P1.129 Wednesday, Jan. 4 Why dinosaurs went extinct: A species-centered analysis PIRTLE, Elia/I*; TRACY, C/Richard; University of Nevada Reno; University of Nevada Reno email@example.com
The mass extinction at the end of the Cretaceous, 65 Ma, resulted in the loss of all non-avian dinosaurs. Our species-level analysis of 555 dinosaur species reveal a gradual decline in species richness throughout the last two ages of the Cretaceous, which is a pattern inconsistent with the “asteroid impact” hypothesis as the leading cause of dinosaur extinction. A more likely explanation for the late Cretaceous dinosaur extinctions is that large-bodied species of dinosaurs, which were confined to small habitat fragments, went extinct due to stochastic population dynamics (or Gambler’s Ruin) exacerbated by top-down control by ferocious predators. Similar extinctions of large-bodied dinosaurs occurred three times during the Mesozoic followed by re-radiations of dinosaur species after each extinction event. In the final Cretaceous extinction, occurring 6-19 million years before the K/T boundary, the surviving small-bodied dinosaur species were the ancestors of modern birds.