Mass extinctions have a silver lining, providing opportunities for marginalized creatures to rise to power. While that notion seems obvious, it hadn't been demonstrated for the end-Permian extinctions, which occurred about 252 million years ago and wiped out about 90% of life on Earth. So, researchers took a detailed look at the numbers and distribution of land-dwelling species at five sites scattered across the southern part of Pangaea, the supercontinent that existed at the time of the die-offs. (Previous analyses had looked at only trends in marine species or for limited regions on land, the team notes.) Of the 62 species found at the sites about 5 million years before the die-offs, 21 (or about 34%) were found in two or more of the sites, suggesting a wide distribution of those creatures. But 10 million years after the end-Permian extinctions, only five species out of 68—none of which matched the 62 that lived before the die-offs—were found at more than one site. The analysis also reveals that after the mass extinctions, species typically had smaller, less-connected geographical ranges than did the species living before the die-offs, the researchers report online today in the Proceedings of the National Academy of Sciences. Altogether, the trends suggest that when widely prevalent creatures such as the pig-sized Dicynodon (left) were removed from the scene, species such as the 3-meter-long Asilisaurus (right)—a member of the archosaurs, which included dinosaurs and many groups alive today, such as crocodilians and birds—could diversify and thrive.
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*Correction, 9:25 a.m. on 30 April: This article has been updated to remove mammals from the list of living groups within archosaurs.