A good day to die: Doom for the dinosaurs came in springtime

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 at North Dakota's southwestern corner. Scientists said on Wednesday well-preserved fish fossils unearthed at the site are providing a deeper understanding of one of the worst days in the history of life on Earth and shedding light on the global calamity triggered by an asteroid 7.5 miles wide striking Mexico's Yucatan Peninsula. The researchers determined that it was springtime at the fossil site called the Tanis deposit - and throughout the northern hemisphere, including the spot where the asteroid hit - based on sophisticated examinations of bones from three paddlefishes and three sturgeons that died within about 30 minutes of the impact that occurred 2,200 miles away. "Every living thing in Tanis on that day saw nothing coming and was killed almost instantaneously," said Melanie During, a paleontology doctoral student at Uppsala University in Sweden and lead author of the research published in the journal Nature. These waves, carrying immense amounts of sediment and debris, inundated the Tanis site within approximately 15 to 30 minutes after the impact, burying alive all the inhabitants, including the fish whose fossils were studied.