Mesozoic Era

An era of cone-bearing seed plants

The Mesozoic Era (252-66 Ma) is in the Phanerozoic Eon, occurring after the Paleozoic Era, and before the Cenozoic Era.

Geologic Age

  • 251.90266.0 million years ago

  • Almost 190 million years long; 4% of geologic history



What happened during this time?


  • Coralline red algae appear

  • Most pteridophytic plants decrease in prominence across the landscape (e.g. arborescent clubmosses and horsetails)

  • Pleuromeiales survive during the Triassic and modern lycophytes, Lycopodiales, Selaginellales, and Isoetales survive throughout the Mesozoic

  • Modern ferns diversify during Mesozoic: Cyatheaceae tree ferns, Osmundaceous, Matoniaceous, and Dipteridaceous ferns

  • The ancestral zygopterid ferns survive into the Early Cretaceous

  • Modern horsetails, such as Equisetum, appear in the Triassic

Seed plant diversification


  • Archosaurs dominate during Early Triassic

    • Pterosaurs appear, the first flying vertebrates on Earth

    • Appearance of dinosaurs (archosaurs) around 243 Ma (Nesbitt et al. 2013)

  • Therapsids also dominate during Triassic

    • Cynodonts, dicynodonts, and gorgonopsids are present

    • First true mammals (therapsids) evolve from cynodonts appearing during the Late Triassic

  • Domination of dinosaurs (saurischian)

  • First squids and birds

  • First frogs and salamanders

  • 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