Mesozoic EraMesozoic Era(Age of the Dinosaurs)(Age of the Dinosaurs)

225,000,000 years ago225,000,000 years ago toto 65,000,000 years ago65,000,000 years ago

Warm ClimateWarm Climate

Three PeriodsThree Periods

TriassicTriassic

JurassicJurassic

CretaceousCretaceous

Triassic Period (225-180 MYA)

Pangaea (supercontinent) formed

Triassic Period (225-180 MYA)

First Dinosaurs (small in size)

Triassic Period (225-180 MYA)

Conifers and Cycad Forests Dominate (Gymnosperms)

Jurassic Period (180-135 MYA)

Pangaea starts to separate

Jurassic Period (180-135 MYA)

Dinosaurs Dominate: Allosaurus, Diplodocus, Brachiosaurus, Stegasaurus.

Jurassic Period (180-135 MYA)

Reptiles in the sea - Icthyosaurs – 8 m; Plesiosaurs – 15 m.

Jurassic Period (180-135 MYA)

1st mammals (small rodents).

Jurassic Period (180-135 MYA)

1st birds (Archaeopteryx).

Cretaceous Period (135-65 MYA)

Continents in modern positions

Cretaceous Period (135-65 MYA)

Dinosaurs still dominate: T. rex (carnivore); Triceratops (horned); Trachadon (duck-billed)

Cretaceous Period (135-65 MYA)

Angiosperms (flowering plants with fruit) evolve & dominate

Cretaceous Period (135-65 MYA)

Mass Extinction: 50% of all plant and animal groups die

Alvarez’s Meteor Impact Theory- iridium layer (common in meteors), dust blocked out the sun.

Cenozoic EraCenozoic Era(Age of the Mammals)(Age of the Mammals)

65,000,000 years ag65,000,000 years ago to to Present Dayo Present Day

Two PeriodsTwo Periods

TertiaryTertiary

QuaternaryQuaternary

Tertiary Period (65 MYA to 1.8 MYA) Warm and humid climate

Mammals dominate: increasing in size

Angiosperms (flowering plants) dominate

Grasses develop, grazing animals become even larger

Earliest prehistoric humans (approximately 3.5 MYA).

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

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 hunting.

A Sixth Mass Extinction?

• Are we the cause of a sixth mass extinction that is currently taking place?

– Round Table Discussion