Mesozoic Era is comprised of three periods:
- Oxygen levels started out low at the beginning of the Era as
a consequence of the Permian Extinction; however, they plummeted
even lower at the end of the Triassic, instigating another mass
- The low oxygen of the Triassic was the lowest ever
experienced by Life on Earth.
- Throughout the Jurassic and Cretaceous the levels
continued to climb, reaching near-modern levels.
- Carbon dioxide levels,
high at the beginning of the
Triassic, fell quickly, reaching near-modern levels as well.
- From the late Triassic onwards, carbon dioxide continued
to rise, until the Cretaceous when it began a gradual
- Pangea, the vast single continent formed in the late
Paleozoic, had begun to break apart early in the
- By the end of the era, many island continents had
formed, including North America, Africa and India.
- The basin of the Atlantic Ocean continued to spread as
the continents drifted apart.
- Sea levels were at their lowest levels ever, but by the
Cretaceous the sea levels had risen to the extent that many of
the continents were covered by shallow seas.
- The arid landscape of the Triassic was eventually replaced
by the warm, moist environs of the Jurassic.
- The Cretaceous saw a cooling trend as the glaciers grew once
again at the poles having been absent during the Jurassic.
Nevertheless the Cretaceous remained warmer than today due to
elevated carbon dioxide levels.
- Fossils of dinosaurs can be found at the extreme north
indicating a mild climate.
sparsity of vegetation in the Early Triassic led to a
distinctive lack of
coal deposits in the early Mesozoic.
- As carbon dioxide levels climbed, the plants rebounded.
- Some of the Paleozoic species survived and continued on in the
Mesozoic, adapting to the changing conditions and reinventing
- The angiosperms (flowering plants) arrived during this era
and revolutionized everything from the landscape, to the
available habitats for insects, mammals and reptiles, and most
importantly, their diet.
- By the end of the era, they constituted about 90% of all
- Dinosaurs first appeared in the late Triassic and would come
to dominate the remaining periods.
first appeared in the late Triassic, though they remained small
throughout the Mesozoic.
- Some of the significant developments in the mammalian
realm was the appearance of three new reproductive methods.
Even today, the mammalian world is divided into three groups
based on these reproductive methods that emerged in the
- Placental mammals
Pterosaurs formed another significant branch of life,
appearing in the late Triassic along with their dinosaur
- Forming into a variety of species, the continued to grow
in size until some species reached gigantic proportions by
- Along with the pterosaurs, were the early birds, their
best-known representative being Archeopteryx.
- The oceans teemed with life as huge creatures darted through
its waters, including mosasaurs, icthyosaurs, giant turtles and
- Coral reefs flourished in the warm waters, covering
enormous stretches of ocean shallows.
- Insects continued to diversify, adapting to new plants and
- With the appearance of the angiosperms, the insect way
of life was revolutionized by the need for
- Grasshoppers, flies, ants, bees and wasps are just a few
of the new types of insects to appear during this era.
- The three main extinction events occurred during the Mesozoic era:
the asteroid impact bringing the Era to a close and issuing in a
new way of life.
- Cretaceous (asteroid impact)