New details about dinosaur extinction event discovered in North Dakota
Along with the profusion of fossilized dinosaurs, molluscs and reptiles after the disaster, dozens of fish and vegetation were also discarded and instantly captured in the deposits. Researchers have now discovered (via Live Science) that the whole event happened within 30 minutes of the asteroid’s impact on Earth. Along with this synopsis of the timing of the event, the researchers uncovered clues about the season in fish.
The researchers found that the acipenseriformes that were abundant at the time, including paddlefish and sturgeon, were buried alive under the rubble. Skeletal elements from the spines of the pectoral fins of three sturgeons and the jaws of three paddlefish recovered from the site were studied to see the bone growth of these fish. These growth patterns identified using bone cell density led to insights into seasonal food availability, which helped researchers identify the season in which the KT extinction event took place.
Using synchrotron X-rays, the researchers reconstructed the fossils in 3D. As fish age they experience an addition of layers to their bones and this growth peaks towards the end of summer and the beginning of winter. The researchers found that the fish in question had just entered the period of noticeable bone growth, and this coincided with spring.