Cretaceous (145–66 Ma)

Origin of flowering plants

The Cretaceous Period is in the Mesozoic Era, occurring after the Jurassic Period, and before the Cenozoic Era. The Cretaceous Period is the last period in the Mesozoic Era.

What happened during this time?
  • Increased northern and southern regional differences in floras. 
    • First flowering plants appear on the landscape
    • Forests evolved to look similar to present day forests, with oaks, hickories, and magnolias becoming common in North America by the end of the Cretaceous.
  • New kinds of dinosaurs appear
    • First ceratopsian
    • First pachycepalosaurid dinosaurs 
  • First fossils of many insect groups
  • Modern mammal groups arise
  • Birds evolve from therapod lineage
  • Extinction of non-avian dinosaurs and ammonites
  • Pangaea rifting apart during Early Cretaceous; split in separate continents by the Late Cretaceous
    • Large-scale geographic isolation, causing a divergence in evolution of all land-based life for the two new land masses
    • Extensive new coastlines, and a corresponding increase in the available near-shore habitat. 
  • Seasons grow more pronounced as the global climate became cooler
  • At end of the Cretaceous Period, an asteroid hits Earth in the Yucatan Peninsula, Mexico, forming what is today called the Chicxulub impact crater
    • Chicxulub bolide was an asteroid 6 miles in diameter, collodes with Earth between 66.03 - 66.04 Ma (Renne et al. 2013)
    • It has been estimated that half of the world's species went extinct at about this time, but no accurate species count exists for all groups of organisms
    • Some have argued that many of the species to go extinct did so before the impact, perhaps because of environmental changes occurring at this time