Following the Carboniferous period, on the border with the Mesozoic era, the earth went through the Permian period. It happened between 299 and 251 million years BC It was the closing of the Paleozoic era.
Main events of the Permian period
There was an extinction event at the end of the Permian period, one of the largest ever recorded, it harmed the species existing until now. It affected a large number of organisms, especially those in marine environments. This is what happened with the vast majority of invertebrates.
Some groups survived but did not regain the ecological dominance they enjoyed in the past. This cleared the way for other groups to dominate marine life.
On land, diapsids and synapsids became extinct, paving the way for the dominance of other creatures.. Thus the terrain would be heading towards the Age of the Dinosaurs.
On the other hand, fern-like plants became gymnosperms. That is, in vegetables that reproduced through seeds. Modern conifers first appeared in the Permian fossil record. It was a time of great changes that would shape life on Earth.
© Max Bellomio
– Creative Commons
The territory
Global geography in the Permian was made up of massive areas of land and water. In its beginnings, the movement of the plates of the Earth’s crust had brought together much of the Earth in its entirety. It merged into the super-continent of Pangea.
This extended from the north pole to the south pole and most of the rest of the surface was covered by the Panthalassic Ocean. There was only one smaller sea west of Pangea which was known as Tethis.
Permian period stratigraphy
Until the late 1990s there was little consensus about the strata that constitute the Permian period. This is because the upper strata at locations from this period tend to be deficient in fossils. It has been difficult to carry out the correlation using the most appropriate indices.
An attempt was made to achieve a correlation using native fossils only from the regions where they were found. But the earliest work on the matter was based only on assumptions that have changed as the years have passed.
Current stratigraphy divides the Permian into three series or epochs, which are the following:
Cisuralian: from 299 to 270.6 million years BC Guadalupian: from 270 to 260 million years BC Lopingienese: from 260 to 252 million years BC
Permian shales, sandstones, siltstones, limestones, sands, marls, and dolomites were deposited as a result of sea level fluctuations. They are cycles of observable variations in rock layers. Relatively few sites lend themselves to direct radioactive dating, so the age of intervening strata is often estimated.
Some of the fossils that have been used include brachiopods, ammonoids, fusilinids, conodonts, and other marine invertebrates. Some genera date to such a specific time period that strata are named after them and allow stratigraphic identification through the presence or absence of specific fossils.
© Bramfab
– Creative Commons
Life in the Permian period
During this period the marine fauna specialized with the diversification of ammoids, brachiopods and bryozoans. Insects, amphibians and therapsids flourished, which were the precursors of mammals.
animal life
Reptiles thrived in water and on land. At this time there was a major transition in vegetation that resulted in the dramatic loss of coal swamps and amphibian habitats.
New types of insects such as beetles developed larval reproduction and adults used different ecological resources that affected the insect-plant and insect-predator relationship. In this way they achieved their greatest diversity of forms at all times.
Most of the major groups of terrestrial vertebrates occurred in the Permian. A wide variety of amphibians lived on land and in fresh water. Such is the case of Eryops a giant carnivore, and one of the large herbivores.
The main groups of amniotes, the synapsids, which were mammal-like reptiles, and the diapsids, which were pure reptiles, achieved great diversification. This included the first large vertebrate herbivores.
On the other hand, the carnivorous reptiles radiated towards many other forms of life. The adaptation to herbivory was the most important and complex that was achieved at that time. This is because the plant material requires special mechanical adaptations and specialized symbiotic relationships with fermentative bacteria.
plant life
Conifers and other xeric seed plants that had better adapted to the changing climatic conditions and xeric environments of the Permian also appeared and spread.
Competition in dry climate belts led to greater diversity and variability of seed plants. The continued evolution of arthropod herbivores and the first appearance of vertebrate herbivores encouraged plant evolution in new directions.
Since this is a transitional period, it saw the continuation of the Carboniferous biomes, with regions of polar tundra and warm, humid tropical swamp forests. However, the climatic trend during the Permian meant the death of the mighty swamp forests.
