Mean atmospheric O2
Geologic Time Scale
Middle Jurassic ammonites
Mollusks of the subclass Ammonoidea in a Jurassic sea 170 million years
ago. The planispiral shells are about 30 inches in diameter,
making them among the larger known ammonites. Also in this image are ray-finned
fish of the infraclass Teleostei and jellyfish of the order Scyphozoa.
Copyright © Walter B. Myers. All rights reserved.
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