Final answer:
The last interval of Cretaceous time is the Maastrichtian. It marks the end of the Mesozoic Era, which includes the Cretaceous-Paleogene extinction event that led to the demise of the dinosaurs.
Step-by-step explanation:
The last interval of Cretaceous time is the Maastrichtian. The Cretaceous period is a significant geological era that lasted from about 145 to 66 million years ago, marking the end of the Mesozoic Era. During this time, it was the dinosaurs that dominated the landscape, a period often referred to as the 'Age of Reptiles'. The Cretaceous period is followed by the Tertiary period. An important event marking the transition between these periods is the Cretaceous-Paleogene (K-Pg) extinction event, which led to the demise of the dinosaurs and many other forms of life approximately 66 million years ago.