The transition into the Permian was relatively uneventful, but a cooling and drying trend during the Permian would affect the distribution and diversity of organisms. The Permian would end with an abrupt warming trend and the largest mass extinction.

Primary Producers & Reefs

The dominant primary producers in the oceans continue to be cyanobacteria, green and red algae (Knoll, Summons, Waldbauer, and Zumberge, 2007, p. 148). Calcareous algae and calcareous sponges were the most important reef builders during the Permian (Stanley, 1987, p. 101). Stromatolites, corals, bryozoans, and brachiopods were also a part of reef ecosystems. In many Permian reef systems the problematic Archaeolithoporella was important in binding reefs with carbonates (Webb, 2001, p. 176) and (Grimm, 2008, slide 16).

Marine Invertebrates

Invertebrates such as sponges, corals, bryozoans, and brachiopods are important participants in reef communities. Ammonoids and nautiloids continued to be important invertebrate predators among these reefs (Kazlez, 2002, Permian Page). Crinoids and fusulinids were still abundant. Trilobites were on a decline and go extinct at the end of the Permian.

Fish

Jawless fish (Agnatha) continue to decline. Cartilaginous (Chondrichthyes) fish are numerous in both marine and freshwater environments. Spiny sharks (Acanthodii) decline and go extinct at the end of the Permian. Primitive ray-finned fish (Osteichthyes) are numerous in both marine and freshwater environments. Lobe-finned fish and lungfish (Osteichthyes) are on the decline. Rhipidistians, lobe-finned fish that are the ancestors of land vertebrates go extinct during the Permian (Dixon, 1988, p. 44).

Amphibians

Paleozoic amphibians continue their adaptive radiation in the Permian, reaching their greatest diversity. Temnospondyls continued to flourish. Eryops and Edops from the Lower Permian of Texas were up to 2 meters in length, making them some of the largest predators outside Dimetrodon. Eryops and Edops probably lived their lives like crocodiles lurking in the streams and moving into and out of water.

Lepospondyls (Superorder Lepospondyli) are early amphibians that range from the Carboniferous to the Permian. Microsaurs and nectrideans are the best-known lepospondyls. Microsaurs (Order Microsauria) were the largest group of lepospondyls and had a body form reminiscent of salamanders or lizards. Most microsaurs were terrestrial feeding on arthropods although, some became secondarily adapted to aquatic environments. The nectrideans (Order Nectridia) were aquatic organisms that had newt-like bodies with long tails. Their heads were equipped with horn-like structures that grew as the animal aged. Diplocaulus is a well-known nectridean with a “boomerang” shaped skull. Biomechanical studies on models of a Diplocaulus head provide evidence that it acted as a hydrofoil, providing lift. Diplocaulus swam in streams and lakes feeding on fish. Diplocaulus and its close relative Diploceraspis are known from teh Upper Carboniferous and Lower Permian of midwestern USA (Benson, 2005, pp. 89-90).

It is interesting to note that early amphibians and reptiles are found almost exclusively on the Euramerican continent. After Asia and Gondwanaland merge with Euramerica, during the mid-Permian, amphibians and reptiles spread worldwide (Dixon, 1988, p. 48).

Reptile-Like Amphibians

Diadectimorphs are reptile-like amphibians that are very close to the origin of amniotes. Diadectes from the Early Permian of Western USA and Germany is a massively built reptiliomorph that represents one of the first terrestrial vertebrate herbivores. Diadectes had a reptile-like skeleton with massive limb girdles, short limbs, and heavy vertebrae. At up to 3 meters in length, Diadectes represents one of the first fully terrestrial tetrapods to attain a large size. Diadectes skull was amphibian-like. The front of the jaw had eight peg-like incisors for clipping vegetation and rows of blunt cheek teeth for grinding (Benton, 2005, p. 101). Diadectes also possessed an otic notch, like other Paleozoic amphibians. The tympanum of Diadectes was ossified. Reptile-like amphibians would go extinct in the Early Triassic, but one of their evolutionary lines, the amniote clade, would live on. Other reptile-like mammal groups continued to do well in the Permian including the anthracosaurs and seymouriamorphs.

Reptiles

Reptile groups continued to diversify during the Permian. Several new families of anapsid type reptiles appear in the Permian, we will mention just two groups. Members of the order Mesosuria represent the first reptiles to adapt to an aquatic existence, though their ancestors were terrestrial. This order of reptiles appears and goes extinct during the Permian. Mesosaurus was a freshwater species in this group, which acted as a key piece of biological evidence in favor of Alfred Wegener’s theory of Continental Drift and the existence of Pangea. Mesosaurus fossils are found in both South America and South Africa. This animal could not have crossed the Atlantic Ocean thus the continents must have been joined when Mesosaurs was alive (Dixon, 1988, p.65). Pareiasaurs (family Pareiasauridae) were the largest primitive retiles. Pareiasaurs were large herbivores that had their legs placed underneath their body, so they could walk more upright. Pareiasaurs make their appearance during the Permian, but go extinct by the end of the same period. Pareiasaurus and Scutosaurus were typical members of the family, heavily-built herbivores reaching lengths of 8ft.

