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The Paleozoic (or Palaeozoic) Era ( ; from the
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
''palaiós'' (), "old" and ''zōḗ'' (), "life", meaning "ancient life") is the earliest of three geologic eras of the
Phanerozoic The Phanerozoic Eon is the current in the , and the one during which abundant and has existed. It covers million years to the present, and it began with the Period when animals first developed hard shells preserved in the fossil record. The ...
Eon. It is the longest of the Phanerozoic eras, lasting from , and is subdivided into six geologic periods (from oldest to youngest): the
Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These perio ...
,
Ordovician The Ordovician ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisions i ...

Ordovician
,
Silurian The Silurian ( ) is a spanning 24.6 million years from the end of the Period, at million years ago (), to the beginning of the Period, Mya. The Silurian is the shortest period of the . As with other periods, the beds that define the per ...
,
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
,
Carboniferous The Carboniferous ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisi ...
, and
Permian The Permian ( ) is a and which spans 47 million years from the end of the Period million years ago (Mya), to the beginning of the Period 251.902 Mya. It is the last period of the Era; the following Triassic Period belongs to the Era. The c ...
. The Paleozoic comes after the
Neoproterozoic The Neoproterozoic Era is the unit of geologic time The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such ob ...
Era of the
Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 541million years ago. It is the most recent part of the Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part ...
Eon and is followed by the
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles and the Age of Conifers, is the second-to-last era An era is a span of time defined for the purposes of chronology or historiography, as in the regnal eras in the history of a given monarchy ...
Era. The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The
Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These perio ...
witnessed the most rapid and widespread diversification of life in Earth's history, known as the Cambrian explosion, in which most modern phyla first appeared.
Arthropod An arthropod (, (gen. ποδός)) is an invertebrate Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This includes all animals apart fr ...
s,
molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are recognized. The number of fossil species is es ...

molluscs
,
fish Fish are , , -bearing animals that lack with . Included in this definition are the living , s, and and as well as various extinct related groups. Around 99% of living fish species are ray-finned fish, belonging to the class , with over 95 ...

fish
,
amphibian Amphibians are ectothermic, tetrapod vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial animal, ter ...
s,
synapsid Synapsids are a group of animals that includes mammals and every animal more closely related to mammals than to the other members of the amniote clade, such as reptiles and birds. Unlike other amniotes, they have a Skull#Fenestrae, temporal fenes ...

synapsid
s and
diapsid Diapsids ("two arches") are a group of amniote tetrapods that developed two holes (temporal fenestra) in each side of their skulls about 300 million years ago during the late Carboniferous period. The diapsids are extremely diverse, and include all ...

diapsid
s all evolved during the Paleozoic. Life began in the ocean but eventually transitioned onto land, and by the late Paleozoic, it was dominated by various forms of organisms. Great
forest A forest is an area of land dominated by tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. In some usages, the definition of a ...

forest
s of primitive plants covered the continents, many of which formed the
coal Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...

coal
beds of
Europe Europe is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered ...

Europe
and eastern
North America North America is a continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continen ...

North America
. Towards the end of the era, large, sophisticated synapsids and diapsids were dominant and the first modern plants (
conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All exta ...

conifers
) appeared. The Paleozoic Era ended with the largest
extinction event An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity Biodiversity is the biological variety and Genetic variability, variability of life, life on Earth. Biodiversity is ...
in the
history of Earth The history of Earth concerns the development of planet A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilibrium, rounded by its own gravity ...
, the
Permian–Triassic extinction event The Permian–Triassic extinction event, also known as the P–Tr extinction, the P–T extinction, the End-Permian Extinction, and colloquially as the Great Dying, formed the boundary between the Permian The Permian ( ) is a geologic period ...
. The effects of this catastrophe were so devastating that it took life on land 30 million years into the Mesozoic Era to recover. Recovery of life in the sea may have been much faster.


Geology

The Paleozoic Era began with the breakup of the supercontinent of
Pannotia Pannotia (from Greek: ''pan- Pan may refer to: Prefix *''Pan-'', a prefix from the Greek language, Greek πᾶν, ''pan'', meaning "all", "of everything", or "involving all members" of a group ** , most but not all using the prefix People * Pan ...

Pannotia
and ended with the assembly of the supercontinent of
Pangaea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology) ...

