Life › Seas, forests & the move to land
The Great Dying (end-Permian extinction)
252 million years ago· Extinction or crisis· Earth, climate & extinctions
Well establishedStrong fossil, genetic or geological evidence.
Earth's worst known mass extinction, which ended the Permian period about 252 million years ago.
See it on the Life map →What happened
Estimates vary, but roughly 80–90% of marine species and about 70% of land vertebrate species died out. The main pulse may have lasted only tens of thousands of years. Siberian eruptions released huge amounts of carbon, heating tropical seas toward 40°C, acidifying oceans and stripping them of oxygen. Trilobites vanished, reefs disappeared for millions of years, and insects suffered their only known mass extinction. Recovery took roughly 5–10 million years.
Why it matters
It reset life. Modern-style marine ecosystems, and the world of archosaurs and then dinosaurs, grew from the few survivors.
Think of it like
Like a crash that empties nine of ten storefronts on a street: the street fills again, but with different businesses.
The evidence (fossils, genes, rocks)
Bed-by-bed fossil counts from sections such as Meishan, China, the global reference site; precise uranium-lead dates from ash beds; carbon, oxygen and calcium isotopes recording heating and acidification.
Still debated
The exact kill sequence (heat, acid, low oxygen, toxic hydrogen sulfide, ozone loss) is debated, as is whether land and sea losses were exactly simultaneous.
Inside this (2)
Connections (10)
▸Sharks survived The Great Dying (end-Permian extinction)Well established
The connection
Sharks and their relatives lost many lineages in the Great Dying, but several groups, including the hybodonts and the ancestors of today's sharks and rays, made it through. In the emptied Triassic seas they diversified again, eventually producing the modern shark groups.
When and how
Oceans worldwide about 252 million years ago; shark teeth and fin spines appear in earliest Triassic marine rocks on several continents.
The evidence
Fossil teeth and spines below and above the boundary, plus family trees that trace living sharks back to Paleozoic ancestors.
Debates and open questions
How many shark lineages survived, and why, are uncertain. Cartilage skeletons rarely fossilize, so counts rely heavily on teeth.
▸Pangaea supercontinent set the stage for The Great Dying (end-Permian extinction)Debated
The connection
Pangaea's single landmass may have made life more fragile. Shallow coastal seas, home to much marine life, shrank as continents merged; the vast interior grew dry; and sluggish circulation in the one world ocean may have made it prone to losing oxygen. When the Siberian eruptions struck, these conditions may have magnified the damage.
When and how
Late Permian, about 260–252 million years ago, across the supercontinent and the surrounding Panthalassa ocean.
How sure are we?
The trigger is well supported (see the Siberian Traps). Pangaea's contributing role rests mainly on climate and ocean models, so it is debated.
Debates and open questions
Whether Pangaea weakened ecosystems beforehand or the eruptions alone were enough is unresolved; models disagree on how stagnant the ocean was.
▸Siberian Traps eruptions triggered The Great Dying (end-Permian extinction)Strong evidence
The connection
The eruptions released enormous amounts of carbon dioxide and methane, much of it by baking coal and limestone underground. Rapid warming, acidified oceans and seas losing oxygen followed, and halogen gases may have thinned the ozone layer. Together these stresses killed most species, perhaps within tens of thousands of years.
When and how
Siberia, about 252 million years ago. Precise dating by Seth Burgess, Samuel Bowring and colleagues (2014–2017) tied the deadliest eruption phase to the extinction.
How sure are we?
High-precision uranium-lead dates show eruptions began just before the extinction; carbon isotope swings and mercury spikes in boundary rocks worldwide record volcanic input.
Debates and open questions
Which gas killed most species, and why only some eruption phases were deadly, remain debated. Few scientists now doubt the link itself.
▸The Great Dying (end-Permian extinction) devastated Synapsids: the mammal lineStrong evidence
The connection
Before the extinction, therapsid synapsids ruled land, from tusked dicynodont plant-eaters to saber-toothed gorgonopsian predators. Most of their lineages died out. A few survivors, notably Lystrosaurus and small cynodonts on the line to mammals, carried synapsids into the Triassic, where archosaurs, the reptile line leading to dinosaurs, soon took the lead.
When and how
Land ecosystems across Pangaea about 252 million years ago, best recorded in South Africa's Karoo Basin and in Russia.
How sure are we?
Fossil counts from the Karoo and elsewhere show most synapsid species disappearing at or near the boundary.
Debates and open questions
Whether land losses were simultaneous with sea losses, and whether the Karoo shows one sharp pulse or a drawn-out decline, are debated.
