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The reptile, which researchers are calling Shieldcroc, lived about 95 million years ago, during the Cretaceous period. A partial specimen suggests its skull was five feet long, said Casey M. Holliday, a paleontologist at the University of Missouri who led the study. “An animal with a head that big,” he said, “is looking at a body 25 to 35 feet.” Today’s crocodiles are much smaller, seldom exceeding 20 feet. Blood-vessel scars on the fossilized skull suggest the presence of a large shield on the crocodile’s forehead. “It was a thickened skull spot, to signal to mates or target adversaries,” Dr. Holliday said. The findings, by Dr. Holliday and Nick Gardner, an undergraduate at Marshall University, in Huntington, W. Va., are reported in the journal PLoS One. The fossil was originally uncovered in Morocco, and then sold to the Royal Ontario Museum in Toronto, where the skull will be put on display this year. Shieldcroc is the earliest African ancestor of the modern crocodile, Dr. Holliday said. During the Cretaceous, many more species of crocodiles existed than do today, he said, adding that discovering ancient species may help explain why some went extinct while others survived. “We’re finding that not only were crocodiles living in the water, but they were living on land and not only chasing animals, but also eating plants,” Dr. Holliday said. “Crocodiles were operating a whole suite of niches that they don’t know today.”
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