The Age of the “Great Extinction” 299 mya to 251 mya

1. THE HISTORY OF EARTHGeologic Time – Permian The Age of the “Great Extinction” 299 mya to 251 mya • Pangea supercontinent combines all major landmasses • Panthalassa combines all oceans except Tethys • Climate swings widely between hot and cold extremes • Huge deserts - Carboniferous swamp forests dry up • Egg-laying reptiles (Sauropsids) and mammal-like reptiles (Synapsids) proliferate wildly over the land. • Paleozoic Era ends with the Permian Mass Extinction –

2. THE HISTORY OF EARTHGeologic Time – Permian The Earth is coming out of the Carboniferous ice age so polar regions covered with deep layers of ice.  Tropics covered in swampy forests and the climate becomes warmer and milder as glaciers recede causing continental interior to became drier.  Eventually, much of the interior of Pangea is arid, with great seasonal fluctuations because of the lack of the moderating effect of nearby bodies of water.

3. THE HISTORY OF EARTHGeologic Time – Permian As the swamp land dried up many of the plants that needed the water died out. New plants developed that were adapted to the dryer conditions. They were called gymnosperms. These plants had seeds. Most of the trees living during the Permian period were conifers. Conifers are trees with seeds in cones.

4. THE HISTORY OF EARTHGeologic Time – Permian Conifers, ginkos and cycads, appear and thrive, spreading over dry Pangea. Ginkgois a genus of highly unusual non-flowering plant first appearing during the Permian. The rate of evolution within the genus has been slow, and almost all its species had become extinct by the end of the Pliocene; the exception is the sole living species, Ginkgo biloba, Cycadsare seed plants typically characterized by a stout and woody trunk with a crown of large, hard and stiff, evergreen leaves. They usually have pinnate leaves. They typically grow very slowly and live very long, with some specimens known to be as much as 1,000 years old. Although not common today, they surface during the Permian were were common during the Mesozoic.

5. THE HISTORY OF EARTHGeologic Time – Permian The changing climate affected how animals were evolving also. Amphibians dependent on swamps for a moist habitat began to die out as they found themselves out-competed by more adaptable reptiles. The reptiles could venture further onto dry land to lay their eggs. Two of the most notable amphibians of the early Permian were the 6-foot long Eryops Diplocaulus Diplocaulus had a stocky, salamander-like body, but was relatively large, reaching up to 1 metrein length. The early Permian Eryops was one of the largest amphibians in the history of life on earth So amphibians were replaced by the reptiles whose bodies could live in the very dry air and the wide changes in temperature.

6. THE HISTORY OF EARTHGeologic Time – Permian As the earth's climate became hotter and drier, these conditions favored small reptiles like Hylonomusand were detrimental to the amphibians who required water. Because reptiles were better at regulating their own body temperature, laid their eggs on land, and didn't need to stay close to bodies of water, the reptiles "radiated” occupying various ecological niches Orobatespabsti, Early Permian, Germany,

7. THE HISTORY OF EARTHGeologic Time – Permian One of the most important groups of "evolved" reptiles was the pelycosaurs which dominated the continent for about 40 million years. The most famous pelycosaur was Dimetrodon, a large reptile with a prominent sail on its back (the main function of which may have been to soak up sunlight and maintain its owner's internal temperature). The Dimetrodon could get as big as 11 feet long, weighing 500 pounds and ate meat.

8. THE HISTORY OF EARTHGeologic Time – Permian Two great branches of animal life appeared in the Permian. The Archosaursgrew into the crocodilians, dinosaurs and birds. The Therapsidsgrew into the Cynodonts, Mammals, and ultimately, humans. Chasmatosaurus was about 7 feet long and 100-200 pounds Moschopswas roughly 9feet with a short, thick and massive head.

9. THE HISTORY OF EARTHGeologic Time – Permian Archosaurs Archosaurs (Ruling Lizards) are Diapsids one of two classes of reptile, the other being Anapsids, meaning "without arches.” Archosaurs were the reptiles that led to the eventual rise of the dinosaurs from leaf-eating Stegosaurus, to the Brachiosaurus and the brutal Tyrannosaurus • Archosaurs are characterized by • Long, narrow snouts, and • teeth set in sockets (making them less likely to be torn loose during feeding)

10. THE HISTORY OF EARTHGeologic Time – Permian Dicynodon Therapsids • The Therapsids(mammal-like reptiles) were characterized by • powerful jaws bearing sharper (and better differentiated) teeth; and • upright stances (legs were situated vertically beneath their bodies, compared to the sprawling, lizard-like posture of earlier synapsids). The Therapsids were the most successful land animals of their day. The secret of their success was in their teeth, as therapsids evolved new and better methods of chewing plant and animal food. Therapsids take a beating in the mass extinction at the end of the Permian and are sidelined for millions of years as the dinosaurs diversified. The therapsids' ultimate successors - mammals - now rule the Earth courtesy of those efficient therapsid teeth and jaws.

11. THE HISTORY OF EARTHGeologic Time – Permian Cynodonts • Cynodonts are said to be the missing links between reptiles and mammals. It was during the evolution of the cynodonts that many things typical of mammals arose: • their jaw structure; • the hammer, anvil and stirrup bones of their inner ear; and • their efficient chewing teeth. • They may have been nocturnal, as the areas of the brain associated with smell and hearing - useful senses in the dark - were enlarged. Cynodonts("dog-toothed" reptiles) developed some distinctly mammalian characteristics. There's evidence that reptiles like Cynognathus and Thrinaxodon had fur, and they may also have had warm-blooded metabolisms and black, wet, dog-like noses. Cynognathus(Greek for "dog jaw") may even have given birth to live young, which by almost any measure would make it much closer to a mammal than to a reptile! Thrinaxodon

12. THE HISTORY OF EARTHGeologic Time – Permian Mass Extinction Theories Pangaea’s land mass stretching from pole to created extremely hot, dry conditions across most of the interior. By the Late Permian, global temperatures were the highest they’d ever been.  The severe conditions meant vast numbers of land and marine species were at risk. And then something happened that tipped them over the edge. Volcanic Activity
Huge volcanic eruptions in Siberia over 600,000 years may have sent huge volumes of viscous basalt lava poured out across Siberia, covering an area roughly 7 times the size of France.  Massive clouds of gases belched out. The sulphur dioxide caused acid rain and global cooling. But this was only short-term. The temperature increased as the eruptions injected carbon dioxide into the atmosphere and yet more escaped from coal deposits exposed in the surrounding area. 

13. THE HISTORY OF EARTHGeologic Time – Permian Mass Extinction Theories Comets and Meteors
Another theory is that a comet or meteor could have hit the planet, setting off a series of events that would have caused changes to temperature and sea levels, including the formation of glaciers.

14. THE HISTORY OF EARTHGeologic Time – Permian Mass Extinction Theories Methane Release As the oceans warmed, frozen methane located in marine sediments may have melted. If so, the release of this potent greenhouse gas could have turned the planet’s temperature up even more. As well as being devastating for marine and land plants and animals, Late Permian environmental changes created anoxic conditions in the sea. This lack of oxygen caused additional widespread extinctions because it destroyed food chains.