Large hippo-like mammal forerunner ("Placerias") that lived, and died off, during the Triassic. (National Park Service Image)
Who was boss before the dinosaurs?
September 22, 2015
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The Jurassic witnessed a world populated by dinosaurs. While giant plant-eaters munched their way through ferns and conifer forests, large carnivores chased them down for lunch.
At the height of the Age of Dinosaurs, they were found on every continent. They flourished in the warm environments of the time.
But, dinosaurs were not always so prominent. Fossil evidence shows that they arose about 230 million years ago during the Triassic period, but remained scarce as other reptiles took center stage. Many mammal forerunners, such as the large plant-eater Placerias, prospered. Huge crocodile-like animals like Smilosuchus were the top predators of the Triassic.
Paleontologists who study the fossil record have discovered that something big happened 200 million years ago that radically changed life on land and in the sea, paving the way for dinosaur diversification and prominence.
What happened was so momentous that it caused more than half of all life on Earth to go extinct. The large crocodile-like reptiles that had dominated the landscape were eradicated, as were many of the mammal forerunners.
Find out more about the events that opened the door for the Age of Dinosaurs. Join us on Thursday, October 8, 2015, for a "Smithsonian Science How" live webcast on How Fossils Explain the Rise of Dinosaurs, airing at 11 a.m. and 2 p.m. EDT on the Q?rius website. Paleontologist Dr. Hans Sues from the National Museum of Natural History will appear live to discuss and answer questions. Get teaching resources to support your webcast experience.
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CRITICAL THINKING QUESTION
To study dinosaurs, why do scientists rely on fossils instead of photographs?
Write your answers in the comments section below