Diapsids continue to evolve and diversify. Lizards and snakes are the most successful order of reptiles today (Squamata). The first lizard, representing the order Squamata, appears in the late Permian. Another important diapsid group, which makes its first appearance in the late Permian, is the archosaurs (Archosauromorpha), which would eventually include the ruling lizards (dinosaurs, pterosaurs, and crocodiles). Archosaur legs were placed more directly under the body than other lizards, an important terrestrial adaptation. The first archosauromorph was Protorosaurus (Dixon, 1988, pp. 88-89).

Protomammals

Synapsids diversify into new groups. Pelycosaurs continued their adaptive radiation. Dimetrodon may be the most well known predator from the Permian. Dimetrodon’s large sail-like structure may have helped the animal to thermoregulate. Although the first pelycosaurs were carnivorous, herbivorous forms evolved in the late Carboniferous and diversified during the Permian. A new synapsid group, the therapsids (reptile-like mammals or protomammals), would appear in the Permian. Two important groups of therapsids appear in the late Permian. The dicynodonts were the most successful plant-eating group of therapsids. Cynodonts were the longest-lived group of therapsids and gave rise to the mammals (Dixon, 1988, pp188-193). Synapsids during the Permian were looking more like mammals. Teeth became more differentiated and the crouching posture changed to a more upright stance. One wonders if the therapsids of the late Permian were warm-blooded or endothermic (Stanley, 1987, p. 95).

Insects

Insects undergo a great adaptive radiation during the Permian period and many first appearances occur. We will mention a few examples. Among the fixed winged insects (Paleoptera) dragonflies and damselflies (Odonota) make their first appearance (the dragonfly-like organisms of the Carboniferous belong to the extinct order Protodonata). Among insects with folded wings (Neoptera) stoneflys (Plecoptera), Thrips (Thysanoptera), and true bugs (Hemiptera) make their first appearance. Insects that undergo complete metamorphosis (endopterygote Neoptera) make their first appearance during the Permian, although it is speculated that they evolved sometime during the Carboniferous. Among the insects with complete metamorphosis that make their first appearance during the Permian are scorpion flies (Mecoptera), lacewings (Neuroptera), grasshoppers (Orthoptera) and beetles (Coleoptera) (Carpenter & Burnham, 1985, pp.306-308: Grimaldi & Engel, 2005, p. 208). Insects with complete metamorphosis accounted for a very small percentage of insect species at this time; today more than 80% of insect species undergo complete metamorphosis (Rich, 1996, pp. 234-235).

Plants

At the beginning of the Permian, the clubmosses, horsetails, ferns, seed ferns, and cordaites, which had dominated the Carboniferous, continued to flourish. Indeed half of all known plant species at this time were clubmosses, which today account for less than 1 percent (Kenrick & Davis, 2004, p. 141). As the Permian progressed swamp forests would contract and eventually be replaced by new floras. In the early Permian these changes occurred in North America and Europe. In China these changes would not occur until the late Permian. In many Permian forests the canopy became dominated by cordaites, tree ferns like Psaronius and horsetails like Calamites. Seed ferns (Pteridosperms) like Medullosa also accounted for a good percentage of the plant life while the role of lycopsids decreased. A particular order of seed ferns, Glossopteridales, is of particular interest. Glossopteris was a seed-bearing shrub or tree. Glossopteris reached heights of 4 m. The trunk was made of araucariod-like wood; leaves were tongue-shaped and bore slender stalks with clusters of organs containing seeds and pollen. In the early Permian Glossopteris appears in Gondwana, but spreads across Pangea by the end of the Permian. Glossopteris fossils are found in South America, Africa, India, Antarctica, and Australia. The distribution of Glossopteris was a key piece of biological evidence that supported Continental Drift (Kenrick & Davis, 2004, pp. 154-157). Conifers became more diverse and more abundant towards the end of the Permian. In some locations Dadoxylon, a type of Araucaria, are among the largest and most numerous trunks (Dernbach & Tidwell, 2002, p. 119). Ginkgophytes make their first undisputed appearance in the Permian; however, the genus Ginkgo does not appear until the Mesozoic (Taylor, Taylor, and Krings, 2009, p. 744).

Plant life can be divided into geologic eras that differ from that of the familiar animal eras of Paleozoic (ancient life), Mesozoic (middle life), and Cenozoic (recent life). Plant eras include the Paleophytic (ancient plant--Silurian-Permian), Mesophytic (middle plant--Triassic-Early Cretaceous), and Cenophytic (recent plant--Late Cretaceous to present). Clubmosses, horsetails, and ferns, which all reproduce with spores constituted the dominant floras of the Paleophytic. The conifers, which reproduce using seeds, would be the dominant floras of the Mesophytic (Kenrick & Davis, 2004, p. 143).

