Late Cretaceous refers to the second half of the Cretaceous Period, named after the famous white chalk cliffs of southern England, which date from this time. Rocks deposited during the Late Cretaceous Period are referred to as the Upper Cretaceous Series.
This was a period of great success for dinosaurs, with many new types appearing and diversifying, such as the Tyrannosaurs, duck bills, Ankylosauridae, and horned dinosaurs in Asiamerica (Western North America and eastern Asia), and Titanosaurs and Abelisaurs in Gondwana.
Birds became increasingly common and diverse, replacing the pterosaurs which retreated to increasingly specialised ecological niches.
In the seas, mosasaurs suddenly appeared and underwent a spectacular evolutionary radiation. Modern sharks also appeared and giant-penguin-like polycotylid pliosaurs (3 metres long) and huge long-necked elasmosaurs (13 metres long) also diversified. These predators fed on the numerous teleost fishes, which in turn evolved into new advanced and modern forms (Neoteleostei).
Near the end of the Cretaceous Period, flowering plants diversified and didelphid marsupials and primitive placental mammals also became common.
The late Cretaceous period was divided into 6 sub periods:
Cenomanian - The Cenomanian (also known as Woodbinian) is the first stage of the Late Cretaceous Epoch. It spans the time between 99.6 million years ago and 93.5 million years ago.
Turonian - The Turonian is a stage of the Late Cretaceous Epoch. It spans the time between 93.5 million years ago and 89.3 million years ago.
Coniacian - The Coniacian is a stage of the Late Cretaceous Epoch. It spans the time between 89.3 million years ago and 85.8 million years ago.
Santonian - The Santonian is a stage of the Late Cretaceous Epoch. It spans the time between 85.8 million years ago and 83.5 million years ago.
Campanian - The Campanian is a stage on the geologic time scale occurring from 83.5 million years ago to 70.6 million years ago.
Maastrichtian -The Maastrichtian is the last stage of the Cretaceous period, and therefore of the Mesozoic era. It spanned from 70.6 million years ago to 64.9 million years ago.
At the end of this period, there was a mass extinction commonly referred to as the K/T (or Cretaceous/Tertiary) extinction. At this extinction event, many commonly recognized groups such as dinosaurs, plesiosaurs and mosasaurs, as well as many other lesser known groups, died out. The Maastrichtian is named after the Dutch city Maastricht.
The breakup of the supercontinent Pangaea into separate continents was underway. The separation of Laurasia and Gondwana was complete. In the first half of the Cretaceous, temperatures were warm, seasonality was low, and global sea levels were high (no polar ice!). At the end of the Cretaceous, there were severe climate changes, lowered sea levels, and high volcanic activity.
The Cretaceous period ended 65 million years ago with the extinction of the dinosaurs and many, many other prehistoric life forms. This mass extinction was the second-most extensive in the history of the Earth.
Years of volcanic eruptions produced massive waste landscapes and filled the atmosphere with poisonous gases and debris. Life on earth began choking to death. Some of the areas on the earth became full of geothermal springs and the air became thick with sulphurous fumes and carbon monoxide.
As a comet hit earth, a shower of molten rock began to fall. The comet struck the Gulf of Mexico with the force of 10 billion Hiroshima bombs. The catastrophic events that followed caused 65% of life on earth to die out. It took millions of years for the earth to recover, after such time, the dinosaurs were completely wiped out. Only one small group of dinosaurs did survive, the birds.
