The Cretaceous–Paleogene (K–Pg) extinction event (also known as the Cretaceous–Tertiary (K–T) extinction) was a sudden mass extinction of three-quarters of the plant and animal species on Earth, approximately 66 million years ago.
A, the others are unrealistic speeds.
Mesozoic, the era contained both large reptiles and small birds/mammals. It's interesting, coming from an evolutionary biology.
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