Mesozoic Era: Age of Reptiles Chapter 13, Section 3

Mesozoic History The Mesozoic era spanned about 183 million years, and it is divided into three periods: the Triassic, Jurassic, and Cretaceous The Mesozoic era began with much of the world’s land above sea level (very few marine fossils are found in North America from the Triassic Period) In the Cretaceous, shallow seas invaded much of western North America creating great swamps (leaving large coal deposits) A major event of the Mesozoic era was the breakup of Pangaea This process lasted for 200 million years, forming the Atlantic Ocean It also caused the North American plate to override the Pacific plate, causing massive deformation, forming the Sierra Nevada and Rocky Mountains

The Breakup of Pangaea

Concept Check Explain how the Atlantic Ocean was formed. A rift developed during the breakup of a Pangaea that widened and eventually became the Atlantic Ocean.

Mesozoic Life When the Mesozoic began, its life forms were the survivors of the great Paleozoic extinction Gymnosperm – seed-bearing plant that bears its seeds on the surface of cones Unlike the first plants to invade land, gymnosperms were not restricted to living near the water’s edge, and they could take advantage of nutrients and space available in drier areas The gymnosperms quickly became the dominant plants of the Mesozoic Gymnosperm trees included the cycads, the conifers, and the ginkgoes Among the animals, reptiles readily adapted to the drier Mesozoic environment, being the first true land animals

Gymnosperms

Reptiles Dominate With the perfection of the shelled egg, reptiles quickly became the dominant land animals They continued this dominance for 160 million years Dinosaur – land-dwelling reptile of the Mesozoic era The reptiles made an amazing adaptation, one previously made by insects, they began to fly (the pterosaurs) Another group of reptiles led to the more successful flyers—the birds Some reptiles also returned to the sea, but retained their reptile teeth and breathed with their lungs At the end of the Mesozoic, many reptile groups became extinct Only a few types of reptiles survived to recent times (the turtles, snakes, crocodiles, and lizards) Most scientists believe that the extinction of the large reptiles was caused by a large meteorite that collided with Earth

Reptile Evolution

Pteranodon—The Flying Reptile

Concept Check How did reptiles become the dominant land animals? The development of shelled eggs allowed dinosaurs and other reptiles to dominate the land.

Assignment Read Chapter 13, Section 3 (pg. 377-381) Do Section 13.3 Assessment #1-5 (pg. 381) Print Out “Investigation 13 – Determining Geologic Ages"