The Cretaceous Period

Benton, M.J. (2005). Vertebrate Palaeontology. Blackwell Publishing. Renne, P.R., et al. (2013). "Time Scales of Critical Events Around the Cretaceous-Paleogene Boundary." Science, 339(6120), 684-687.

Interesting facts: Flowering plants (angiosperms) first appeared during the Cretaceous Period and began to diversify. The period saw the evolution of the first birds, descendants of small theropod dinosaurs. The Atlantic Ocean began to open during this time as the continents drifted apart. While dinosaurs dominated the land, early mammals lived alongside them, often small and nocturnal to avoid predation. The Cretaceous seas were home to massive marine predators like Mosasaurus and Plesiosaurus. Ammonites, shelled marine creatures, thrived in the oceans but went extinct at the end of the period.

The Cretaceous-Paleogene Extinction Event occurred at the end of the Cretaceous Period. This catastrophic event, believed to have been caused by an asteroid impact, wiped out nearly 75% of Earth's species, including all non-avian dinosaurs. The impact caused a chain reaction of events, including massive wildfires, a global "nuclear winter" due to the debris blocking sunlight, and the collapse of ecosystems.Location of impact: The asteroid is thought to have hit the Yucatán Peninsula in present-day Mexico, creating the Chicxulub crater. Aftermath: The event paved the way for mammals to rise in dominance in the post-dinosaur world.

Climate: During the Cretaceous, the climate was generally warmer than today, with high levels of carbon dioxide and no polar ice caps. Sea levels were higher, and much of the planet was covered in shallow seas. Atmosphere: The atmosphere had a higher concentration of oxygen than today, which supported large and diverse life forms. Geography: The continents were starting to drift apart, breaking up the supercontinent Pangaea. This created a range of environments from coastal seas to expansive forests. Organisms: Dinosaurs dominated the land, with famous species such as Tyrannosaurus rex, Triceratops, and Velociraptor. In the seas, large marine reptiles like Mosasaurus ruled, while the skies were patrolled by giant pterosaurs.

The Cretaceous is a period within the Mesozoic Era, which is part of the Phanerozoic Eon.

The Cretaceous Period lasted from approximately 145 million years ago to 66 million years ago—a span of about 79 million years.

The Cretaceous Period