How It Works-Book Of Dinosaurs

The mass extinction at the end of the Cretaceous period

followed four others. The fi rst signalled the end of the

Ordovician period, which existed between 490-440 million

years ago. The area to the north of the tropics was almost

all ocean and the nature of the thriving marine faunas

changed and the land saw the arrival of arthropods, such

as Eodalmanitina, Cyclopyge and the Triarthrus. This mass

extinction hit the fl ora and fauna, eroding much of the

ecosystem of the most primitive creatures.

Next came the mass extinction at the end of the

Devonian period (420-360 million years ago). This

effectively wiped out around three-quarters of the Earth’s

species, though this could have taken the form of several

extinctions over many millions of years rather than

occurring as a result of a single event. The mass extinction

at the end of the Permian period (300-250 million years

go) wiped out 96 per cent of the Earth’s species, meaning

all that exists today is descended from the four per cent

that remained. The penultimate mass extinction occurred

at the Triassic-Jurassic period (250-140 million years ago),

with climate change, fl ood basalts (that come as a

result of a volcanic eruption coating the Earth

with basalt lava) and asteroid impact all

being possible causes.

Events of mass extinction

The end of the

dinosaurs is

commonly disputed

among scientists

DID YOU KNOW? (^) The Cretaceous-Tertiary mass extinction is also commonly referred to as the K-T extinction
“The common factors in mass
extinctions include large-scale
lava flow and volcanic gases”
Volcanic
eruptions
Common factors in
extinction events is
the presence of lava
and volcanic ash
Fauna
The Corythosaurus is
theorised as being the
last dinosaur standing
after the mass-
extinction event
Plant survival
After a mass extinction event,
it is common for there to be
recovery. After the dinosaurs
became extinct, the plants,
mostly ferns, .became the
dominant survivor