The document discusses theories about the extinction of dinosaurs. It notes that dinosaurs ruled the Earth for around 150 million years, spanning the Late Triassic, Jurassic, and Cretaceous periods. However, one of the largest mass extinctions occurred around 65 million years ago at the end of the Cretaceous period, wiping out dinosaurs and many other species. Several theories for this extinction have been proposed, including toxic gases from volcanic eruptions, an asteroid impact, food shortages, or climate change, with some scientists believing a combination of factors was responsible.

1. DINOSAUR EXTINTION

2. DINOSAUR EXTINCTION THEORIES
T H E F I R S T D I N O S A U R B O N E S W E R E P R O B A B L Y D I S C O V E R E D
B Y C H I N E S E S C H O L A R S I N A N T I Q U I T Y. H O W E V E R , I N E U R O P E
T H E F I R S T R E C O R D E D D I S C O V E R Y W A S N ’ T U N T I L 1 6 7 7 . B Y
1 8 4 2 I T W A S R E A L I S E D T H A T P R E H I S T O R I C R E P T I L E S H A D
O N C E I N H A B I T E D T H E E A R T H . T H E N A M E D I N O S A U R I A W A S
P R O P O S E D T O D E S C R I B E T H I S G R O U P .
R E P T I L E S F I R S T A P P E A R E D A B O U T 3 2 0 M I L L I O N Y E A R S A G O
( M A ) , T O W A R D S T H E E N D O F T H E P A L A E O Z O I C E R A . T H E Y
F L O U R I S H E D D U R I N G T H E M E S O Z O I C E R A W H I C H I S A L S O
R E F E R R E D T O A S T H E A G E O F R E P T I L E S . T H I S E R A I S
F U R T H E R S U B D I V I D E D I N T O T H E F O L L O W I N G P E R I O D S :

4. Triassic
(approx. 250 – 200Ma)
Jurassic
(approx. 200 – 145Ma)
Cretaceous
(approx. 145 – 65Ma)

6. Dinosaurs ruled the Earth for almost
150 million years. This spanned the
Late Triassic, Jurassic and
Cretaceous periods. One of the
largest mass extinctions in Earth’s
history occurred at the end of the
Cretaceous period. It is referred to
as the K-T (Cretaceous-Tertiary)
extinction.

8. Many species, including dinosaurs, pterosaurs, and
large marine reptiles, disappeared virtually overnight.
Today the only living descendents of the dinosaurs are
the birds.
Many theories have been suggested for the extinction
of the dinosaurs. Some of these have dealt with:
toxic volcanic gases and dust
asteroid impact
food shortage
climate change
Some scientists have suggested a combination of
these factors.