Life › The age of dinosaurs › The Great Dying (end-Permian extinction)
Life recovers in the Triassic
c. 252–240 million years ago· Event· Animals
Strong evidenceGood evidence; dates or details still being refined.
The slow rebuilding of life after the Great Dying, through early Triassic heat and repeated setbacks.
See it on the Life map →What happened
The earliest Triassic was extremely hot, with tropical seas near 40°C in places and an equatorial belt where few fish or reptiles lived. Reefs were absent for millions of years, and a "coal gap" of about 10 million years shows that swamp forests had collapsed. Repeated carbon-cycle swings stalled recovery. By about 247–240 million years ago, new ecosystems had formed: modern-style corals and marine reptiles at sea, and archosaurs (crocodile and dinosaur ancestors) and mammal relatives on land.
Why it matters
It shows how long ecosystems take to rebuild after a crash, roughly 5–10 million years, and the new set of winners shaped the whole Mesozoic.
The evidence (fossils, genes, rocks)
Fossil sequences from South China, Svalbard, the western US and South Africa; oxygen isotopes in the teeth of conodonts (tiny eel-like animals) record temperature; carbon isotopes track the swings.
Still debated
Why recovery was so slow is debated: ongoing eruptions, heat, or slow rebuilding of food webs. Some groups, such as ammonoids, rebounded within a couple of million years.
Inside this (2)
Connections (4)
▸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.
▸Life recovers in the Triassic was dominated at first by LystrosaurusWell established
The connection
In the bleak earliest Triassic, Lystrosaurus became by far the commonest land vertebrate across southern Pangaea. With few competitors or predators, this burrowing plant-eater spread widely. Its dominance is a classic "disaster fauna": a few hardy generalists filling a landscape emptied by extinction.
When and how
Earliest Triassic, about 252–247 million years ago, in South Africa's Karoo Basin, India, China, Russia and Antarctica.
The evidence
Bed-by-bed fossil counts in the Karoo show Lystrosaurus vastly outnumbering other vertebrates just above the extinction boundary.
Debates and open questions
How long its dominance lasted, and how much the counts reflect true abundance rather than how fossils were collected, are discussed.
▸Life recovers in the Triassic saw the rise of Marine reptiles (ichthyosaurs, plesiosaurs, mosasaurs)Well established
The connection
As oceans refilled, reptiles found empty top-predator roles. Within about 4 million years of the extinction, ichthyosaurs and other marine reptiles appeared and diversified; by about 246 million years ago one ichthyosaur, Cymbospondylus youngorum, reached about 17 m. Their prey included fish and ammonoids, which also recovered quickly.
When and how
Early to Middle Triassic, about 248–240 million years ago; key finds come from Anhui and Guizhou in China, Nevada and Europe.
The evidence
Early ichthyosaurs and relatives occur in dated Early Triassic marine rocks, including Cartorhynchus from China, a small form that may have moved on land too.
Debates and open questions
Why so many reptile lines took to the sea so soon after the extinction, and which land reptiles were their ancestors, are debated.
▸Life recovers in the Triassic produced the first DinosaursWell established
The connection
Dinosaurs evolved from small archosaur relatives that diversified during the Triassic recovery. By about 233–230 million years ago, the first true dinosaurs appear in South America. Their early success was modest: they stayed secondary to other reptiles and mammal relatives for some 30 million years.
When and how
Late Triassic South America, in Argentina's Ischigualasto and southern Brazil's Santa Maria formations, about 233–230 million years ago.
The evidence
Fossils show dinosaur-like relatives such as silesaurids appearing first, followed by true dinosaurs, with radiometric dates bracketing both.
Debates and open questions
When dinosaurs first appeared, perhaps as early as 243 million years ago, and whether a wet climate spell, the Carnian Pluvial Episode, boosted them are debated.