The Permian period was named by the geologist Murchison in 1841 after the ancient kingdom of Permia and the present city of Perm (near the Ural Mountains). The Permian period came to a close with the largest extinction event in the history of life where approximately 95% of all species and about 60% of the genera died out. The cause of the Permian extinction is not completely understood but it is theorized that it might have been global cooling, volcanic eruptions, an extraterrestrial impact (meteor), and/or a decrease in the continental shelf area during the formation of Pangaea.
Tectonics and Paleoclimate
During the Permian all the world's land masses joined together into a single super continent called Pangea. The collision between Laurasia, Siberia-Kazakhstania, and China finalized the assembly of Pangaea by end of Permian. This was the first time since the late Proterozoic super continent of Rodinia that such a landmass had formed. There was a correspondingly large, single ocean called Panthalassa. Pangea was shaped like a fat letter “C” with the opening on the east. The body of water enclosed by the “C” constituted a smaller sea known as Tethys. As the Permian opened, the Earth was still in the grip of an ice age, so the Polar Regions were covered with deep layers of ice. Glaciers continued to cover much of Gondwanaland as they had during the late Carboniferous. The tropical areas were covered in swampy forests. Towards the middle of the period, the climate became warmer and milder, the glaciers receded, and the continental interiors became drier. Much of the interior of Pangea was probably arid with great seasonal wet and dry season fluctuations because of the lack of the moderating effect of nearby bodies of water. This drying tendency continued through to the late Permian in conjunction with alternating warming and cooling periods.
The early Permian flora was abundant in both the polar tundra regions and the warm, wet tropical swamp forest ecosystems. However, the drying climate during the mid Permian spelled death for the mighty swamp forests. Water loving plants like Lycopods and Sphenopsids were greatly reduced in size becoming mere shrubs. Plant life consisted mainly of ferns and seed-ferns with new plants such as conifers and ginkgos coming into prominence. The Glossopteris was the predominate flora in the southern portion of Pangaea (a.k.a. Gondwanaland) and was gradually replaced by the seed-fern Dicroidium as the climate continued to dry out in the Late Permian.
The warm shallow oceans swarmed with many kinds of life including sedentary organisms like stromatolites, algae, foraminifers, sponges, corals, bryozoa, and brachiopods that formed great reefs which in turn provided homes and shelter for active animals like ammonoids, nautiloids, gastropods, and ancient fish.
The drying climate during the mid Permian also negatively affected the fauna of the period as swamps and pools dried out many forms of tetrapodomorphs vanished. Those that survived (e.g.., temnospondyls and archegosaurs) found their world dominated by reptiles, the largest and most diverse being the lineage known as Synapsida (Theropsida) which are considered to be mammalian ancestors. There were distinct evolutionary stages in the reptilia during the Permian period characterized as follows:
- The first was the “pelycosaur dynasty” of the early Permian that featured large finbacks such as Dimetrodon, Edaphosaurus, Ctenospondylus, and Secodontosaurs as well similar animals that lacked a "back sail". The large dorsal sails are hypothesized to be thermoregulatory devices that would heat up the animal in the cold morning making it more active thus giving it an advantage over it's more sluggish sail-less relatives. These animals were limited to the equatorial tropics.
- The second stage was the “Dinocephalian dynasty” of the middle Permian which featured the therapsids or "mammal-like reptiles" some of which grew huge in size with long heads full of wicked teeth. These creatures succeeded the Pelycosaurs, being both larger in size and more metabolically active. In addition, this dynasty included several different types of primitive carnivorous anteosaurs, the herbivorous tapinocephalia and pareiasaurs, and many types of small lizard-like reptiles.
- The third stage occurred at the end of the Permian when the Dinocephalians all suddenly died out perhaps due to unusual climatic factors. The Therapsids that followed were smaller but more mammal-like. Some may even have had fur and were perhaps warm-blood. These included the large gorgonopsians, the small to medium-sized Therocephalia, and the herbivorous dicynodonts.
Meteorite Impacts on Earth
I included a list of meteorite impacts relevant to this time period as a point of reference since many of the explanations for mass extinctions throughout Earth’s history include meteorite impact(s) as a possible cause. The meteorite impact information below was obtained from the ‘Earth Impact Database’ maintained by the Planetary and Space Science Centre, University of New Brunswick, Fredericton, New Brunswick, Canada ( www.passc.net/EarthImpactDatabase).