Cambrian
510 Ma
PALEOZOIC ERA
|
Development of algae. First vascular plants. Evolution of
invertebrates. The "Cambrian Explosion" of invertebrate
diversity. Trilobites, early arthropods which are now extinct, appeared.
Trilobites were the first animals to "see" the world around
them. Evolution of echinoderms. |
A single large continent at the south pole, Rodinia, broke apart into
Laurentia, Baltica, and Siberia. Laurentia, which is destined to become
N. America sits on the equator. Baltica is below it and Siberia is to
the right. |
 |
Ordovician
470 Ma
PALEOZOIC ERA
|
Evolution of jawless fishes, coelenterates, arthropods, cephalopods. |
. |
 |
Silurian
430 Ma
PALEOZOIC ERA
|
Numerous coral reefs, first widespead land plants, first dry land
animals (arthropods), first jawed fishes. |
Laurussia (old red continent) forms from Laurentia and Baltica |
 |
Devonian
400 Ma
PALEOZOIC ERA
|
First forests and insects. Origin of amphibians. |
Lauasia, off to right, has formed from other blocks which broke off
from Rodina. |
 |
Carboniferous
(Mississippian)
340 Ma
PALEOZOIC ERA
|
Between the Devonian and Permian, the first club mosses, horsetails,
and ferns appeared. First winged insects, reptiles and gymnosperms. |
Remains of Rodina at the south pole, called Gondwana, move north to
collide with North America (Laurussia) to form Pangea (all land). |
 |
Carboniferous
(Pennsylvanian)
300 Ma
PALEOZOIC ERA
|
. |
Laurasia connects to Pangea through a land bridge in the north. |
 |
Permian
270 Ma
PALEOZOIC ERA
|
By the Permian, only a single trilobite family was left and extinction
was almost at hand. The end of the Permian, about 250 million years ago,
marks the biggest extinction of all time. About 50% of all families and
more than 90% of all species died out. Climates became cooler at the end
of the Permian and lowered temperatures in tropical regions may have
reduced oxygen content in the oceans. There were enormous volcanic
eruptions in Siberia which might have increased carbon dioxide
concentrations in the atmosphere. But, nobody has really good evidence
as to what happened. |
Blocks break off from the left main mass of Pangea (Gondwana) and
cross the Tethys Ocean to collide with Asia. These are what is now
Turkey, Iran, Tibet. |
 |
Triassic
230 Ma
MESOZOIC ERA
|
The mesozoic plants were dominated by ferns, cycads, ginkgophyes, and
other strange plants. The early Triassic saw evolution of gymnosperms
and modern corals. Ammonites, a group of now extinct cephalopods with a
many chambered spiral shell, evolved into an increasing number of forms.
Explosion of reptilian diversity. First frogs and dinosaurs. First
mammals evolve from mammal-like reptiles. |
|
 |
Jurassic
170 Ma
MESOZOIC ERA
|
Dominance of the dinosaurs. First birds appear. |
Pangea begins to rotate. Because different parts rotate at slightly
different rates, the continent tears apart. The Gult of Mexico and
Atlantic Ocean form on the left side of the Tethys Ocean. |
 |
Early Cretaceous
120 Ma
MESOZOIC ERA
|
Evolution of birds and origin of the three modern mammal groups:
monotremes (echidnas and platypus), marsupials, and placentals.
Co-evolution of flowering plants and animal polinators. Flowering plants
are so successful that they begin to dominate the vegetation. |
North and South America begin to separate. Europe separates from North
America. Off to the right, at the bottom of what is going to become
Africa, India and Australia are breaking off. |
 |
Late Cretaceous
70 Ma
MESOZOIC ERA
|
Extinction of the ammonites. First, sea reptiles become extinct, then
dinosaurs. The extinction is termed the KT event from K or Kreta (chalk)
and T for Tertiary, another name for the following geological period.
During the KT event, 20% of the families of plants and animals on land
and 50% in the sea became extinct. The extinction event may have killed
some groups over a period as short as thousands of year. But the
dinosaurs probably took millions of years before they became extinct. |
Africa breaks off from South America. Florida and Kansas are under the
ocean! |
 |
Ecocene
40 Ma
CENOZOIC ERA
|
After extinction of the dinosaurs, mammals radiate into ecological
nitches formerly occupied by dinosaurs. Placental mammals evolve. First
primates appear in the late Cretaceous as one of the first groups of
placental mammals. Monkeys appear in the Ecocene and the first true apes
appear more than 25 million years ago. |
India is moving north towards Asia and Australia is moving east. |
 |
Miocene
20 Ma
CENOZOIC ERA
|
Gorillas appeared at about 9 million years ago and the human and chimp
lineages separated about 5-7 million years ago. |
India has crashed into Asia, forming the Himalayan mountains. The
Rocky mountains grow and the Alps form. |
 |
Present
|
|
Evidence indicates that a new continent may form in the future around
the North Pole. |
 |