Pangaea
. The breakup of Pannotia began with the opening of the
Iapetus Ocean upright=1.35, Reconstruction of how the Iapetus Ocean and surrounding continents might have been arranged during the late Ediacaran period (geology), period The Iapetus Ocean (pronounced ) was an ocean that existed in the late Neoproterozoic and e ...
and other Cambrian seas and coincided with a dramatic rise in sea level. Paleoclimatic studies and evidence of
glacier A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abunda ...

glacier
s indicate that
Central Africa Central Africa is a subregion A subregion is a part of a larger region In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhab ...

Central Africa
was most likely in the polar regions during the early Paleozoic. The breakup of Pannotia was followed by the assembly of the huge continent
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (ge ...

Gondwana
(). By mid-Paleozoic, the collision of North America and Europe produced the Acadian-Caledonian uplifts, and a subduction plate uplifted eastern
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Australia
. By the late Paleozoic, continental collisions formed the supercontinent of
Pangaea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology) ...

Pangaea
and created great mountain chains, including the
Appalachians The Appalachian Mountains, often called the Appalachians, are a mountain range, system of mountains in eastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician, Ordovician Period. They once reache ...
,
Ural Mountains The Ural Mountains (; rus, Ура́льские го́ры, r=Uralskiye gory, p=ʊˈralʲskʲɪjə ˈgorɨ; ba, Урал тауҙары, ''Ural tauźarı'') or simply the Urals, are a mountain range that runs approximately from north to south ...
, and mountains of
Tasmania Tasmania (), abbreviated as TAS, is an island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atol ...
.


Periods of the Paleozoic Era

There are six periods in the Paleozoic Era:
Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These perio ...
,
Ordovician The Ordovician ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisions i ...

Ordovician
,
Silurian The Silurian ( ) is a spanning 24.6 million years from the end of the Period, at million years ago (), to the beginning of the Period, Mya. The Silurian is the shortest period of the . As with other periods, the beds that define the per ...
,
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
,
Carboniferous The Carboniferous ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisi ...
(alternatively subdivided into the Mississippian Period and the Pennsylvanian Period), and the
Permian The Permian ( ) is a and which spans 47 million years from the end of the Period million years ago (Mya), to the beginning of the Period 251.902 Mya. It is the last period of the Era; the following Triassic Period belongs to the Era. The c ...
.


Cambrian Period

The Cambrian spanned from 541 to 485 million years ago and is the first period of the Paleozoic Era of the Phanerozoic. The Cambrian marked a boom in evolution in an event known as the Cambrian explosion in which the largest number of creatures evolved in any single period of the history of the Earth. Creatures like
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
evolved, but the most ubiquitous of that period were the armored arthropods, like
trilobite Trilobites (; meaning "three lobes") are a group of marine s that form the Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the of the ( ...

trilobite
s. Almost all marine phyla evolved in this period. During this time, the supercontinent
Pannotia Pannotia (from Greek: ''pan- Pan may refer to: Prefix *''Pan-'', a prefix from the Greek language, Greek πᾶν, ''pan'', meaning "all", "of everything", or "involving all members" of a group ** , most but not all using the prefix People * Pan ...

Pannotia
begins to break up, most of which later became the supercontinent Gondwana.


Ordovician Period

The Ordovician spanned from 485 to 444 million years ago. The Ordovician was a time in Earth's history in which many of the biological classes still prevalent today evolved, such as primitive fish, cephalopods, and coral. The most common forms of life, however, were trilobites, snails and shellfish. The first arthropods went ashore to colonize the empty continent of
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (ge ...

Gondwana
. By the end of the Ordovician, Gondwana was at the south pole, early North America had collided with Europe, closing the Atlantic Ocean. Glaciation of Africa resulted in a major drop in sea level, killing off all life that had established along coastal Gondwana. Glaciation may have caused the
Ordovician–Silurian extinction events The Ordovician–Silurian extinction events, also known as the Late Ordovician mass extinction, are collectively the second-largest of the five major extinction events in Earth's history in terms of percentage of Genus, genera that became extinct. ...
, in which 60% of marine invertebrates and 25% of families became extinct, and is considered the first mass extinction event and the second deadliest.


Silurian Period

The Silurian spanned from 444 to 419 million years ago. The Silurian saw the rejuvenation of life as the Earth recovered from the previous glaciation. This period saw the mass evolution of fish, as jawless fish became more numerous, jawed fish evolved, and the first freshwater fish evolved, though arthropods, such as , were still
apex predator The great white shark (bottom) was originally considered the apex predator of the ocean; however, the killer whale (top) has proven to be a predator of the shark. An apex predator, also known as an alpha predator or top predator, is a predator ...
s. Fully terrestrial life evolved, including early arachnids, fungi, and centipedes. The evolution of
vascular plants Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from the Greek ''trācheia''), form a large group of plants ( 300,000 accepted known species) that are defined as land plants with lignified tissue ...
(''
Cooksonia ''Cooksonia'' is an extinct group of primitive land plant The Embryophyta (), or land plants, are the most familiar group of green plant Plants are predominantly photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Histor ...

