LAUSR

Terrestrial record of recovery The extinction that occurred at the end of the Cretaceous period is best known as the end of the nonavian dinosaurs. In theory, this paved the way for the expansion of mammals as well as other taxa, including plants. However, there are very few direct records of loss and recovery of biotic diversity across this event. Lyson et al. describe a new record from the Cretaceous-Paleogene in Colorado that includes unusually complete vertebrate and plant fossils that describe this event in detail, including the recovery and expansion of mammalian body size and increasing plant and animal biotic diversity within the first million years. Science, this issue p. 977 The terrestrial record of Cretaceous–Paleogene extinction reveals animal and plant recovery and expansion. We report a time-calibrated stratigraphic section in Colorado that contains unusually complete fossils of mammals, reptiles, and plants and elucidates the drivers and tempo of biotic recovery during the poorly known first million years after the Cretaceous–Paleogene mass extinction (KPgE). Within ~100 thousand years (ka) post-KPgE, mammalian taxonomic richness doubled, and maximum mammalian body mass increased to near pre-KPgE levels. A threefold increase in maximum mammalian body mass and dietary niche specialization occurred at ~300 ka post-KPgE, concomitant with increased megafloral standing species richness. The appearance of additional large mammals occurred by ~700 ka post-KPgE, coincident with the first appearance of Leguminosae (the bean family). These concurrent plant and mammal originations and body-mass shifts coincide with warming intervals, suggesting that climate influenced post-KPgE biotic recovery.