The Cenozoic Era, also known as the "Age of Mammals," is the geological period defined by mammalian dominance. It commenced around 66 million years ago, following the extinction event that eradicated dinosaurs. This era is notable for the evolutionary advancement and widespread distribution of mammals, birds, and angiosperms. The Cenozoic Era is segmented into two primary periods: the Paleogene Period and the Neogene Period. Therefore, the correct designation is Cenozoic Era.