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New Study Revises Estimate Of The Greatest Mass Extinction
Metalegoceras, which is a cephalopod related to the living chambered nautilus. Credit: Falls of the Ohio State Park, Clarksville, Indiana (

Metalegoceras, which is a cephalopod related to the living chambered nautilus. Credit: Falls of the Ohio State Park, Clarksville, Indiana

A study published in the Proceedings of the National Academy of Sciences by Steven Stanley, paleontologist at University of Hawaiʻi at Mānoa, School of Ocean and Earth Science and Technology, revised estimates of the largest mass extinction to have taken place since animals appeared on Earth. It is undisputed that more than 250 million years ago, during the end-Permian “great dying” as it is commonly called, the number and diversity of marine species dropped catastrophically.

Stanley’s article introduces new methods for calculating the size of mass extinctions, that is, the percentage of species that died out during these crises. He devised a way to estimate the magnitude of background extinction—the extinction scattered throughout any mass extinction interval but having nothing to do with the mass extinction. Once Stanley had that number, he subtracted it out of the total to get a more accurate estimate of species loss.

“Most of these crises turn out to be less severe than previously believed, largely because people have calculated their magnitudes incorrectly by including background extinction,” said Stanley.

Cyclocrinites, a crinoid in the phylum Echinodermata suffered during the ‘great dying’ but survived and re-expanded. Credit: Fossils (Smithsonian Handbooks) by David Ward.

End-Permian crisis

There are several mass extinctions that stand out as having been extremely severe, and paleontologists have long recognized that the end-Permian crisis was the largest of all. A misleading scientific publication appeared in 1979 which mistakenly lumped together two mass extinctions and concluded that between 88% and 96% of marine species died out at the end of the Permian. This led to widespread claims that life nearly died out at the end of the Permian.

“Separating out the extinctions that actually occurred in the latest Permian, I have now estimated that the terminal Permian crisis eliminated only about 81% of marine species,” said Stanley. “About 90 orders and more than 220 families of marine persisted into the Mesozoic Era, the ‘Age of Dinosaurs,’ and they embodied an enormous amount of morphological, physiological and ecological diversity. Many of those species went on to diversify substantially. Life did not nearly disappear at the end of the Permian, as has often been claimed.”

This new study provides a more accurate picture of the history of life on Earth.

This Post Has 4 Comments
  1. I love your work, love that you study the timelines and are advanced enough to give scientific data background to what we now have in print from your work. The Ocean is our inner world here on earth and to know it will bring many rewards to humans. I look forward to hearing more.

  2. Thank you, Patricia. Actually, I have spent a great deal of time in, or partly in, the ocean. In order to interpret how extinct bivalve mollusks lived, for my dissertation, half a century ago (!), I studied the functional skeletal morphology of 95 marine bivalve species. I worked at the Woods Hole Oceanographic Institution, the University of Miami Marine Lab, and the University of Puerto Rico Marine Lab. I had only been to the ocean twice before in my life, and only once had I tasted its salty waters! — Steve Stanley

  3. 81% still seems very high. Is that the total amount of extinctions, or your recalculated amount w/o background extinctions? If the recalculated amount, then the total would be higher, yes? The total seems more relevant. So maybe still not too hyperbolic to say nearly all life extinguished. Even if it was only 81% total it would still make me very nervous:)

    1. Jonathon — The 81% is for the final event. The background extinction is not included because it occurred earlier.
      — SMS

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