How Does Life Recover After the Worst Extinction in History?

This is the Triassic, which began about 252 million years ago. The extinction that closed the Permian had taken around four in five species in the sea. The episode runs from the empty world to the great rain, about 232 million years ago. The cool south (South Africa, Antarctica). Lystrosaurus, about 3 ft (1 m) long, two tusks behind a horny beak, is nearly three in four backboned fossils in the Karoo's lowest Triassic rocks. Its Antarctic tusks carry tightly packed growth rings that suggest it may have spent the polar winter in something like hibernation; by its discoverers' account, the oldest known sign of it in a backboned animal. Thrinaxodon, about the size of a house cat, had nippers, a canine and cheek teeth, and probably slept out the dry season curled in its burrow. Its burrow-mate was the amphibian Broomistega. The sea (South China, Nevada, Monte San Giorgio). Parts of the sea recovered surprisingly early: a fossil bed about a million years after the extinction already holds a complex food web. Then tropical heat held life back again, with the sea near the equator probably at 100 °F (38 °C) or more. Chaohusaurus, an early ichthyosaur about 3 ft (1 m) long, is preserved giving birth. Cymbospondylus may have been over 55 ft (17 m) long; that length is an estimate, its 6½ ft (2 m) skull is not. Tanystropheus reached 17 to 20 ft (5 to 6 m), about half of it a stiff neck of only 13 bones, and two fossils have necks bitten clean through. The land rebuilt (the south, then southern Germany). Woods of Dicroidium, a seed fern, returned six to eight million years after the extinction. Cynognathus, an estimated 6½ ft (2 m) long, had stabbing canines and slicing cheek teeth. In the swamps, Mastodonsaurus, one of the largest amphibians ever, had a flat head up to 5 ft (1.5 m) long, and its lower fangs passed through holes in the roof of its mouth. The rain. About 234 million years ago, huge eruptions in Wrangellia, now part of western Canada and Alaska, probably set off a series of wetter phases over more than a million years. From around that time come some of the oldest well-dated dinosaur skeletons, in southern Brazil. In the Dolomites, dinosaur tracks are missing before the wet interval and are more than nine in ten of the tracks a few million years later. The timing suggests a connection, though it doesn't prove the cause. Next on this channel: when crocodiles lived in the Arctic. ━━━━━━━━━━━━━━━━━━━━ CHAPTERS 0:00 Two skeletons in one burrow 0:50 After the extinction 1:17 The cool south, and the animals that dug 4:14 The sea comes back early, then stalls 5:26 The land rebuilt 6:07 Hunters in the sea 7:39 The swamp 8:17 The rain, and the newcomers 9:36 How life came back ━━━━━━━━━━━━━━━━━━━━ Every episode:    • When Earth Was Alien — Every Episode   Four billion years of alien worlds. All of them were here. ━━━━━━━━━━━━━━━━━━━━ Reference images used in the making of this episode's artwork (all via Wikimedia Commons unless noted): Burrow with Thrinaxodon and Broomistega — V. Fernandez et al., PLOS ONE, CC BY 2.5 Thrinaxodon — Nobu Tamura, CC BY 2.5 Thrinaxodon skull — Smokeybjb, CC BY-SA 3.0 Quillwort — W. Carl Taylor, USDA NRCS, public domain Lystrosaurus — Nobu Tamura, CC BY 3.0 Lystrosaurus tusk section — Megan R. Whitney, Christian A. Sidor, Communications Biology, CC BY 4.0 Lystrosaurus bone sections — Jennifer Botha, PeerJ, CC BY 4.0 Broomistega — Smokeybjb, CC BY-SA 3.0 Chaohusaurus — Nobu Tamura, CC BY 2.5 Chaohusaurus mother with young — R. Motani et al., PLOS ONE, CC BY 2.5 Dicroidium frond — Gregory Retallack, CC BY-SA 4.0 Cynognathus — Nobu Tamura, CC BY 2.5 Cynognathus skull — Ghedoghedo, CC BY-SA 4.0 Cymbospondylus — Mariolanzas, CC BY-SA 4.0 Cymbospondylus skull — Mx. Granger, CC0 Tanystropheus skeletal — Fishboy86164577, CC BY 4.0 Tanystropheus torso and neck fossils — Neil Pezzoni, CC BY 4.0 Mastodonsaurus — Dmitry Bogdanov, public domain Mastodonsaurus skull — Ghedoghedo, CC BY-SA 3.0 Saturnalia — CaetaMS, CC BY-SA 4.0 One shot, the giraffe, is stock footage: Afzaal0001 via Pixabay, Pixabay Content License. Handle spelled in letters, not numerals: @fourbillionsummers Business inquiries: fourbillionsummers@outlook.com #Triassic #DeepTime #EarthHistory #Paleontology #MassExtinction