What major event likely facilitated the rapid diversification of the Waimanu lineage?

Answer

The extinction of non-avian dinosaurs

The extinction of non-avian dinosaurs at the Cretaceous-Paleogene boundary eliminated many large predators from the ecosystem. This created a vacant ecological landscape, allowing various groups of birds, including the ancestors of penguins, to rapidly adapt and diversify into new niches. This rapid expansion permitted the Waimanu lineage to thrive in the early Paleocene.

What major event likely facilitated the rapid diversification of the Waimanu lineage?
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