Mean atmospheric O2
Geologic Time Scale
A marine arthropod of the genus Pterygotus as it may have appeared 432 million years ago. The Pterygotus in this image is about five feet long. Other fauna in this image include trilobites of the genus Phacops and sessile polyps of the order Actiniaria.
Pterygotus is from the extinct order eurypterida (Sea Scorpion), and characterized by a pair of large compound eyes, as well as a pair of smaller eyes atop its head. It had 4 pairs of walking legs, a fifth pair modified into swimming paddles, and a pair of large pincers for grasping prey.
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