Paleozoic Era 2

1. Paleozoic Era
In geologic time , the Paleozoic Era, the first era in the
Phanerozoic Eon , covers the time between roughly 544
million years ago (mya) and until 245 mya. The Paleozoic or
Palaeozoic Era (from the Greek palaios, "old" and zoe, "life",
meaning "ancient life") is the earliest of three geologic eras of
the Phanerozoic Eon.
The Paleozoic Era spans six geologic time periods including
the Cambrian Period (544 to 500 mya); Ordovician Period
(500 mya to 440 mya); Silurian (440 mya to 410 mya);
Devonian (410 mya to 360 mya); and the Carboniferous Period
(360 mya to 286 mya) (in many modern geological texts,
especially those in the United States, the time of
Carboniferous Period is covered by two alternate geologic
periods, the Mississippian Period [360 mya to 325 mya] and
the Pennsylvanian Period [325 mya to 286 mya]. The final
geologic time period in the Paleozoic Era is the Permian
Period (286 mya to 245 mya).
The onset of the Paleozoic Era is marked by the "Cambrian
explosion," the sudden appearance of numerous fossils .

3. • Tectonics
• Geologically, the Paleozoic
starts shortly after the
breakup of a supercontinent
called Pannotia and at the
end of a global ice age. (See
Varanger glaciation and
Snowball Earth). Throughout
the early Paleozoic, the
Earth's landmass was broken
up into a substantial number
of relatively small continents.
Toward the end of the era,
the continents gathered
together into a
supercontinent called
Pangaea, which included
most of the Earth's land area.

4. • Paleoclimatic studies and evidence of glaciers indicate
that central Africa was most likely in the polar regions
during the early Paleozoic.
• During the early Paleozoic, the huge continent
Gondwanaland had either formed or was forming.
• By mid-Paleozoic, the collision of North America and
Europe produced the Acadian-Caledonian uplifts, and
a subduction plate uplifted eastern Australia.
• By the late Paleozoic, continental collisions formed the
supercontinent Pangaea and resulted in some of the
great mountain chains, including the Appalachians,
Urals, and Tasmans.

5. • Avalon: A micro-continent located between
North America and Africa. When these two
landmasses collided, Avalon became part of
the eastern margin of North America in a
process known as the Acadian Orogeny, the
formation of the Acadian Mountains.
• Iapetus Ocean: An ancient southern
hemisphere sea located between Laurentia
(now N. America) and Baltica (now part of
Russia). As Laurentia, Baltica, and Africa
gradually collided the Iapetus slowly
disappeared.

9. • Late Paleozoic Tectonic Setting
• The supercontinent Pangea (from the Greek, meaning "all
land") was gradually assembled as the continents collided
during the Late Paleozoic.
• The larger continents (such as North America) grew by the
addition of island arcs and microcontinents around their
edges. Continental collisions caused several orogenies or
mountain-building events in eastern North America.
• Acadian orogeny and Caledonian orogeny
Middle Silurian to middle Devonian.
Laurentia (North America) and Baltica (Europe) collide to
form Laurasia, and a volcanic island arc (Avalon terrane
or Carolina terrane) collides with eastern North America.
• Late Carboniferous
Gondwana (the southern continents, Africa, South
America, India, Australia, Antarctica) and Laurasia collide.
Southern Appalachian mountains form as Laurasia collides
with northwestern Africa (part of Gondwana).

11. • Animal Life
• Paleozoic life is the sudden appearance of nearly all of
the invertebrate animal phyla in great abundance at the
beginning of the Cambrian. A few primitive fishlike
invertebrates, and then vertebrates, appeared in the
Cambrian and Ordovician, scorpions in the Silurian
period, land invertebrates and amphibians in the
Devonian, land reptiles in the Carboniferous, and marine
reptiles in the Permian.
• Amphibians were the dominant vertebrates until the mid
Carboniferous, then climate change greatly reduced their
diversity; meanwhile reptiles prospered and continued to
increase in number and variety by the late Permian.

12. • Plant Life
• Plant life of the Paleozoic era reached its
climax in the Carboniferous, when
towering lycopsid rainforests dominated
the tropical belt of Euramerica. Climate
change caused the
Carboniferous Rainforest Collapse which
fragmented this habitat, diminishing the
diversity of plant life in the late
Carboniferous and Permian.

13. • Climate
• The Ordovician and Silurian periods 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 ~30 Ma cool period,
the Early Palaeozoic Icehouse,
culminating in the Hirnantian glaciation.