Cooksonia
'') allowed plants to gain a foothold on land. These early plants were the forerunners of all plant life on land. During this time, there were four continents: Gondwana (Africa, South America, Australia, Antarctica, Siberia), Laurentia (North America), Baltica (Northern Europe), and Avalonia (Western Europe). The recent rise in sea levels allowed many new species to thrive in water.


Devonian Period

The Devonian spanned from 419 to 359 million years ago. Also known as "The Age of the Fish", the Devonian featured a huge diversification of fish, including armored fish like ''
Dunkleosteus ''Dunkleosteus'' is an Extinction (biology), extinct genus of arthrodire placoderm fish that existed during the Late Devonian period, about 358–382 million years ago. The name ''Dunkleosteus'' combines the Greek language, Greek , ''osteon'', mean ...

Dunkleosteus
'' and lobe-finned fish which eventually evolved into the first
tetrapod Tetrapods (; ) are four-limbed animals constituting the superclass Tetrapoda (). It includes extant Extant is the opposite of the word extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a sp ...
s. On land, plant groups diversified incredibly in an event known as the Devonian explosion when plants made lignin allowing taller growth and vascular tissue: the first trees evolved, as well as seeds. This event also diversified arthropod life, by providing them new habitats. The first amphibians also evolved, and the fish were now at the top of the food chain. Near the end of the Devonian, 70% of all species became extinct in an event known as the
Late Devonian extinction The Late Devonian extinction was one of five major extinction event An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a shar ...
, which was the Earth's second mass extinction event.


Carboniferous Period

The Carboniferous spanned from 359 to 299 million years ago. During this time, average global temperatures were exceedingly high; the early Carboniferous averaged at about 20 degrees Celsius (but cooled to 10 °C during the Middle Carboniferous). Tropical swamps dominated the Earth, and the lignin stiffened trees grew to greater heights and number. As the bacteria and fungi capable of eating the lignin had not yet evolved, their remains were left buried, which created much of the carbon that became the coal deposits of today (hence the name "Carboniferous"). Perhaps the most important evolutionary development of the time was the evolution of amniotic eggs, which allowed amphibians to move farther inland and remain the dominant vertebrates for the duration of this period. Also, the first reptiles and
synapsid Synapsids are a group of animals that includes mammals and every animal more closely related to mammals than to the other members of the amniote clade, such as reptiles and birds. Unlike other amniotes, they have a Skull#Fenestrae, temporal fenes ...

synapsid
s evolved in the swamps. Throughout the Carboniferous, there was a cooling trend, which led to the Permo-Carboniferous glaciation or the
Carboniferous Rainforest Collapse The Carboniferous rainforest collapse (CRC) was a minor extinction event that occurred around 305 million years ago in the Carboniferous period. It altered the vast coal forests that covered the equatorial region of Euramerica (Europe and America). ...
.
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (ge ...

Gondwana
was glaciated as much of it was situated around the south pole.


Permian Period

The Permian spanned from 299 to 252 million years ago and was the last period of the Paleozoic Era. At the beginning of this period, all continents joined together to form the supercontinent
Pangaea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology) ...

Pangaea
, which was encircled by one ocean called
Panthalassa Panthalassa, also known as the Panthalassic Ocean or Panthalassan Ocean (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located i ...
. The land mass was very dry during this time, with harsh seasons, as the climate of the interior of Pangaea was not regulated by large bodies of water.
Diapsid Diapsids ("two arches") are a group of amniote tetrapods that developed two holes (temporal fenestra) in each side of their skulls about 300 million years ago during the late Carboniferous period. The diapsids are extremely diverse, and include all ...

Diapsid
s and
synapsid Synapsids are a group of animals that includes mammals and every animal more closely related to mammals than to the other members of the amniote clade, such as reptiles and birds. Unlike other amniotes, they have a Skull#Fenestrae, temporal fenes ...

synapsid
s flourished in the new dry climate. Creatures such as ''
Dimetrodon ''Dimetrodon'' ( or , meaning "two measures of teeth") is an extinct genus of non-mammalian synapsid that lived during the Permian#anchor 3, Cisuralian (Early Permian), around 295–272 million years ago (Ma). It is a member of the family Sp ...

