Mean atmospheric O2
Geologic Time Scale
Ichthyostega and Rhacophyton
A three-foot-long Late Devonian tetrapod of the genus Ichthyostega emerges from waters of a floodplain 365 million years ago in what is today the Canadian Arctic. On the left is a four-foot-tall Rhacophyton ceratangium, a species of unclassified ancient shrub that is thought to be one of the earliest ferns. On the horizon are more Rhacophyton, along with towering tree-like plants with fern-like leaves of the genus Archaeopteris, and Lycopsids in various stages of growth.
Ichthyostega was one of the earliest tetrapods, a descendent of lobe-finned fishes and ancestor of amphibians. Ichthyostega had lungs and seven-toed limbs that allowed it to move about the shallow waters and shores of swamps and floodplains. It was among the first terrestrial vertebrates.
Copyright © Walter B. Myers. All rights reserved.
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