How It Works-Book Of Dinosaurs

© Thin k stock; Science Photo Librar y

Peter Scott / A r t A genecnc y

55

Dinosaurs are still

alive today

In the 19th century the fossilised

remains of a feathered dinosaur called

Archaeopteryx were discovered, and

since then evidence linking dinosaurs to

birds has stacked up. It is thought that

early birds started to evolve from the

carnivorous theropods in the late

Jurassic, and a few managed to survive

the mass extinction, giving rise to the

bird species we see today.

54

There were fewer

dinosaur species

than we thought

Hundreds of species of dinosaur have

been named, but few baby dinosaurs

have been found. Scientists have

reviewed the evidence and have found

that some smaller species might

actually be the babies of larger species.

52

There were more than

700 species of dinosaur

To date, over 700 species of dinosaur have been

identifi ed, but only around 300 have been confi rmed

as entirely unique. There are more yet to be found, so

this number will continue to change.

53

There are hundreds of

dinosaurs yet to be found

It is estimated that we have only found around a tenth of

the dinosaur species that ever existed. Some are buried in

rocks we cannot reach, while others lived in areas where

conditions did not favour fossil formation.

60

Sea levels were at

an all-time high in

the Cretaceous

During the Cretaceous period, sea levels

rose and fell dramatically, and large

areas of land disappeared under water.

At times the sea was 100-250m

(330-820ft) higher than it is today.

61

High oxygen levels

fuelled fi res during the

extinction event

During the Cretaceous period, oxygen levels in

the atmosphere were much higher than they are

now, which may have helped to fuel fi res after

the famous meteor impact 66 million years ago,

contributing to the mass extinction.

62

They experienced

more than one

mass extinction

There was a mass extinction at the

end of the Triassic period, when many

land animals died out, leaving room

for the evolution of some of the giants

of the dinosaur world.

CRETACEOUS 145–66 MILLION YEARS AGO

SPINOSAURUS

RAJASAURUS MAJUNGASAURUS

TROODON

UTAHRAPTOR

VELOCIRAPTOR

THERIZINOSAURUS

MAPUSAURUS

ARGENTINOSAURUS

BRACHIOSAURUS

EUOPLOCEPHALUS

CHARONOSAURUS

DRACOREX

CENTROSAURUS

PROTOCERATOPS TRICERATOPS

PACHYCEPHALOSAURUS

HYPSILOPHODON

IGUANODON

DIPLODOCUS

OVIRAPTOR

SHUVUUIA

CARCHARODONTOSAURUS

GIGANOTOSAURUS

TYRANNOSAURUS

TARBOSAURUS

Brachiosauridae

Neosauropoda

Spinosauridae

Tryannosauroidea

Ornithomimosauria Therizinosauria

Oviraptorosauria

Alvarezsauridae

Dromaeosauridae

Birds

Abelisauroidae

Titanosauria

Pachycephalosauria

Hypsilophodontidae

Ceratopsia

Iguanodontia

Troodontidae

MINMI ANKYLOSAURUS

Diplodocoidea

DID YOU KNOW? (^) A theropod known as Concavenator had a hump on its back like a camel
Ceratosaurus
Late Jurassic
North America,
Europe
Euoplocephalus
Late Cretaceous
North America
Triceratops
Late Cretaceous
North America
Utahraptor
Early Cretaceous
North America