Dimetrodon
'' and ''
Edaphosaurus ''Edaphosaurus'' (, meaning "pavement lizard" for dense clusters of teeth) is a genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the principles t ...

Edaphosaurus
'' ruled the new continent. The first conifers evolved, and dominated the terrestrial landscape. Near the end of the Permian, however, Pangaea grew drier. The interior was desert, and new taxa such as ''
Scutosaurus ''Scutosaurus'' ("Shield lizard") was a genus of parareptiles. It was an armor-covered pareiasaur that lived around 265–254 million years ago in Russia, in the later Permian period. Its genus name refers to large plates of armor scattered across ...

Scutosaurus
'' and Gorgonopsids filled it. Eventually they disappeared, along with 95% of all life on Earth, in a cataclysm known as " The Great Dying", the third and most severe mass extinction.


Climate

The early
Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These perio ...
climate was probably moderate at first, becoming warmer over the course of the Cambrian, as the second-greatest sustained
sea level rise Tide gauge measurements show that the current global sea level rise began at the start of the 20th century. Between 1900 and 2017, the globally averaged sea level Mean sea level (MSL) (often shortened to sea level) is an average In colloqu ...

sea level rise
in the
Phanerozoic The Phanerozoic Eon is the current in the , and the one during which abundant and has existed. It covers million years to the present, and it began with the Period when animals first developed hard shells preserved in the fossil record. The ...
got underway. However, as if to offset this trend,
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (ge ...

Gondwana
moved south, so that, in Ordovician time, most of West Gondwana (Africa and South America) lay directly over the
South Pole The South Pole, also known as the Geographic South Pole, Terrestrial South Pole or 90th Parallel South, is one of the where intersects its surface. It is the southernmost point on Earth and lies on the of Earth from the . Situated on the ...
. The early Paleozoic climate was also strongly zonal, with the result that the "climate", in an abstract sense, became warmer, but the living space of most organisms of the time—the continental shelf marine environment—became steadily colder. However,
Baltica Baltica is a paleocontinent A paleocontinent or palaeocontinent is a distinct area of continental crust 350px, The thickness of Crust (geology)#Earth's crust, Earth's crust (km) Continental crust is the layer of Igneous rock, igneous, Sedim ...
(Northern Europe and Russia) and
Laurentia Image:North america craton nps.gif, upright=1.4, Laurentia, also called the North American craton Laurentia or the North American Craton is a large continental craton that forms the Geology of North America, ancient geological core of North Ameri ...
(eastern North America and Greenland) remained in the tropical zone, while China and Australia lay in waters which were at least temperate. The early Paleozoic ended, rather abruptly, with the short, but apparently severe, late Ordovician ice age. This cold spell caused the second-greatest mass extinction of Phanerozoic time. Over time, the warmer weather moved into the Paleozoic Era. The
Ordovician The Ordovician ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisions i ...

Ordovician
and
Silurian The Silurian ( ) is a spanning 24.6 million years from the end of the Period, at million years ago (), to the beginning of the Period, Mya. The Silurian is the shortest period of the . As with other periods, the beds that define the per ...
were warm greenhouse periods, with the highest sea levels of the Paleozoic (200 m above today's); the warm climate was interrupted only by a cool period, the Early Palaeozoic Icehouse, culminating in the
Hirnantian The Hirnantian is the final internationally recognized stage of the Ordovician Period The Ordovician ( ) is a geologic period and system A system is a group of Interaction, interacting or interrelated elements that act according to a set of r ...
glaciation, at the end of the Ordovician. The middle Paleozoic was a time of considerable stability. Sea levels had dropped coincident with the ice age, but slowly recovered over the course of the
Silurian The Silurian ( ) is a spanning 24.6 million years from the end of the Period, at million years ago (), to the beginning of the Period, Mya. The Silurian is the shortest period of the . As with other periods, the beds that define the per ...
and
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
. The slow merger of
Baltica Baltica is a paleocontinent A paleocontinent or palaeocontinent is a distinct area of continental crust 350px, The thickness of Crust (geology)#Earth's crust, Earth's crust (km) Continental crust is the layer of Igneous rock, igneous, Sedim ...
and
Laurentia Image:North america craton nps.gif, upright=1.4, Laurentia, also called the North American craton Laurentia or the North American Craton is a large continental craton that forms the Geology of North America, ancient geological core of North Ameri ...
, and the northward movement of bits and pieces of Gondwana created numerous new regions of relatively warm, shallow sea floor. As plants took hold on the continental margins,
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
levels increased and
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
dropped, although much less dramatically. The north–south temperature gradient also seems to have moderated, or metazoan life simply became hardier, or both. At any event, the far southern continental margins of
Antarctica Antarctica ( or ) is Earth's southernmost continent. It contains the geographic South Pole and is situated in the Antarctic region of the Southern Hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Oc ...

