Permian period spans from 299 to 251 million years ago.
This geologic period was named after province of Perm in
U.S.S.R. where rocks of this age were first studied (USGS).
Sir Roderick Impey Murchison (1792-1871) a Scottish geologist
named the Permian in 1841.
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.
Producers & Reefs
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).
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.
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 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.
(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).
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
1988, p. 48).
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.
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
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.
diversify into new groups. Pelycosaurs continued their
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).
undergo a great adaptive radiation during the Permian period
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
of insect species at this time; today more than 80% of insect
species undergo complete metamorphosis (Rich, 1996, pp. 234-235).
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)
Medullosa also accounted for a good percentage of
the plant life while the role of lycopsids decreased. A particular
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
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).
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).
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).
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.
plants experienced their greatest losses during the Permian
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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