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Why did rugose and tabulate corals disappear at the end of the Permian?
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Permian extinction
The diversity of marine animal families since late Precambrian time. The data for the curve comprise only those families that are reliably preserved in the fossil record; the 1,900 value for living families also includes those families rarely preserved as fossils. The several pronounced dips in the curve correspond to major mass-extinction events. The most catastrophic extinction took place at the end of the Permian Period.
The disappearance of rugose and tabulate corals at the end of the Permian was part of the most extensive mass extinction in Earth's history, which eliminated 85 to 95 percent of all marine invertebrate species. While the exact combination of factors remains a subject of scientific study, several environmental crises are identified as primary drivers:12
- Temperature Extremes: Research suggests that ocean surface temperatures reached levels (potentially 30–32 °C or 86–90 °F) that were lethal for many marine invertebrates. One hypothesis posits that the photosynthetic symbionts living within the tissues of these corals could not survive the heat and abandoned their hosts, depriving the corals of a critical survival mechanism.3
- Oceanic Anoxia: Evidence from organic-rich, pyritic shales suggests that widespread oceanic anoxia—a lack of dissolved oxygen—devastated marine ecosystems, particularly affecting bottom-dwelling organisms like corals.1
- Ecological Stress: These corals were already struggling due to a series of extinction episodes that spanned approximately 15 million years, significantly reducing their diversity and resilience before the final terminal crisis.4
These cumulative environmental shifts ultimately rendered the environment unsustainable for these Paleozoic reef-builders.14