Mean atmospheric O2
Geologic Time Scale
Allosaurus amidst Sequoias
A pair of dinosaur theropods of the genus Allosaurus search for dinner in the pre-twilight of a lush mountainside forest 150 million years ago in what is today North America. The orange "horns" on the foreground Allosaurus identifies this as an adult male, while his female companion behind attempts to make a meal of an unfortunate terrapin.
150 million years ago during the late Jurassic period, giant redwood coniferous trees of the genus Sequoia may have populated all of the northern continents. These evergreens grew as tall as 370 feet and some have trunk diameters exceeding 25 feet. The only living Sequoia today--and some are over 2,000 years old--occupy a narrow strip of land along the North American Pacific coast.
Some Allosaurus likely hunted in the shade of Sequoia. For 5 million years Allosaurus was the most common large carnivore in North America. Growing as long as 40 feet and weighing up to two tons, this fierce predator probably had few, if any rivals.
Copyright © Walter B. Myers. All rights reserved.
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