The Jurassic Period
million
The Jurassic period was 206-144
ngea
years ago. The supercontinent Pa
o
had began to break apart into tw
and
landmasses, Laurasia in the north
of
Gondwana in the south. The start
the
the Jurassic period is defined by
in
Triassic-Jurassic extinction event
peared
which a third of marine life disap
saurs
and many non-dinosaurian archo
became extinct, other than the
d many
crocodilians, a few therapsids an
the
large amphibians. At least half of
rth
species known to be living on Ea
,
at that time became extinct. Again
scientists aren’t entirely sure what
several
caused this mass extinction, and
d
explanations have been suggeste
or
– climate change, asteroid impact
massive volcanic eruptions.
What was th
e world like
?
As Pangea bro
ke apart into
Laurasia
and Gondwa
na, the ocean
s spread
over the land
and huge are
as were
flooded, leav
ing many sha
llow seas
and creating
milder weath
er. This
creation of m
ore coastline
s meant the
climate shifte
d from dry to
humid and
much of the
arid desert w
as replaced
by rainforests.
Laurasia even
tually
broke up into
North Americ
a and
Eurasia, and G
ondwana beg
an to
break up by th
e mid-Jurassic
period.
What lived on Earth in the Jurassic period?
The Jurassic saw the arrival of sauropods, ‘lizard hipped’ herbivores who walked on four legs,
such as the Diplodocus and Brachiosaurus. They had long necks and heavy tails and some grew
as big as 30 metres and weighed 100 tons – making them the largest animals ever to walk the
Earth! Large carnivorous theropods roamed the land, such as the Allosaurus and Megalosaurus.
All these dinosaurs were saurischian, or lizard hipped, but there were also some ornithischians
such as the stegosaurs and ornithopods, which were medium sized herbivores (not as big as
the sauropods!).
The earliest known bird, the Archaeopteryx, joined the flying reptile pterosaurs which had
been around since the late Triassic and dominated the sky. Some of the earliest small mammals
appeared and conifer trees dominated the plant world!
Allosaurus
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The tallest dinosaur wa
s
the Sauroposeidon and
was
around 18.5 meters tall!
The Stegosaurus had a brain as
big as a walnut! Even though its
body weighed nearly two tons!
Archaeopteryx
Diplodocus
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