Final answer:
The conflicting patterns in Maastrichtian dinosaurs are partly due to the mass extinction at the Cretaceous-Paleogene boundaries, causing a significant loss of diversity and total number of organisms, influenced by an asteroid impact and volcanic activity.
Step-by-step explanation:
The two conflicting patterns seen in the Maastrichtian dinosaurs of western North America result, in part, from the mass extinction that took place at the Cretaceous-Paleogene boundaries. This extinction event led to a loss of diversity, marked by fewer shapes of pollen grains, and reduced the total number of organisms. The extinction coincided with the impact of a large asteroid and may have also prompted massive volcanic eruptions that altered global plant life, climate, and ocean chemistry. These radical environmental changes directly affected dinosaur populations and their ecosystems, leading to the end of the Mesozoic era and the extinction of the dinosaurs, with the exception of avian dinosaurs which evolved into modern birds.
In addition to asteroid impact, the end of the Triassic period also marked significant species loss, potentially attributable to increased atmospheric CO₂ from volcanic activity. This underscores how catastrophic events have shaped the distribution and abundance of life throughout Earth's history. Archaeopteryx fossils provide support for evolutionary theory, indicating a common ancestor due to shared reptilian and avian traits.