Quartenary Period
The most recent period in Earth’s history: Pre-humans
appeared at the beginning of this period, which also saw
the rise (and fall) of giant mammals such as woolly
mammoths. The last glacial ice sheets retreated during
the last 20,000 years of this period.
Paleogene-Neogene Periods
The earliest grasses appeared at the beginning of the
Paleogene, which followed the mass extinction of
dinosaurs. These grasses allowed mammals to flourish
during the Neogene, when grazing animals and the
carnivores that hunted them were bountiful.
Cretaceous Period
This long period of 75 million years saw the earliest
flowering plants. The dinosaurs ruled the land and skies
during this time, but would die suddenly with an asteroid
strike 65.5 million years ago, ending the period.
Jurassic Period
Everyone knows of Jurassic Park: The Jurassic Period
was a time of abundant dinosaurs and ammonoids, a
shelled sea creature. The first birds, relatives of
dinosaurs, appeared toward the end of the Jurassic.
Triassic Period
The Triassic began following the Permian extinction,
which wiped out 90% of life on Earth. The Triassic saw
the rise of the dinosaurs and the first mammals.
Permian Period
The Permian was an age of abundant reptiles and
mammal-like reptiles. The trilobites, which had lived on
Earth for 250 million years, would go extinct at the end
of the Permian.
Carboniferous Period
This period following the Devonian was a lush age of
dense forests (which today form coal). The earliest
reptiles appeared during the Carboniferous, and
amphibians were abundant during this time.
Devonian Period
Though the Devonian saw the extinctions of many
marine organisms, the period saw many firsts: this was a
time of Earth’s first sharks, first amphibians, and the first
forests—which would seed the Carboniferous period.
Silurian Period
The Silurian was a time of warm shallow seas. Silurian
fossils show extensive coral reefs and the first fish with
jaws. Followed by the Devonian, the Silurian saw the
first land plants and animals, including flying insects.
Ordivician Period
During the Ordivician, which came before the Silurian,
life still lived in the sea. The period is best known for its
diverse marine invertebrates, including trilobites. The
first corals and primitive fish appeared during this time,
Cambrian Period
The Cambrian marked the explosion of complex life in
the oceans 542 million years ago. Major groups of
animals appear in the fossil record, including the
trilobites. It was followed by the Ordivician.