The Permian world- life on the supercontinent ⋆ TheScientificRevelation

Nǐ hǎo friends. Welcome to another post of the scientific revelation’s “History of the earth series”. In this post, we will discuss the Permian world and how life survived in the harsh conditions of the supercontinent. Although all the modern countries were united in the Permian period it wasn’t very picnic-like on Pangea. Let me explain what it was like to live on a vast joined land.

Firstly, Pangea was huge so the moisture from oceans couldn’t travel to the islands. In the simplest sense, the inside of continents was desert. A major chunk of Pangea, almost 60%, was practically inhabitable. The coastal boundaries of Pangea had the maximum excess moisture and monsoon rain consequently it was greener and lush. The coastal regions had rainforests and the most diversity in Pangea. Secondly, as clouds carried the leftover moisture to some distance it rained over grasslands. Grasslands-like places were transition zones between lush coastal rainforests and dry interiors. Now think about this scenario, habitable land is less with high competition. All animals can not squeeze in between 25–30% of land so some ventured towards hellish inland. These became the true rulers of the Permian and subsequent Mesozoic era- the age of reptiles.

disclaimer- The grass hasn’t originated yet so these grasslands were rather open places with some vegetation.

New World after the collapse of rainforests

Pangea started to assemble 335 million years ago but fully formed at the start of the Permian period approximately 299 million years ago. Do you people remember the end of the Carboniferous period? There were many interrelated reasons for the Carboniferous rainforest collapse. One of them was the spread of glaciers and how they lowered the sea level. These late carboniferous glaciers had survived in the Perian period and Gondwana had extensive glaciers in the early Permian period. moreover, in the early Permian despite a large supercontinent, some regions including the equator had damp conditions with rainforest. However, as the period preceded those rainforests shrunk and widespread deserts enveloped the major chunk of Pangea.

Read this post on the Permian period

The position of paleo continents

The main feature of the Permian period was Pangea, assembled at the boundary of the Permian and carboniferous period. There is one thing to keep in mind is that Pangea was not entirely intact in the early Permian. Continents move all the time due to plate tectonics. In the early Permian period continents were not entirely joined like a lock and key system instead they were in more of a loose fit. As the years passed on continents drifted more northwards, they came together. Consequently, when continental boundaries clashed with each other it had encouraged orogeny.

Orogeny is the process of mountain building. When continental plates crash into each other either one plate slides against the other or both plates rise upward. In any case mountain forms at the continental boundaries. If mountains have formed during the collision of oceanic and continental plates they are also accompanied by trench formation nearby in the oceanic plate.

Continental collision and mountain building

When Gondwana(from the south) collided with Laurasia or Euroamerican on the equator, Alleghenian orogeny happened. Mountains might have formed at the juncture point between North America and north-western Africa (Sahara region). At the end of the Early Permian period, the rest of the Pangaea had collided with Angara(part of Siberian craton) which gave rise to Uralian orogeny. Normally we consider the one continent-one ocean approach for Pangaea but in reality, the Pangaea had another smaller sea, Tethys ocean which became Atlantic in later years. The two oceans had extensive geologic features like trenches, volcanic islands, and oceanic plateaus scattered across. Permian had seen its fair share of seal level fluctuations.

At the start of the Permian period, sea levels were lower as we had mighty ice sheets down on the Gondwana. As the period proceeded and ice sheets melted sea levels had risen considerably. The global low stand and high stand had significantly affected animal diversification in the whole Pangea.

Paleoclimate and oceans

On Broadway, we can say the Permian period was dry and the reason behind it was the supercontinent Pangea. It is quite easy to understand that Pangea had different climatic conditions. Firstly, the inland was extremely dry as a desert. The clouds carried moisture from the ocean and shed it near continental boundaries. They didn’t have enough moisture to carry it inland because the landmass was simply too huge.

Secondly, the formations of mountains had acted as roadblocks and further stopped the clouds from moving. Wherever the continental plates had collided we saw orogeny. These high mountains had strongly affected the regional climate. For example, the mountain chain in east Africa had made Africa drier because they blocked the moisture from the ocean. At the start of Permian earth’s glaciers on Gondwana melted through the Permian period. The middle Permian was wet and warm and opposite to it late Permian was dry and hot.

