An artistic construction shows a seiche wave surging into the Tanis river, bringing in fishes and everything in its path while impact spherules rain down from the sky on the day of the deadly asteroid impact in modern-day Mexico. (Joschua Knüppe)

On a spring day 66 million years ago, paddlefish and sturgeon swam in a river that meandered through a flourishing landscape populated by mighty dinosaurs and small mammals in North Dakota’s southwestern corner.

Death came from above that day.

Scientists said on Wednesday that well-preserved fish fossils unearthed at the site are providing a deeper understanding of one of