New Dinosaur Extinction Event Details Uncovered In North Dakota

Along with the profusion of dinosaurs, mollusks, and reptiles fossilized after the catastrophe, scores of fishes and vegetation were also washed up and instantly captured in the deposits. Researchers have now discovered (via Live Science) that the entire event happened within 30 minutes of the asteroid striking the Earth. Along with this synopsis about the timing of the event, researchers have discovered clues about the season in the fishes.

Researchers found the acipenseriforms that were abundant at the time, including paddlefishes and sturgeons, were buried alive under the rubble. Skeletal elements from three sturgeons’ pectoral fin spines and three paddlefish jawbones recovered from the site were studied to see the growth in bones of these fishes. These growth patterns identified using the bone cell density led to findings of the seasonal availability of food, which helped the researchers identify the season in which the K-T extinction event took place.

Using synchrotron X-ray, the researchers reconstructed the fossils in 3D. As fishes age, they undergo an addition of layers to their bones and this growth peaks around the end of summer and the beginning of winter. Researchers found the fishes in consideration had just entered the period of notable bone growth, and that coincided with spring.