Phanerozoic Eon: Mesozoic Era ➢ Permian extinction marks boundary between Paleozoic and Mesozoic eras ➢ The Age of Dinosaurs: Its rise and fall ➢ Consistently hot climate and dry terrestrial environments, little if any ice caps at poles
❖ Phanerozoic Eon: Mesozoic Era: Triassic Period ➢ 248-206 mya ➢ Reptiles plentiful: crocodiles and turtles ➢ First dinosaurs ➢ First true mammals ➢ Gymnosperms dominant land plant ➢ Volcanic eruptions led to global warming and mass extinctions near the end ❖ Phanerozoic Eon: Mesozoic Era: Jurassic Period ➢ 206-144 mya ➢ Gymnosperms continued to be dominant ➢ Dinosaurs dominant land animal ■ Some attained enormous size ➢ First known bird ➢ Mammals present but not prevalent ❖ Phanerozoic Eon: Mesozoic Era: Cretaceous Period ➢ 144-65 mya ➢ Dinosaurs still dominant on land ➢ Earliest flowering plants, angiosperms ➢ Another mass extinction at the end of the period ➢ Dinosaurs (except birds) and many other species died out ➢ Large meteorite/asteroid or volcanic eruptions blamed ❖ The Cretaceous Mass Extinction ➢ Likely meteorite impact at 65.5 mya, Mesozoic/Cenozoic boundary ➢ Organisms that went extinct include about half of all marine species and many terrestrial plants and animals, including most dinosaurs ➢ The presence of iridium in sedimentary rocks suggests a meteorite impact about 65 million years ago ➢ Dust clouds caused by the impact would have blocked sunlight and disturbed global climate ❖ Phanerozoic Eon: Cenozoic Era ➢ Spans most recent 65 million years
➢ Tropical conditions replaced by a colder, drier climate ➢ Sometimes called The Age of Mammals ➢ Amazing diversification of birds, fish, insects, and flowering plants ❖ Phanerozoic Eon: Mesozoic Era: Tertiary Period ➢ • 65-1.8 mya • Mammals that survived expanded rapidly • Birds and terrestrial insects diversified • Angiosperms become the dominant land plant • Fish diversified, sharks become abundant • Whales appeared • Hominids appeared about 7 mya ❖ Phanerozoic Eon: Mesozoic Era: Quaternary Period ➢ 1.8 mya to present ➢ Periodic ice ages cover much of Europe and North America ➢ Widespread extinction of many species ➢ Certain hominids become more human-like ➢ Homo sapiens appear 130,000 years ago ❖
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- Fall '09
- Extinction event, Cretaceous–Tertiary extinction event, Phanerozoic Eon