The Permian Period – The Great Mass Extinction

300 to 250 Million Years Ago

 

The geography of the Permian was spectacularly different from today. All the continents had joined together to form the great supercontinent of Pangea. With one ocean and one land mass, the climate of Earth began to warm and become more arid.

A significant factor in the Permian was the dramatic drop in oxygen levels. After reaching its high during the Carboniferous, oxygen began to disappear from both the atmosphere and the oceans, severely impacting all walks of life with one exception: plants, which thrive on carbon dioxide.

Paradoxically it was the rising carbon dioxide levels that most significantly affected the plants. As CO2 levels rose, plant life flourished for a while; but then the world became warmer and drier to the point that plants could no longer cope with the excessive heat and aridity.

It was also a time of many spectacular innovations. Diapsids, forerunners to the reptiles, began to gain in numbers and variety, eventually producing, by the end of the period, the Archosauromorphs, the ancestors of the dinosaurs. Alongside the diapsids, were early forms of Synapsids, the line that would spawn mammals at the end of the Triassic Period.

For the first time animals had four-chambered hearts, while other possessed endothermic capabilities that would allow them to regulate their own body heat. Both adaptations enabled the more efficient use of oxygen as oxygen levels continued their decline.

The Permian Period was an age of environmental extremes ending with the near-collapse of Life on Earth. During this great mass extinction approximately 90-95% of Life was annihilated, yet there is little certainty as to the cause of this horrific event.

Oxygen, Carbon Dioxide and the Atmosphere

• Oxygen levels were very high at the start of the period but dropped precipitously, impacting every form of life in dramatic ways.
  
• Animals produced varying forms of body plans that could more easily adapt to low oxygen levels. The stress of this environment encouraged a tremendous amount of experimentation and diversification.
  • One significant innovation was endothermy – the ability to regulate one’s own body temperature without depending on the exterior environment. This allowed the more efficient use of oxygen.
  • Another development that allowed animals to adapt to low oxygen levels was the four chambered heart. It also allowed the more efficient use of oxygen.
    
• Marine environments became toxic as oxygen levels fell. Many marine areas became uninhabitable.
  
• Low oxygen levels (about 15%) became so severe that the available oxygen at sea level would have been equivalent to our modern day altitude of 15,000 feet.
  
• Carbon Dioxide levels rose dramatically from their all-time lows.
• Methane levels increased and, along with higher carbon dioxide levels, led to significant global warming
  

Geography – Continents and Oceans

• For the first time since the early Cambrian, all the continents were once again joined together in a great supercontinent called Pangea that stretched from pole to pole.
• Covering most of the Earth’s surface is the Panthalassa Ocean which, along with the small Tethys Sea in eastern Pangea, comprised the two major bodies of water.
  

Climate

• Because the landmasses were joined together in one large body, the central areas of Pangea became dry with notable seasonal fluctuations. The trend toward aridity continued until deserts and sand dunes were common, replacing the humid swamps of the Carboniferous.
  

Plant Life

• Gymnosperms continued to diversify, producing many familiar modern forms such as the conifer, the ginkgo and the cycad.
  
• The seed ferns lost their long-held position as the dominant plant type.
• The increasing success of gymnosperms reflects the growing seasonality of the climate where the protection of offspring (encased in seeds) became essential as conditions became less stable and predictable.
  
• Plants also faced a growing threat from both insects and vertebrate herbivores.
  

Animal Life

• Many groups continued to diversify and experiment with different body plans, especially among the amphibians, diapsids (early reptiles) and the synapsids (early mammals). According to some scientists, it is believed that this considerable effort at diversification was a direct result of worsening levels of oxygen and carbon dioxide.
  
• Insects
  • The first insects undergoing metamorphic stages appeared: beginning life as an egg, progressing to a larva, then on to the pupa and adult stages. These stages enabled the insects to more easily cope with the unpredictable climate changes since each stage of life requires a different set of resources for survival.  Therefore if climatic and environmental conditions changed in any direction, the odds were good that at least one of the stages of the insect would be able to survive and sustain the species. 
  • Insects with foldable wings appear. This contrasts with the dragonfly which could not fold its wings and remained vulnerable to wing damage. Many of these new Permian insects were similar to cockroaches and proved very successful during this time.
  • The first herbivorous insects appeared.  Fossilized vegetation shows never-before-seen signs of insect damage.
  • The giant insects from the Carboniferous disappeared by the middle of the Permian with the decline of available oxygen.
    
• Reptiles and Mammal-Like Reptiles
  • The first vertebrate herbivores emerged (large slow-moving creatures, some weighing as much as 1300 pounds). This change to a vegetarian diet required adaptations: for example, grinding molars were required to chew the tough, fibrous plant matter, while large abdomens provided plenty of room for massive digestion systems able to process tough plant matter.
    
  • The Synapsid line (from the Carboniferous) branches off into the Therapsids early in the Permian. It is from these Therapsids that all modern mammals arise.
  • Towards the end of the Permian, the Archosaurs appeared. Surviving the Permian Extinction, this line would go on to dominate the Mesozoic Era, producing the dinosaurs in all their variety.
• Marine Life
  • Amphibians of all sizes and types are abundant during the Permian.
  • The great diversity of marine fauna from the Carboniferous continues to flourish in the Early Permian; as conditions worsen from the middle of the period on, small gradual extinctions occur until the final mass extinction at the end of the period.

  • As the continents coalesced into one large landmass, the amount of available shorelines and shallow waters decreased, thereby reducing the available habitat for marine flora and fauna that preferred sunlit shallow waters.

Mass Extinction

• The Permian Extinction was the greatest mass extinction of life on earth. As much as 95% of life was eliminated.
  • Marine life was heavily impacted eliminating most of the marine invertebrates. As much as 90% of the marine species were wiped out.
  • Trilobites, which had existed since the Cambrian in their myriad of fantastic forms, were unable to withstand the forces of this great extinction and we have to reluctantly bid them farewell from the fossil record. Bye, Bye, Trilobite.
    
  • Insects suffered their greatest extinction in Earth’s history.
    
  • The plants suffered a loss of about 60% of their genera. (As a means of comparison, a genus in animals would be the Canis (dog) and Equus (horses). Imagine the impact on the animal kingdom if 60% of these genera (plural of genus) were gone!)
    
• Possible Causes of the Extinction.
  
  • Eruption of the volcano complex known as the Siberian Traps. These eruptions lasted for about 1 million years.
    
  • A drop in the oxygen levels, both in the oceans and atmosphere.
    
  • Depletion of the ozone layer.
    
  • Eruption of the methane hydrates in the oceans.
    
• Even though the Permian Extinction was a close call for this planet, the dawn of the Mesozoic would mean the development of many significant and astounding types of life to fill the gaps left by this extermination.