Evolution: The end of the dinosaur era pinpointed in spring
A paper suggesting that the collision of the Chicxulub asteroid, which ended the Mesozoic era of dinosaurs, occurred in the spring of the Northern Hemisphere is published in Nature.Our findings help explain the patterns of extinction that followed and provide a better understanding of this crucial moment in Earth's history.
Approximately 6600 million years ago, a mass extinction event occurred in which a large asteroid collided with the current Yucatan Peninsula in Mexico, killing 76% of all species (including non-bird-type dinosaurs, winged dragons, and ammonites). Happened.Previous studies investigating the timing of this event have focused on the 1000-year timescale, so it is not known in which season the asteroids collided.To solve this problem, Melanie During and colleagues examined the remains of filter feeders (sturgeon and paddlefish) that died in large numbers on the day of the asteroid collision.The fossil bones of these fish were well preserved, and a unique three-dimensional growth pattern was observed inside them, and a record of seasonal changes was obtained.This observation, when combined with carbon isotope data, suggests that these fish died in the spring of the Northern Hemisphere.
The remains of these filter feeders were found in the Late Cretaceous sediments of North Dakota, USA.The gills of these fish were clogged with debris from asteroid collisions, but were not found in the digestive system downstream.This suggests that the static vibrations caused by the collision of asteroids (the vibration of the water surface such as lakes and marshes) caused the rivers to suddenly flood and these fish died almost instantly.This catastrophic impact is thought to coincide with a period of particular susceptibility to many Northern Hemisphere species that bred in the spring and left offspring. During and colleagues point out that celestial impacts occurred in the Southern Hemisphere in the fall, and their recovery is thought to have reached up to twice as fast as in the Northern Hemisphere.
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* This article is reprinted from "Nature Japan Featured Highlights".
Reprinted from: "Evolution: The dinosaur era ended in spring in the Northern Hemisphere'
