Mesozoic Era (Age of the Dinosaurs) 225,000,000 years ago to 65,000,000 years ago Warm Climate Three Periods TriassicJurassicCretaceous

Mesozoic Era Triassic Period ( MYA) Pangaea (supercontinent) formed

Mesozoic Era Triassic Period ( MYA) First Dinosaurs (small in size) Pisanosaurus Length:3 feet Height:1 foot Weight:15 pounds Eoraptor: Length:3 feet Height: 1 foot Weight:20 pounds

Mesozoic Era Triassic Period ( MYA) Conifers and Cycad Forests Dominate (Gymnosperms)

Mesozoic Era Jurassic Period ( MYA) Pangaea starts to separate

Mesozoic Era Jurassic Period ( MYA) 1st mammals (small rodents).

Mesozoic Era Jurassic Period ( MYA) 1st birds (Archaeopteryx). Jaws and bone structure like dinosaurs Bones are hollow, like birds Had feathers

Mesozoic Era Jurassic Period ( MYA) Reptiles in the sea - Icthyosaurs – 8 m; Plesiosaurs – 15 m.

Mesozoic Era Jurassic Period ( MYA) Dinosaurs Dominate: Allosaurus, Diplodocus, Brachiosaurus, Stegasaurus.

Mesozoic Era Cretaceous Period ( MYA) Continents in modern positions

Mesozoic Era Cretaceous Period ( MYA) Flower plants (angiosperms) evolve & dominate

Mesozoic Era Cretaceous Period ( MYA) Dinosaurs still dominate: T. rex (carnivore); Triceratops (horned); Trachadon (duck- billed)

Mesozoic Era Cretaceous Period ( MYA) Mass Extinction: 50% of all plant and animal groups die out Alvarez’s Meteor Impact Theory- 10 km wide meteorite hits Earth

Mesozoic Era Cretaceous Period ( MYA)  Evidence of Impact: Iridium An element that is very rare in Earth rocks and very common in meteorites The layer of rocks above the last dinosaur bones contain ~ 160x normal levels of iridium Called the K/T Boundary

How could a meteorite impact cause a mass extinction?  The impact caused shock waves, tidal waves, and sent a tremendous amount of dust into the atmosphere  As the dust re-entered the Earth’s atmosphere, it would have instantly heated the atmosphere causing tremendous forest fires  Dust from impact blocked out the sun and caused major climate change and plants to die  Plants, animals, etc. went extinct due to the climate changes and competition between organisms

Cenozoic Era (Age of the Mammals) 65,000,000 years ago to Present Day Two Periods TertiaryQuaternary

Cenozoic Era Tertiary Period (65 MYA to 1.8 MYA)  Warm and humid climate  Mammals dominate: increasing in size  Earliest prehistoric humans (approx. 4 MYA).  Flowering plants (angiosperms) dominate  Grasses develop, grazing animals become even larger

Animals of the Tertiary Organisms that have been found in the La Brea tar pits of Los Angeles Megatherium, a giant ground sloth (20 ft long).

Animals of the Tertiary Indricotherium, measured up to 13 ft at the shoulder. Diatryma, a giant predatory bird.

The Great Ice Age

Cenozoic Era Quaternary Period (1.8 MYA to Present)  The “Great Ice Age”, ice sheets covered 30% of all land  Land & ice bridges connected many continents allowing animal migration  North American elephants (mastodons, mammoths), giant sloths & armadillos, and saber-toothed cats go extinct.  Modern humans evolve, maybe causing the above extinctions from over hunting.

A Sixth Mass Extinction? Are we the cause of a sixth mass extinction that is currently taking place? –Round Table Discussion