In the northern part of Pangea two mountain chains formed. One had an east-west orientation and the other one had a north-south orientation. This had massively affected east-west atmospheric flow in the temperate region. Pangea had also influenced ocean circulation. As there was no space to flow warm equatorial currents traveled to the polar region which might have helped in glacier melting. Polar currents flew at the western boundary of Pangaea. In the later Permian desserts were common in tropical and subtropical areas taking the place of rainforests.

The continental collision had closed various shallow marine bodies that had persisted through the Ordovician period. These shallow marine ecosystems were a prime place for marine invertebrates that suffered immensely in the Permian period. Surviving species were confined to secluded water bodies. This had induced endemism because the separated water bodies had no contact with each other.

The end-Permian extinction

The great dying is the deadliest event for life on earth. It wiped out 95% of species on the ocean and 70 % of species on land. Only 10% of species all over the earth survived this catastrophe.

Permian had 3 epochs; early Permian, Middle Permian (Guadalupian), and late Permian (Lopingian). The great dying happened in the late Permian around 251 million years ago. Volcanism had heavily affected the late Permian. It was the strongest candidate for end Permian extinction (the great dying).

Volcanic eruptions and carbon envelope

Extensive Siberian volcanic eruptions (Siberian traps) and adjacent western china volcanoes erupted 250 million years ago. The eruptions were so iconic that within 600,000 years it had produced 2,000,000 to 3,000,000 cubic kilometers (480,000 to 720,000 cubic miles) of basalt. These volcanic eruptions had released extensive carbon dioxide and other harmful gases like sulfur compounds in the atmosphere.

These gases had put a deadly effect on life and the atmosphere. Firstly, gas clouds due to volcanic eruptions had enveloped the whole globe like a blanket. This cover had blocked the solar radiation from the sun for a long time. Consequently, photosynthesis dropped to a dangerous level. As plants were unable to photosynthesize they started dying. The fundamental level of the terrestrial ecosystem collapsed and it had brought devastation to animal life.

Gas clouds with high levels of sulfur compounds had also ruined the chemical compositions of the ocean and increased its acidity. Excessive gas became dissolved in water. In the ocean, super levels increased had oxygen levels dropped (hypoxia). Continuous acid rain had melted the rocks consequently increasing weathering. Weather material flew into the ocean making the tough life of marine animals tougher. These building chain reactions had brought the biggest catastrophe on earth, the end Permian extinction.

Life in the Permian period

Permian life is a good example of struggle, success, and stardom. Carboniferous was a wet and warm world that gradually transformed into a cold, seasonal world. With the onset of Permian, these cold and seasonal conditions persisted. They gradually turned into dry desert-like conditions as the period ended. It was an ever-changing environment and species had adapted according to the need of time. Ammonites had originated in the Carboniferous period and it is their time to shine. When Permian grew more dry and seasonal, amniotes basically reptiles radiated inland. They were able to tap the resources of inland because of their special characters. Some estimates suggested that oxygen levels were still higher at the start of the Permian period so perhaps large insects were living over Pangea.

Amniotes diversified into sauropsids and synapsids.

May the best animal live….

As speciation increased evolution had begun its magic and genetic diversity sored high. Higher genetic diversity means you could see niches were being occupied by specialized animals. Genetic diversity was highest in the Middle Permian (Guadalupian) epoch. However, in the late Permian, the true nature of dry Permian was showing up. The grouping of continents had taken a toll on the climate and it was becoming drier and drier. Many middle and early species weren’t able to cope up with these changes and they perished. Only a few hardy species had survived for the Lopingian epoch.

In the carboniferous lycopsids were dominant however in the Permian other plant species had taken up the stage. In the somewhat transition years of early Permian ferns dominated the earth but in the drier late Permian period seasonality had supported the rise of glossopteris. These were among the most successful plants of the Permian and subsequent Mesozoic era. Glossopteris’ fossils have been found on all the continents and it was one of the famous fossils for plate tectonic theory.

Early Permian had somewhat wet tropical conditions so ferns, seed ferns, and lycophytes dominated the forests. In middle to late Permian drier conditions had promoted glossopteris, coniferophytes (ginkgoes and cycads), proto-angiosperms( plant group predating true angiosperms). Insects migrated towards these new environments and diversified. These drier inland settings insects were preyed upon by ammonites instead of amphibians.

You may watch this video on the size comparison of the Permian period. It will get you an idea about what Permian animals were like.

