Mean atmospheric O2
Geologic Time Scale
Close-up of the face, eyes and antennae of a trilobite of the genus Phacops as it may have appeared 436 million years ago. The Phacops in this image is about six inches long.
A marine arthropod of the class Trilobita, Phacops is characterized by a rounded body with a globose head. Phacops, like most trilobites, had a pair of sophisticated compound eyes composed of hundreds of rigid, crystalline lenses.
Copyright © Walter B. Myers. All rights reserved.
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