The extinction of the dinosaurs in North America
David E. Fastovsky, Department of Geosciences, University of Rhode Island, and Peter M. Sheehan, Department of Geology, Milwaukee Public Museum.
Did the dinosaurs really go abruptly extinct 65 million years ago at the Cretaceous-Tertiary ("K-T") time boundary, or was their K-T extinction the end result of a gradual decline over millions of years? The imperfect record available from scarce dinosaur remains has made this question a true enigma and the source of a long-standing and contentious debate. David E. Fastovsky and Peter M. Sheehan conclude, after a careful review of the fossil record from the best-documented dinosaur sites (in North America), that the extinction was indeed geologically instantaneous. The authors argue that the sudden die-off was different in scope from previous fluctuations in dinosaur diversity through the dinosaurs' 160 million years on Earth. The authors consider the dinosaurs to have been direct casualties of the K-T impact of an asteroid with Earth and review several potential explanations for the mechanism of the extinction. All of these are concordant with the asteroid with Earth and review several potential explanations for the mechanism of the extinction. All of these are concordant with the asteroid impact as the ultimate cause.