Sauropods were long thought to have fallen into rapid decline at the end of the Jurassic period, around 145 million years ago—pushed to the evolutionary sidelines by new and improved herbivorous dinosaurs. Recent discoveries have overturned that scenario, however, by showing that sauropods flourished for another 80 million years, throughout the Cretaceous period—right up until the extinction event that brought the age of dinosaurs to a close. These later sauropods held their own against the newcomers—including the duckbilled and horned dinosaurs—when it came to competing for an important new food source that debuted during the Cretaceous: flowering plants.
from Scientific American