▸Trilobites were wiped out by The Great Dying (end-Permian extinction)Well established
The connection
Trilobites had lived for nearly 270 million years but were already in long decline; by the late Permian only one order, the Proetida, remained. The Great Dying finished them off, ending a group that had been among the commonest animals of the Cambrian seas.
When and how
Late Permian seas; the last trilobites disappear at or just before the boundary about 252 million years ago.
The evidence
No trilobite fossil has ever been found in Triassic or younger rocks, despite more than two centuries of intensive collecting.
Debates and open questions
Whether the last trilobites died in the boundary crisis itself or slightly earlier is unclear, because late Permian trilobite fossils are rare.
▸The Great Dying (end-Permian extinction) was followed by Life recovers in the TriassicWell established
The connection
The extinction left a nearly empty world: few species, small body sizes, scarce reefs and forests. Recovery took roughly 5–10 million years, slowed by continuing heat and repeated carbon-cycle disruptions. Survivors and newcomers then built the ecosystems that set the pattern for the rest of the Mesozoic.
When and how
Earliest to Middle Triassic, about 252–240 million years ago, worldwide; well recorded in South China and South Africa's Karoo Basin.
The evidence
Fossil diversity counts climb through Triassic rock layers, and isotope records show the environmental swings that slowed the rebound.
Debates and open questions
Whether recovery was slow everywhere is debated; the Paris Biota of Idaho, described in 2017, shows a rich marine ecosystem only about 1.3 million years after the extinction.
▸The Great Dying (end-Permian extinction) opened the way for DinosaursStrong evidence
The connection
By wiping out most therapsids, which had ruled Permian land, the Great Dying left room for archosaurs, the reptiles that include the ancestors of dinosaurs, crocodiles and pterosaurs. Archosaurs diversified rapidly in the Triassic, and true dinosaurs appeared within about 20 million years of the extinction.
When and how
Pangaea, from about 252 million years ago; early archosaurs and dinosaur relatives are known from Russia, South Africa, Tanzania and Poland.
How sure are we?
Fossils show archosaurs radiating in the Early and Middle Triassic, and footprints from Poland suggest dinosaur cousins within a few million years of the extinction.
Debates and open questions
Whether archosaurs had a built-in advantage, such as upright posture or efficient breathing, or simply got lucky after the extinction is debated.
▸The Great Dying (end-Permian extinction) is one of the Big Five in Extinction & mass extinctionsWell established
The connection
The end-Permian extinction 252 million years ago is the largest in the record, killing roughly 80–90% of marine species. It anchors the very concept of mass extinction: an event so large that whole ways of life, such as trilobites and Paleozoic reefs, simply ended. Raup and Sepkoski ranked it first of the Big Five by size.
When and how
Defined at Meishan, China, the reference section for the Permian–Triassic boundary; quantified in 1982 by Raup and Sepkoski and in later fossil databases.
The evidence
Precise uranium-lead dates on volcanic ash at Meishan show the main die-off took perhaps 60,000 years or less; fossil counts across hundreds of sections confirm its scale.
Debates and open questions
Whether land and sea extinctions happened at the same moment, and which killer, heat, acid or oxygen loss, did most of the damage.
▸Lystrosaurus survived The Great Dying (end-Permian extinction)Well established
The connection
Lystrosaurus is one of very few dicynodont lineages known to cross the extinction boundary. Possible advantages include burrowing to escape heat, a beak and tusks for tough roots and stems, and breeding young. A 2016 study found that post-extinction individuals grew fast and reproduced early, as animals do in stressed populations.
When and how
Late Permian to earliest Triassic, about 252 million years ago, best documented in South Africa's Karoo Basin.
The evidence
Lystrosaurus fossils occur both below and above the boundary in the Karoo, and bone growth rings record how fast individuals grew.
Debates and open questions
Whether its survival came from its traits or from luck, and how many of its species crossed the boundary, are debated.
▸The Great Dying (end-Permian extinction) nearly wiped out AmmonitesWell established
The connection
Ammonites and their relatives, shelled cousins of squid and octopus, were common in Permian seas. The Great Dying cut them down to very few surviving lineages. Those survivors rebounded fast, diversifying again within a million or two years, and the group thrived until the asteroid impact 66 million years ago.
When and how
Seas worldwide about 252 million years ago; boundary sections in South China and Pakistan's Salt Range record the losses and the rebound.
The evidence
Fossil shells counted bed by bed show most groups disappearing at the boundary, followed by a burst of new Triassic forms.
Debates and open questions
How many lineages survived, perhaps only one or two, and why ammonoids recovered so much faster than most other groups are debated.