Ecological Replacement: Jaws Did Not Dominate 420 Million years Ago

7/06/2011 07:59:00 PM ·

Over 420 million years ago, deep in the Silurian seas, some fish began developing a defined upper and lower jaw that allowed them to devour large and hard-shelled organisms.

The consensus seems to be that revolutionary mechanism did not set off a wild spree of evolutionary experimentation in design. Instead, after an initial bump of diversification—and a few exceptional mandibles in extinct placoderms and lungfishes—the major groups of jawed creatures whose descendents persist today, such as the ray-finned fishes and early tetrapods, seemed to stay relatively uniform.

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