Antarctica
and West
Gondwana Gondwana () or Gondwanaland was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (ge ...

Gondwana
became increasingly less barren. The Devonian ended with a series of turnover pulses which killed off much of middle Paleozoic vertebrate life, without noticeably reducing species diversity overall. There are many unanswered questions about the late Paleozoic. The Mississippian (early Carboniferous Period) began with a spike in atmospheric oxygen, while carbon dioxide plummeted to new lows. This destabilized the climate and led to one, and perhaps two, ice ages during the
Carboniferous The Carboniferous ( ) is a geologic period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These periods form elements of a hierarchy of divisi ...
. These were far more severe than the brief Late Ordovician ice age; but, this time, the effects on world biota were inconsequential. By the
Cisuralian The Cisuralian is the first series/ epoch of the Permian. The Cisuralian was preceded by the Pennsylvanian and followed by the Guadalupian. The Cisuralian Epoch is named after the western slopes of the Ural Mountains in Russia and Kazakhstan ...
Epoch, both oxygen and carbon dioxide had recovered to more normal levels. On the other hand, the assembly of
Pangaea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology) ...

Pangaea
created huge arid inland areas subject to temperature extremes. The
Lopingian The Lopingian is the uppermost series/last epoch of the Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous period million years ago (Mya), to the beginning of ...
Epoch is associated with falling sea levels, increased carbon dioxide and general climatic deterioration, culminating in the devastation of the
Permian extinction The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous The Carboniferous ( ) is a geologic period and system A system is a group of Interaction, interacting or interrela ...
.


Flora

While macroscopic plant life appeared early in the Paleozoic Era and possibly late in the Neoproterozoic Era of the earlier eon, plants mostly remained aquatic until the
Silurian The Silurian ( ) is a spanning 24.6 million years from the end of the Period, at million years ago (), to the beginning of the Period, Mya. The Silurian is the shortest period of the . As with other periods, the beds that define the per ...
Period, about 420 million years ago, when they began to transition onto dry land. Terrestrial flora reached its climax in the Carboniferous, when towering
lycopsid Lycopodiopsida is a class of herbaceous vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are called clubmosses, firmosses and quillworts. They have dichotomously branching stems be ...
rainforests dominated the tropical belt of
Euramerica Laurasia (), a portmanteau for Laurentia and Asia, was the more northern of two large landmasses (the other being Gondwana) that formed part of the Pangaea supercontinent from around (Mya (unit), Mya). It separated from Gondwana (beginning in t ...
. Climate change caused the
Carboniferous Rainforest Collapse The Carboniferous rainforest collapse (CRC) was a minor extinction event that occurred around 305 million years ago in the Carboniferous period. It altered the vast coal forests that covered the equatorial region of Euramerica (Europe and America). ...
which fragmented this habitat, diminishing the diversity of plant life in the late Carboniferous and Permian periods.


Fauna

A noteworthy feature of Paleozoic life is the sudden appearance of nearly all of the
invertebrate Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This includes all animals apart from the chordata, chordate subphylum vertebrate, Vertebra ...
animal phyla in great abundance at the beginning of the Cambrian. The first vertebrates appeared in the form of primitive fish, which greatly diversified in the Silurian and Devonian Periods. The first animals to venture onto dry land were the arthropods. Some fish had lungs, and powerful bony fins that in the late Devonian, 367.5 million years ago, allowed them to crawl onto land. The bones in their fins eventually evolved into legs and they became the first
tetrapods Tetrapods (; ) are four-limbed animals constituting the superclass Tetrapoda (). It includes extant Extant is the opposite of the word extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a sp ...

tetrapods
, , and began to develop lungs. Amphibians were the dominant tetrapods until the mid-Carboniferous, when climate change greatly reduced their diversity. Later, reptiles prospered and continued to increase in number and variety by the late Permian period.


See also

* * * * *


References


Further reading

* ''British Palaeozoic Fossils'', 1975, The Natural History Museum, London. *


External links


60+ images of Paleozoic Foraminifera


{{Authority control Geological eras