Mean atmospheric O2
Geologic Time Scale
Dilophosaurus amidst Williamsonia No. 2
A colorful adult male dinosaur theropod of the genus Dilophosaurus explores a hilltop populated by cycads of the species Williamsonia gigas, Sago Palms and ferns 180 million years ago in what is today North America.
Dilophosaurus is the first known predatory dinosaur. It grew up to 20 feet long, stood 8 feet tall, and weighed as much as a half ton. Dilophosaurus roamed the Earth 100 million years before its larger and more celebrated cousin Tyrannosaurus Rex roared onto the scene.
The tree-like Williamsonia gigas was a seed plant belonging to the order of Bennettitales and reigned for 130 million years before becoming extinct. Williamsonia gigas produced what appear to be large flowers, which were really a group of seeds surrounded by a crown of leaf-like structures known as bracteae. True flowers didn't begin to dominate the landscape until relatively recently--about 50 million years ago. The 0ther flora illustrated here live to this day, including evergreen coniferous trees of the genus Araucaria, ferns, and Sago Palms (which in reality are not palms but a type of gymnosperm).
Copyright © Walter B. Myers. All rights reserved.
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