
Found in Xinjiang, China, the Junggarsuchus fossil comprises the front half of the skeleton and is the most complete known skeleton of a nonmarine crocodilian ancestor.
The fossil dates to the Middle Jurassic period, about 175 million years ago. "This part of Asia, which is the land area most removed from any seacoast in the world, was beginning its long history of seasonal aridity then," Clark said.
Conifer and palmlike cycad trees and ferns dominated the landscape. There were no flowering plants.
Several rivers flowed from the mountains, and floods spreading out from stream channels trapped many of the fossils that researchers find today, Clark said.
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