Prehistoric Fish Extinction Paved the Way for Modern Vertebrates; Event of Unknown Origin Occurred as First Vertebrates Tested Land

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A mass extinction of fish 360 million years ago hit the reset button on Earth's life, setting the stage for modern vertebrate biodiversity, a new study reports.

The mass extinction scrambled the species pool near the time at which the first vertebrates crawled from water towards land, University of Chicago scientists report. Those few species that survived the bottleneck were the evolutionary starting point for all vertebrates -- including humans -- that exist today, according to a study published in the Proceedings of the National Academy of Sciences.

The Devonian Period, which spanned from 416 to 359 million years ago, is also known as the Age of Fishes for the broad array of species present in Earth's aquatic environments. Armored placoderms such as the gigantic Dunkleosteus and lobe-finned fishes -- similar to the modern lungfish -- dominated the waters, while ray-finned fishes, sharks, and tetrapods were in the minority.

But between the latest Devonian Period and the subsequent Carboniferous period, placoderms disappeared and ray-finned fishes rapidly replaced lobe-finned fishes as the dominant group, a demographic shift that persists to today.

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