Final answer:
The selectivity of the terminal Cretaceous extinction is a valid topic for explanation, based on evidence such as a significant iridium anomaly, impact crater, and changes in the fossil record including the reduction of biodiversity indicated by pollen grain diversity.
Step-by-step explanation:
The claim that the selectivity of the terminal Cretaceous extinction merits an explanation is indeed true. The Cretaceous-Paleogene (K-Pg) mass extinction event is one of the most well-documented and studied mass extinctions, and it occurred approximately 65 million years ago. This catastrophic event led to the disappearance of the dinosaurs (except for a theropod clade that evolved into birds) and affected many other species, with every land animal weighing more than 25 kg becoming extinct.
Scientists propose that the primary cause for this extinction was the impact of a large meteorite off the coast of what is now the Yucatán Peninsula, supported by high levels of iridium found at the boundary layer between the Cretaceous and Paleogene periods in the geological record. This iridium anomaly points to an influx from space, as iridium is rare on Earth's crust but common in asteroids. An impact crater corresponding to the estimated time of the extinction provides further evidence for this hypothesis.
Recovery from the K-Pg mass extinction was relatively quicker in geological terms, taking about 10 million years. The extinction event led to a reduction in biodiversity, as evidenced by a decrease in the number and variety of pollen grains found in geological strata from the period.