Final answer:
The statement regarding the overstating of the terminal Cretaceous extinction's magnitude is false. The Cretaceous-Paleogene extinction is well-supported by evidence like iridium levels and impact craters, and led to a major reduction in biodiversity and organisms.
Step-by-step explanation:
The statement 'Current estimates may greatly overstate the magnitude of the terminal Cretaceous extinction' is false. The magnitude of the Cretaceous-Paleogene (K-Pg) mass extinction is well-supported by scientific evidence. It is one of the five mass extinctions preserved in the fossil record, known for the disappearance of the dinosaurs (except for a theropod clade that gave rise to birds) roughly 65 million years ago. Geological evidence, including a spike in iridium levels and the discovery of a large impact crater, support the hypothesis that this extinction was caused by the impact of a large meteorite. The K-Pg extinction event resulted in a significant loss of biodiversity, indicated by the reduction of different types of pollen grains and a decrease in the number of organisms.