Were Dinosaurs in Decline Before Mass Extinction?
Despite years of intensive research about the extinction of non-avian dinosaurs about 65.5 million years ago, a fundamental question remains: were dinosaurs already undergoing a long-term decline before an asteroid hit at the end of the Cretaceous? A study led by scientists at the American Museum of Natural History gives a multifaceted answer.
The findings, published in Nature Communications, suggest that in general, large-bodied, “bulk-feeding” herbivores were declining during the last 12 million years of the Cretaceous. But carnivorous dinosaurs and mid-sized herbivores were not. In some cases, geographic location might have been a factor in the animals’ biological success. The research team is the first to look at dinosaur extinction based on “morphological disparity”—the variability of body structure within particular groups of dinosaurs.