THE MESOZOIC ERA "THE AGE OF REPTILES" Ages of the Mesozoic Era

The Mesozoic Era was the time from 248 million to 65 million years ago. During the Mesozoic, the Earth was very different than it is now. The climate was warmer, the seasons were very mild, the sea level was higher, and there was no polar ice. Even the shape of the continents on Earth was different; the continents were jammed together at the beginning of the Mesozoic Era, forming the supercontinent of Pangaea, but would start breaking apart toward the middle of the Mesozoic Era.

Toward the beginning of the Mesozoic Era there was a depleted ecosystem world-wide. Many of the old life forms had just gone extinct in the Permian Extinction, the world's largest mass extinction. This depleted state was followed by an explosion of new life forms, which included the dinosaurs and mammals, and later in the Mesozoic, the birds and flowering plants.

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The dinosaurs and the mammals appeared during the Triassic period, roughly 225 million years ago. The dinosaurs went extinct 65 million years ago.

The Mesozoic Era lasted about 180 million years, and is divided into three periods, the Triassic, the Jurassic, and the Cretaceous. Each of these periods is divided into many epochs and ages. Mesozoic means "Middle Animal" and is sometimes called the age of reptiles. The term Mesozoic was coined John Phillips in 1840.

The world's life forms were very different during the Mesozoic than either before or after. During the Mesozoic, dinosaurs dominated the Earth. After the Mesozoic, the Cenozoic or the "Age of Mammals" began. Forty percent of the known dinosaurs date from the last 15 million years of the Cretaceous period.

1. The earliest period of the Mesozoic Era was the Triassic period (248 - 208 million years ago), in which the first small dinosaurs and mammals developed. The Triassic began after a major extinction had wiped out most of the life forms on Earth. The end of the Triassic was also marked by a worldwide extinction, although minor in comparison.
2. The second period was the Jurassic period (208-146 million years ago), in which the dinosaurs began to flourish. Giant sauropods appeared along with many other dinosaurs. The first primitive birds and flowering plants (angiosperms) appeared.
3. The third Mesozoic period was the Cretaceous period (146-65 million years ago), which saw the height of the dinosaurs and the development of flowering plants. It ended with another extinction and the demise of the dinosaurs and many other prehistoric animals.

The Age of Reptiles	The Mesozoic Era 248 - 65 million years ago
	Triassic Period 248 - 208 million years ago	Jurassic Period 208-146 million years ago	Cretaceous Period 146-65 million years ago
Continental Drift	One supercontinent, Pangaea.	In mid-Jurassic, Pangaea began to break apart, into Laurasia and Gondwana.	Continental drift continued at a fast pace, with accompanying volcanic activity. The continents almost had their modern-day look.
Climate	Hot and dry, with strong seasonality.	Hot and dry, with strong seasonality at first, changing to warm and moist with no polar ice and vast flooded areas.	Temperatures were warm, seasonality was low, and global sea levels were high (no polar ice!) at the beginning of the Cretaceous. Later, sea levels dropped, seasonality increased, and there were greater extremes in temperature between the poles and the equator.
Plants and Animals	Small, fast dinosaurs appeared for the first time. The first tiny nocturnal mammals developed. Ichthyosaurs (marine reptiles) swam in the seas. Ferns , Glossopteris, cycads , horsetails, and early gymnosperms (conifers) abounded during the mesozoic.	More dinosaurs, including gigantic ones, roamed the earth, and pterosaurs flew. Archaeopteryx, the first primitive dinosaur-like bird developed.	Dinosaurs flourish. Flowering plants (angiosperms) spread, displacing conifers and others. The oldest-known ants, snakes, and butterflies arose towards the end of the Mesozoic Era. A major extinction occurred at the end of the Mesozoic, 65 million years ago.

PLATE TECTONICS
In 1912, the German geologist and meteorologist Alfred Wegener first proposed the theory of continental drift, which states that parts of the Earth's crust slowly drift atop a liquid core.

Wegener hypothesized that there was an original, gigantic supercontinent 200 million years ago, which he named Pangaea, meaning "All-earth".

Pangaea started to break up into 2 smaller supercontinents, called Laurasia and Gondwanaland, during the Jurassic period. By the end of the Cretaceous period, the continents were separating into land masses that look like our modern-day continents.

The fossil record supports and gives credence to the theories of continental drift and plate tectonics.

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