Water-loving plants such as lycopoid and sphenopidos, They were considerably reduced in size, turning them into mere shrubs. Ancient tropical carboniferous swamps with giant lycopods, calamites and cordaitals declined and disappeared as the climate became drier and colder. They only survived in China and in the high latitudes of Pangea. Plant life consisted mainly of ferns and fern seeds, with new plants such as conifers and ginkgos becoming important.
Glossopteris, which predominated in southern Pangea, was gradually replaced by the seed fern. Dichroidium as the dry climate increases in the last phase of the period.
© Retallack
– Creative Commons
The weather
When the Permian Period arrived, the planet was still under the effects of the ice age, so large layers still covered the poles. They also engulfed much of Gondwana and the tropics were covered in swampy forests.
As the middle part of the Permian approached, the climate became warm and temperate, because the glaciers were shrinking. At the same time the interior of the continent became drier.
The predominant climate on the Pangea continent was probably arid, although it also had seasonal variations. It could present as wet or dry because there was no moderating effect of ocean water bodies.
The dryness trend persisted to the end, along with warming and cooling variants.
The interior of these regions received rain throughout the year. Little is known about the characteristics of the Panthalassic Ocean itself. There are indications that the climate changed as the ice age receded, causing it to become drier.
Characteristic Permian sites
Due to the conditions described above, this period has few sites that preserve their characteristics. Some exceptional arthropod specimens are known from places such as Kansas and Oklahoma in the United States. However, the Permian is best understood through its vertebrate fossils.
Important areas for Permian vertebrate fossils are the Permian Equatorial Red Beds. They also include the Kazania and Tataria zones in the middle of the Russian shelf, and the Late Permian Karoo system in southern Africa.
The Red Beds are full of pelycosaur fossils. Fins have been found Dimetron, which was a large dominant predator of those environments for 20 million years. In addition, the Russian and South African sites contain the remains of many therapsids. These were creatures that came before the basal synapsids who dominated the earth.
These in turn were replaced by archosaurs during the Early Triassic.
© Prehistoricplanes
– Creative Commons
Vertebrates in the Permian
The great diversity of chondrichthyans that were located near the coasts characterized the Carboniferous, but gradually declined during the Permian. In the oceans the sharks xenacanth They dominated until the Guadalupian, when they were replaced by the hybodonts. Some acanthodii also remained in the Cisuralian.
Lungfish and coelacanths had greater diversity than they do today, but the other sarcopterygian fish were already extinct. The Permian oceans were dominated by a diverse group of spiny-finned fish known as actinoterygii. Most had thick, heavy scales and fairly basic mandibular structures if you look at them in detail. The neopterygians They had derived jaws probably began to appear in the late Lopingienese.
The increasing aridity of the Permian not only affected plants. The tetrapods They suffered when their swamps and ponds shrank and dried up. These surviving forms included temnospoliids with a large head two to three meters long, as well as long-snouted shapes that characterized the archegosaurs. These looked like small crocodiles.
Amniotes were the ones that became the dominant land animals as they adapted to life on land. This happened thanks to dry skin that retains water and development in an amniotic egg. And although there were several different kinds of amniotes, the large and diverse ones that belonged to the Synapsida, which were the ancestors of mammals, stood out.
Evolutionary dynasties of synapsids in the Permian
Pelycosaurs
It included beings with large fins like the Dimetrodon, Edaphosaurus, Ctenospondylus and Secodonotsaurus. They all reached a length of about 3 meters, and had a dorsal sail. These functioned as regulating devices that would warm the animal on cold mornings. It also made them more active and gave them an advantage over their slower relatives who did not possess sails. Its presence was limited to the equatorial tropics.
Dinocephalian
They developed in the middle Permian in the Guadalupian era. The dinocephalians were among the most primitive of the therapsids or mammal-like reptiles. Some grew up to 5 meters long and had heads 50 to 80 centimeters long, full of sharp teeth. They surpassed the previous ones in size and were more metabolically active.
In this dynasty there were anteosaurs primitives who were carnivores, and tapinocephalia They were the size of an ox and were herbivores.
Therapsids
The dinocephalians became extinct…