14. • Perhaps there were short periods of
decreased pCO2 that coincided with the
cooling and extinctions. This evidence does
not yet exist but is a topic of considerable
interest among Earth scientists.

16. • The Mesozoic Era begins at the end of the Permian
Period. Mass extinction had eliminated most of the species
of life that had existed throughout the Paleozoic Era.
• Dating from 245-65mya, the Mesozoic (Middle Animals)
Era, the age of the dinosaurs, mark the beginning of land
animals and plants. During this Era, Gymnosperms (seed
bearing lant) first evolved, invading deep into new territory
away from shores where water was plentiful. As these new
plants moved inland, animals soon followed. The dinosaurs
evolved, flourished in every habitat on land, then re-
invaded the oceans.
• The Mesozoic ended as the dominant dinosaurs died after
a meteor struck the Earth, changing the environment. The
first mammals and birds appeared during the Mesozoic
Era, surviving in specialized niches as the dinosaur
continued its control on most of the available niches.
Mesozoic Era.

18. • Geology:
• At the beginning of the Triassic Period, all of the continents were
lumped together into a large continent called Pangaea. There was
no Atlantic ocean at this time. Approximately 135 million years ago,
this continent broke up into two major landmasses: Laurasia and
Gondwana. 35 million years later, Gondwana broke up into
present-day South America and Africa. The Indian subcontinent
began its 8000-km journey pursuing Asia. 45 million years ago,
Australia, like South America, became independent of Antarctica.
• The Continents
• At end of the Paleozoic Era the land that would become the continents
of Europe and Asia crashed into North America. By the time of the
Mesozoic Era Pangea the super continent had formed.
• Climate During The Mesozoic Era
• Climate in the Mesozoic was generally warm and wet.
The temperatures, both on land and in the ocean, were much higher
than during the Paleozoic, and climates were more tropical in nature.
Despite this, the seas were lower, leaving different types of land masses
for life to deal with. Over all the Mesozoic Era was dryer than in the
Paleozoic Era. There were more deserts and less marshland.

19. • Animal Life:
• Almost anyone who thinks about the Mesozoic will think "
dinosaur" at the same time. After all, the Mesozoic has
been dubbed "The Age of the Reptiles." Different types
of reptiles existed:
• The Anapsids are the turtles and tortoises. They were
much more numerous then than now.
• Euryapsids included the pterosaurs and the reptiles of
the sea.
• Synapsids, mammal-like reptiles, later declined
drastically, but they evolved into mammals.
• Diapsids include all of the dinosaurs, and other reptiles in
the Mesozoic.
• Dinosaurs were not the only ones, though. Insects had
large developments, the first inconspicuous mammals
appeared, and swimming and flying reptiles conquered
the sea and sky.

21. • During the Mesozoic
Era, when the
dinosaurs lived,
conifers dominated
the landscape. These
slow-growing
evergreen trees and
shrubs probably
constituted the
majority of the
herbivorous dinosaurs'
diets. Conifers were
probably important
food for dinosaurs,
including the large
sauropods.

22. • Glossopteris, a
tree-like seed fern
(Pteriosperm) from
the Permian
through the
Triassic Period. It
had tongue-shaped
leaves and was
about 12 ft (3.7 m)
tall. Glossopteris
was a dominant
plant in Gondwana
(the southern
supercontinent)
early in the Triassic
period.
Williamsonia
sewardiana was a
cycadeoid (a
bennettitalean). It
had a woody stem
and simple leaves.

23. • The animals that developed in the Mesozoic Era needed new body
types to survive the extremes of temperature and moisture.
Amphibians developed respiratory mechanisms that allowed them to
live in or out of the water for extended periods of time. But it was the
reptiles that were better adapted to the warmer dryer conditions. They
developed thick, leathery skin on both their own bodies and their eggs.
The reptiles thrived, dominating the landscape in both size and
numbers. They are known as diapsids. Diapsids are characterized by
having two openings on each side of the skull behind the eyes.
• The dinosaurs evolved from these reptiles and were themselves
diapsids. During the Jurassic and Cretaceous Periods the dinosaurs
ruled the earth.
• Mass Extinction Ends The Mesozoic Era
• Another mass extinction occurred at the end of the Cretaceous Period,
bringing an end to the dinosaurs and many other species. While this
event did not match the Permian Extinction in the destruction of life it
was the second most devastating in the fossil record. It is commonly
believed that an impact of an asteroid was the cause of this event.