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The first animal fossils were puzzling cushion or quill-shaped creatures. But after 541 MYA, at the beginning of the Paleozoic Era, the ocean floor began churning with an amazing variety of animals.

Earth Timeline Key

 

Scientist have closely studied rock layers and have divided the history of life into three major Eras.

The Paleozoic (“Old life”) holds the early story of life’s development and the first land animals.  The Mesozoic (“Middle Life”) records the age of dinosaurs. The Cenozoic Era (“Recent Life”) includes the age of mammals up to the present day.  

These eras were separated by massive events called “extinctions” in which much of Earth’s life was destroyed.  In fact, we now recognize 5 major extinction events in the last half-billion years in which some catastrophe forever changed our world.

 The great Permian Extinction almost extinguished all life on our planet. Our last extinction was the huge K-Pg meteor impact that wiped out the dinosaurs just 65 million years ago.

Fossil Time Line
 

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