Late Cretaceous

The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. This time period was very important for understanding Earth's history because many kinds of animals and plants lived and changed during this time.

Rock layers from the Late Cretaceous are called the Upper Cretaceous Series. The name Cretaceous comes from the word creta, a Latin word for white limestone known as chalk. Some famous chalk cliffs, like those in northern France and the white cliffs of south-eastern England, were formed during this period. Studying the Late Cretaceous helps us learn about the world long before humans existed.

Climate

See also: Cretaceous Thermal Maximum

During the Late Cretaceous, the Earth had a warmer climate than today. However, it was slowly getting cooler over time. The very warm areas, called the tropics, were found only near the equator, and places farther north started to have more noticeable seasons.

Geography

Because of how Earth's plates moved, the Americas slowly moved west, making the Atlantic Ocean bigger. The Western Interior Seaway split North America into two parts: Appalachia and Laramidia. India kept moving north toward Asia. In the Southern Hemisphere, Australia and Antarctica stayed connected but started moving away from Africa and South America. Europe was made up of many islands, and some of these islands had special small dwarf dinosaur species.

Vertebrate fauna

In the Late Cretaceous, many kinds of dinosaurs lived in different parts of the world. In places like western North America and eastern Asia, hadrosaurs, ankylosaurs, and ceratopsians were common. Large predators called tyrannosaurs were top hunters in North America, while smaller ones lived in Asia. Other dinosaurs like pachycephalosaurs and dromaeosaurids were also found in both areas. In a region called Gondwana, different dinosaurs lived, including abelisaurids and titanosaurs.

Birds were becoming more common too, evolving into many different shapes and sizes. Some could fly, while others, like marine Hesperornithes, lost the ability to fly and lived in the ocean. Pterosaurs, flying reptiles, were still around but not as common as birds. Mammals were small but lived in many ways, eating different foods and moving in unique styles. In the oceans, new large sea reptiles like mosasaurs appeared, along with sharks and different kinds of plesiosaurs. Some older sea reptiles, like ichthyosaurs, were no longer around.

Flora

Near the end of the Cretaceous Period, flowering plants became more common. In cooler areas, we could find many plants we recognize today, like magnolias, sassafras, and roses.

Cretaceous–Paleogene mass extinction discovery

Main article: Cretaceous–Paleogene extinction event

The Cretaceous–Paleogene extinction event was a big event that happened about 66 million years ago. Many animals and plants disappeared quickly during this time. This event ended the time known as the Mesozoic Era and started the Cenozoic Era.

Scientists think this event might have been caused by a huge space rock hitting Earth and lots of volcanoes erupting. These events changed the world and made it hard for many living things to survive.