During the Jurassic period, the supercontinent Pangaea started to break
up.
So while during the Triassic
all the dinosaus lived on the same continent, now they became isolated
from each other, which created new species, different on every isolated
continent.
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In the early Jurassic Period, the skies
were
inhabited by pterosaurs and the seas were inhabited by Ichthyosaurs
(which now had much more of a dolphin-like shape than during Triassic),
Plesiosaurs,
crocodiles
and turtles.
On the
land, the coelophysid meat-eaters were
the main predators, although a variety of other carnivores started to
evolve as the life began to diversify. Of the lizard-hipped plants
eaters, a few late prosauropods still existed, but the primitive
sauropods
now became prominent. The bird-hipped plant-eaters were still in their
early evolution. The early Ornithopods were small, and armoured
dinosaurs only started to evolve.
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In the mid-Jurassic Period, the
carnivorous Theropods
were widespread and ranged from small animals to large monsters. The
most primitive sauropods - cetiosaurs - had evolved, and along with
them lived the more "modern", bird-hipped dinosaurs such as Ornithopods
and armoured dinasours. Ornithopods were not very abundant, their time
was yet tom come. Armoured dinosaurs - Thyreophorans - heavy,
four-footed animals with plates or spikes on their back and tails -
started to spread. The early forms of stegosaurs, which were abundant
in late Jurassic,
and
ankylosaurs, which would replace stegosaurs in Cretaceous times, were
present.
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In the late Jurassic, the life had
diversified and
different species became more and more established. The oceans could
support a wide variety of marine animals, and the two different groups
of plesiosaurs - plesiosauroids and pliosauroids
- had become quite distinctive. In the skies, there were many different
species of Pterousaurs. The two main types - the more primitive
rhamphorhynchoids still existed while the later pterodactyloids started
to diversify. Some Theropods
(meat-eaters) had become large and scary looking animals, but there
were also many Theropod species that were small. The lizard-hipped
plant-eaters sauropods
had got really large - brachiosaurids and camarasaurids in heigh, and
diplocoids in lenght. The smaller, bird-hipped herbivores such as
ornithopods and stegosaurs
also continued to develop. Jurassic dinosaurs may be the most famous,
but the real advanced dinosaurs were yet to evolve during Cretaceous period.
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