Mammals and reptiles

Amniotes had raged high and strong in the Permian period. They diversified into two groups: sauropsids and synapsids. Sauropsids had given rise to reptiles and subsequently birds. Synapsids had given rise to mammals. To get things clearer sauropsids were reptile-like amphibians meaning they had reptile traits but still looked very much like amphibians. You can also call them stem reptiles. Synapsids, on the other hand, were stem mammals or mammals like reptiles. The Permian period

was the defining period for these groups. The funny thing is Mesozoic is called the age of reptiles but they were not dominant in the Permian period. In the Permian especially in the early epoch synapsids had diversified and modified enough traits to become a dominant species. Synapsids are called the world’s first terrestrial megafauna. Sauropsids took the center stage in the late Permian when conditions became adverse for synapsids. We are still why synapsids diversified better in early Permian.

Pelycosaurs- the early radiation of synapsids

By the end of the Permian period, the synapsids group had many adaptations that indicated the rise of mammals. Synapsids branched into two distinct groups. The reptile-looking synapsids are called pelycosaurs. They thrived in the early Permian taking over the wet environment. Pelycosaurs leaned more towards herbivory. Because of the plant diet, the belly or stomach portion of Pelycosaurs was the biggest part of its body. Due to its plant dependency Pelycosaurs had developed specialized teeth and jaws for crushing plant material.

By the end of the early Permian about 271 million years ago synapsids dominated the land because they were able to take advantage of the environmental conditions. just a reminder that early Permian still had rainforests and pretty wet conditions near equator regions that were transforming into deserts as the period passed. Dimetrodon was a Pelycosaurs that had a large sail-like structure. Many researchers think that sail was a Thermoregulating structure that helped in regulating the temperature. Many also believe that it was a defense mechanism that gave dimetrodon an imposing look to shoo away predators.

Therapsids and mammal link

By the middle Permian when the environment became more seasonal and dry a new kind of synapsids, therapsids grew to dominancy. therapsids were the dominant species in the middle Permian from 271 to 265 million years ago. Mammals have evolved from therapsids. These therapsids had developed particular teeth for different purposes like Anteosaurus had canine teeth for ripping flesh apart and chewing it.

sauropsids, on the other hand, jaws for Rip apart meet and swallow it whole. Reptiles and birds that have originated from sauropsids still do this today. Therapsids have developed more muscular jaws, active feet for running, and long necks which all mammals have inherited. Therapsids have basic thermoregulation akin to their active lifestyle. We have a high collection of fossils from Gondwana, which was the southern supercontinent.

Therapsids and gondwana

Gondwana’s glaciers had melted in later Permian due to the greenhouse effect but till the middle Permian ice sheet was still present in the Gondwana. It seems like therapsids had no problem in colds, which again explains that they were capable of thermoregulation. Therapsids were active predators and their body adaptations also support this theory. Because of their active lifestyle they might have been able to survive in cold conditions. For example, when we run fast cold doesn’t bother us much. This was the same case with therapsids. They survived well in the drier savannah-type conditions of the middle Permian period.

Some fossil evidence also suggests that few late Permian therapsids had hairs, prime character for thermoregulation. cynodonts were the last advancement in the therapsids group with all the traits described above. cynodonts survived the great dying and later gave rise to mammals in the Mesozoic era. After synapsids perished sauropsids basically reptiles had risen to the top in the middle Triassic period.

The famous Permian fossils include Pelycosaurs, aquatic reptilian ancestors to archosaurs. Archosaurs include dinosaurs, crocodiles, and birds. Stem reptiles mean reptiles like amphibians. It also includes eosuchians, early ancestors of snakes and lizards and anapsids, ancestors of turtles. Permian rocks have extensive fossils of sauropsids and synapsids. We can see a clear transformation if we compare the fossils of synapsids from Permian and true mammals from the Late Triassic. This fossil record of an 80 million year span tells us the brilliant evolutionary history of mammals.

Resources:

1. The most extensive post written on the Permian period by Bratannica.com.
2. Two good lectures on the Permian period by Thomas Evans and Historical Geology.
3. You may read this post on the Permian period- climate, animals, and plants by The Live science.

Permian was a turbulent time to be around like any other geologic period. Although, there is a catch when we talk about Permian. It indeed ended with the worst mass extinction but it gave mammals a great legacy. We are still unsure as to why Therapsidswent extinct (except one group) in great dying. Was it a pure chance or they were simply not adapted to live in post extinction world. We shall read more about Permian flora and fauna in upcoming posts. Until then stay tuned and Do Revelation.

Originally published at https://www.thescientificrevelation.com on August 3, 2021.