A reptile to reckon with.

Imagine a crocodile bigger than a station wagon. How about three station wagons placed end to end? That's about the size of a beast that terrorized the Amazon region more than 8 million years ago, suggest Carl D. Frailey of Johnson County Community College in Overland Park, Kan., and Kenneth E. Campbell of the Natural History Museum of Los Angeles County.

While excavating along the border between Peru and Brazil in 1989, a crew led by Frailey found a startlingly large crocodilian skull of the genus Purussaurus. Last year, the scientists finished removing sedimentary deposits from that skull and a jowbone from the same genus. Frailey and Campbell now estimate that the giant crocodilian stretched 12 meters (39 feet) in length and stood 2.6 meters (8 feet) tall. Purussaurus may have weighed 10,000 to 12,000 kilograms, which would have made it even more massive than Tyrannosaurus rex, often touted as the largest terrestrial carnivore.

Frailey and Campbell note that even larger members of the Purussaurus genus must have existed, because a museum in Brazil has a jawbone 30 centimeters longer than the one they found. The Brazilian jawbone may have belonged to an animal as long as 13 to 14 meters, they say.

What would such a behemoth have eaten? Campbell thinks the toothy carnivore could have dined on birds, large turtles or rodents. These were no ordinary 20th-century mice, however. At that time, says Campbell, rodents could have reached the size of small cattle.