Triassic period

Definition

The Triassic period is the first period of the Mesozoic Era, occurring approximately 252 to 201 million years ago, following the mass extinction event at the end of the Permian. This era marks a time of significant geological and biological evolution, setting the stage for the dominance of dinosaurs and the rise of reptiles as key terrestrial vertebrates.

5 Must Know Facts For Your Next Test

1. The Triassic period began after the largest mass extinction in Earth's history, which wiped out about 90% of marine species and 70% of terrestrial species.
2. During the Triassic, Pangaea was intact, leading to dry climates and vast desert regions in many areas.
3. This period saw the emergence of the first true mammals and dinosaurs, setting a foundation for future evolutionary developments.
4. The Triassic was marked by the diversification of reptiles, including early archosaurs that eventually gave rise to dinosaurs.
5. The end of the Triassic period was marked by another mass extinction event that contributed to the dominance of dinosaurs in the Jurassic period.

Review Questions

• What were the major geological changes during the Triassic period, and how did these changes impact biodiversity?
  • During the Triassic period, Pangaea was still intact but began to fragment towards its end. This supercontinent influenced climate patterns, creating vast arid regions that affected where species could thrive. As environments changed, many organisms adapted or went extinct, leading to a shift in biodiversity. The combination of these geological changes and ecological pressures helped set the stage for new groups of animals to emerge, such as dinosaurs and early mammals.
• Discuss how reptile evolution during the Triassic laid the groundwork for the dominance of dinosaurs in subsequent periods.
  • The Triassic period was crucial for reptile evolution, as it saw the rise of archosaurs, a group that would eventually lead to dinosaurs. The adaptive radiation during this time allowed reptiles to explore various ecological niches. With favorable environmental conditions and available resources, reptiles diversified rapidly. This evolutionary groundwork not only led to numerous forms of reptiles but also paved the way for dinosaurs to become the dominant terrestrial vertebrates in the Jurassic period.
• Evaluate the significance of mass extinction events at both the beginning and end of the Triassic period on subsequent evolutionary trajectories.
  • Mass extinction events at both ends of the Triassic period were pivotal in shaping evolutionary trajectories. The Permian-Triassic extinction event cleared ecological space for new life forms to emerge, enabling reptiles and mammals to thrive in post-extinction environments. Conversely, the Triassic-Jurassic extinction event eliminated many species but particularly opened up opportunities for dinosaurs to become dominant. Each extinction reshaped ecosystems and influenced which species survived and evolved into new forms, thereby driving significant evolutionary change.

Related terms

Pangaea: A supercontinent that existed during the late Paleozoic and early Mesozoic eras, which began to break apart during the Triassic period, influencing global climate and sea levels.

Archosauria: A clade that includes dinosaurs, pterosaurs, and modern birds and crocodilians, which began to diversify during the Triassic period.

Mass extinction: A significant and rapid decline in biodiversity on Earth, such as the Permian-Triassic extinction event, which shaped the evolutionary pathways of life in the Triassic.