Cretaceous

Definition

The Cretaceous is a geologic period that lasted from approximately 145 to 66 million years ago, marking the final era of the Mesozoic Era. It is notable for significant geological, climatic, and biological changes, including the diversification of dinosaurs, marine reptiles, and the appearance of early flowering plants, which collectively shaped Earth's ecosystems.

5 Must Know Facts For Your Next Test

1. The Cretaceous period is divided into two epochs: Early Cretaceous and Late Cretaceous, which saw varying climate conditions and biodiversity.
2. During this time, continents were shifting towards their current positions, creating diverse habitats for a variety of life forms.
3. Dinosaurs reached their peak diversity during the Late Cretaceous, with numerous species adapting to various ecological niches.
4. Marine reptiles like mosasaurs and plesiosaurs dominated the oceans during the Cretaceous, showcasing a rich marine ecosystem.
5. The end of the Cretaceous is marked by a mass extinction event likely caused by an asteroid impact, leading to significant changes in Earth's biodiversity.

Review Questions

• How did the environmental changes during the Cretaceous influence dinosaur diversity and evolution?
  • The environmental changes during the Cretaceous significantly impacted dinosaur diversity and evolution by providing varied habitats and resources. As continents shifted and climates changed, different ecological niches emerged, allowing dinosaurs to adapt and diversify. The Late Cretaceous in particular saw the rise of many new species as they exploited these environments, resulting in an extensive variety of forms ranging from small theropods to massive sauropods.
• Discuss the role of marine reptiles in Cretaceous ecosystems and their adaptations to marine life.
  • Marine reptiles played a crucial role in Cretaceous ecosystems as apex predators in oceans. Adaptations such as streamlined bodies, flippers for swimming, and specialized teeth for catching prey allowed them to thrive in various marine environments. Mosasaurs became dominant predators while plesiosaurs adapted to hunt differently, indicating a complex food web in the seas during this period. Their diversity reflects the rich and varied marine ecosystems that characterized the Cretaceous.
• Evaluate the causes and consequences of the mass extinction event at the end of the Cretaceous period.
  • The mass extinction event at the end of the Cretaceous period was likely caused by a combination of catastrophic events, including an asteroid impact and volcanic activity. This led to drastic climate changes and habitat loss that resulted in approximately 75% of species going extinct, including most dinosaurs. The consequences reshaped ecosystems globally, paving the way for mammals to rise in dominance during the subsequent Paleogene period and drastically altering evolutionary pathways on Earth.

Related terms

Mesozoic Era: The era that encompasses three geological periods: Triassic, Jurassic, and Cretaceous, known as the age of reptiles and characterized by the dominance of dinosaurs.

Paleogene: The geologic period that followed the Cretaceous, beginning approximately 66 million years ago, marked by the rise of mammals after the mass extinction event that ended the age of dinosaurs.

Mass Extinction: A significant and rapid decrease in biodiversity on Earth, particularly the mass extinction event at the end of the Cretaceous that wiped out nearly 75% of all species, including most dinosaurs.