An international team of scientists used synchrotron radiation to image and analyze fossilized fish from the Tanis deposit in North Dakota.
Some 66 million years ago, a catastrophic event wiped out three-quarters of all plant and animal species on Earth, most notably taking down the dinosaurs. The puzzle of why so many species perished while others survived has long intrigued scientists.
A new paper published in the journal Nature concludes that one reason for this evolutionary selectivity is the timing of the impact. Based on their analysis of fossilized fish killed immediately after the impact, the authors have determined that the extinction event occurred in the spring—at least in the Northern Hemisphere—interrupting the annual reproductive cycles of…