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Did the Permian extinction happen suddenly or over millions of years?

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Line graph showing the number of marine animal families from the Precambrian era to the present, with illustrations of key groups such as trilobites, ammonoids, marine reptiles, and diatoms. The graph highlights major extinction events and a rise to 1,900 living families today. — 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 duration of the Permian extinction is a subject of ongoing scientific debate, with evidence supporting both gradual and rapid interpretations.

Some geologists and paleontologists argue that the extinction occurred over a span of 15 million years during the latter part of the Permian Period. This perspective is supported by observations that many groups of organisms showed evidence of a gradual decline long before the end of the Paleozoic Era.12

Conversely, other researchers contend that the extinction interval was significantly more rapid, lasting approximately 200,000 years. Within this shorter timeframe, the majority of species loss is estimated to have occurred over a 20,000-year span near the end of the period.1

These varying timelines are often discussed alongside potential causes, such as the prolonged eruption of the Siberian flood basalts, which may have triggered oceanic anoxia and significant shifts in the carbon cycle over hundreds of thousands of years.32