Era means "middle
animals", and is the time during which the
world's fauna changed drastically. The era is
divided into three time periods: the Triassic,
the Jurassic , and the Cretaceous .
Triassic, 248 to 206 million years
ago, was a time of transition. Triassic organisms
belonged to one of three groups: survivors of the
extinction, new groups which flourished briefly,
and new groups which went on to dominate the
began to break up about
200 million years ago.
Jurassic, 208-146 million years ago,
dinosaurs dominated the land, the first birds
appeared, and small rat-sized animals became the
first mammals. Ferns, ginkgoes, bennettitaleans
or "cycadeoids" and cycads flourished;
conifers were also present. In the sea,
cephalopods, sharks, rays and giant marine
crocodiles could be found.
The North Atlantic Ocean formed
as North America separated from Africa, Europe
and South America. As North America
pushed westward, the west coast entered a period
of new tectonic activity.
As the continents
separated, portions of the eastern Avalon
Terrane pulled away from North America;
eventually becoming southern Ireland,
Wales, southern England, parts of
Portugal and Spain, northern France,
Holland and Germany.
Similarly, portions of
the coast of Africa were pulled away by
North America. Most of the land east of
the Appalacians and south of Long Island
was previously part of Africa.
ATLANTIC COASTAL PLAIN AND CONTINENTAL SHELF
Cretaceous, 146-65 million years
ago, saw the first appearance of many modern
lifeforms - flowering plants and the co-evolution
with animal pollinators, butterflies, aphids,
grasshoppers, gall wasps, termites and ants.
The breakup of Pangaea
led to increased regional differences in floras
and faunas between continents.
extinctions mark the end of the Cretaceous Period,
65 million years ago. The dinosaurs died out,
along with the marine reptiles such as the
ichthyosaurs, plesiosaurs, and mosasaurs, and the
pterosaurs;. yet other groups of organisms, such
as flowering plants, gastropods and pelecypods
(snails and clams), amphibians, lizards and
snakes, crocodilians, and mammals survived.
The Atlantic Ocean is still growing,
some 180 million years after it began to open.
Animation of the growth of the Atlantic Ocean by Christopher
At the mid-ocean ridge, new crust is formed via volcanic
activity. The new crust then moves away from the ridge.
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