The Greatest Mass Extinction

The Permian period ended with the largest recorded mass extinction that hit both aquatic and terrestrial environments. It is estimated that 75 to 90 percent of all living species became extinct over a period of 10 million years (Stanley, 1987, pp. 96-97). Sixty percent of marine families became extinct (Palmer, 1999, p. 90). In the marine realm crinoids, brachiopods, bryozoans, and ammonoids were hit hard. Fusulinids, trilobites, graptolites, blastoids, rugose corals, tabulate corals, and eurypterids met with extinction. Among the fish Acanthodians and Placoderms became extinct. Rhipidistians, lobe-finned fish (Osteichthyes) that are the ancestors of land vertebrates also went extinct. Extinction in the marine realm marked a change from a Paleozoic dominated fauna composed of crinoid, coral, bryozoan, and brachiopods to a modern fauna dominated by bivalves, gastropods, and echinoids (Prothero, 2004, p. 86).

Two-thirds of the amphibian and reptile families met with extinction. The larger terrestrial vertebrates did not fare as well. Thirty-three percent of amphibian families went extinct at the end of the Permian (Palmer, 1999, p. 90). Among the amphibians some labyrinthodonts would survive into the Triassic. Lepospondyls (Lepospondyli) amphibians went extinct by the end of the Permian. All but one group of anapsid type reptiles died out. The fossil evidence for diapsid reptiles is sparse during the mid Permian, although many new groups make their first appearance during the late Permian. The most primitive groups of diapsids went extinct at the end of the Permian (Dixon, 1988, p. 84). The first synapsids were the pelycosaurs, which made up 70% of the vertebrate terrestrial fauna in the early Permian. During the middle Permian another group of synapsids, the therapsid, would evolve and displace the pelycosaurs. Pelycosaurs died out in the middle Permian. Therapsids would loose 21 families at the end of the Permian (Palmer, 1999, p. 90).

For the first time insects suffered a mass extinction. Many of the primitive orders of insects went extinct during the Permian event. Among the fixed-winged insects (Paleoptera) the following orders went extinct: Palaeodictyoptera, Megasecoptera, Diaphanopterodea, and Protodonata. Among the folded-winded insects with incomplete metamorphosis (exopterygota Neoptera) the following orders went extinct: Protorthoptera, Caloneurodea, Protelytroptera, and Miomoptera) (Carpenter & Burnham, 1985, p. 302). Insect fossils found after the Permian belong mostly to modern insect groups.

Globally, plants experienced their greatest losses during the Permian extinction. Only 9 out of 22 known families survived into the Triassic (Cleal & Thomas, 2009, p. 209). As noted earlier, the swamp forests of the Carboniferous contracted during the Permian. As the clubmosses waned, ferns and primitive conifers expanded to take their place. The change from Paleophytic to Mesophytic flora occurred over a period of 25 million years. Tropical plant ecosystems suffered major disruptions with some extinction at the end of the Permian period. Cordaites went extinct as well as the seed fern Glossopteris. The dominant conifer families (Walchiaceae, Ullmanniaceae, and Majonicaceae) of the time went extinct. For a geologically short time, woody coniferous forests were replaced by herbaceous species of clubmosses and quillworts (4-5 million years). In the Triassic, woody coniferous forests of a different type would be reestablished (Kenrick & Davis, 2004, p. 154).

Uranium-lead zircon geochronology has been used to date ash layers, associated with the Siberian Traps, at the Permian-Triassic boundary in Southern China. The results establish a date of 251 Ma (Wignall, 2001, p. 8). The extinction interval is thought to be very short on the order of 165,000 years or less (Prothero, 2004, p. 87). What caused the "mother of all extinctions?"

An increase in dune deposits, evaporite salts, and a lack of coal forming swamps may indicate arid conditions in some terrestrial environments. There is evidence of a marine regression, which would reduce habitat in shallow marine environments. A rapid warming trend occurred at the end of the Permian. An increase in O-16 over O-18 in the calcite skeletons of marine organisms indicates global temperatures may have increased by as much as 6 degrees Celsius. An increase in C-12 found in terrestrial and marine sections could be an indication of increased volcanic activity and massive death in the marine and terrestrial realms (Benton, 2003, p. 38). Like the Ordovician and Devonian events a reduction in the formation of marine limestone and reef building occurred after the Permian extinction. Layers containing abundant pyrite above the limestone layers indicate a low oxygen environment.

Onset of flood basalts making up the Siberian Traps occur at the Permian-Triassic boundary. This LIP formed in northern Asia and may have been the source of carbon dioxide that started a global warming event. As the climate warmed methane may have been released from methane clathrates accelerating the warming event. The release of these gasses into the atmosphere is called the "big belch" and may have increased temperatures and lowered oxygen levels (Cleal & Thomas, 2009, p. 209). Climate change may have also altered oceanic circulation in such a way as to bring stagnant deep water rich in carbon dioxide and hydrogen sulfide to the surface. The Permian crises would usher in a new era represented by different flora and fauna evolved from the small percentage of survivors who were, at first, cosmopolitan in their distribution.

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