How It Works-Book Of Dinosaurs

95

Dinosaurs weren’t

the fi rst reptiles to

rule the Earth

Around 300 million years ago amphibians

dominated Earth, but as it got warmer,

reptiles took over. There were pelycosaurs,

mammal-like reptiles called therapsids, and

archosaurs, from which dinosaurs,

crocodiles and pterosaurs evolved.

96

Dinosaurs

lived for up

to 300 years

Paleontologists estimate the large

dinosaurs had life spans ranging from

75 to 300 years. These estimates were

made based on information we have on

cold-blooded animals – warm-blooded

creatures have shorter lives.

97

Troodons were

probably the

cleverest dinosaurs

Troodons lived around 77 million years

ago and were about two metres (6.6

feet) long. They were carnivores,

walked on two legs and had relatively

large brains. They are also thought to

be related to modern birds.

98

Amber insects

don’t contain

dinosaur DNA

Jurassic Park is based on the idea that you

could extract dinosaur DNA from blood

preserved inside the bodies of mosquitoes

encased in amber. Despite several

attempts to recover DNA, it seems it

doesn’t actually survive inside the amber.

Hunting dinosaurs

83

Chicxulub crater marks

the asteroid impact that

killed the dinosaurs

Chicxulub crater in Mexico is a 66 million-year-old,

180km (112mi)-wide impact created by a 10km

(6mi)-wide asteroid. It is thought to represent the

aftermath of the impact that killed the dinosaurs. In

2016, scientists plan to drill into the crater to learn

more about its history.

79

North America has

excavated the most

dinosaur fossils

North America, Argentina and China have

more than their fair share of dinosaur

fossils. Areas with desert-type

environments prevented the build-up of

thick layers of plants, leaving the remains

easier to fi nd under sand and rock.

81

Fossilised dinosaur

highways allow us to

retrace ancient steps

Enormous mudfl ats captured the imprints of

dinosaur footprints, and some were preserved

as fossils. Utah in the United States is

particularly famous for its dinosaur

trackways, which can be found on what used

to be an ancient muddy fl oodplain.

82

New dinosaurs

are discovered

every year

There are hundreds of dinosaur

fossils still to be discovered, and a

new dinosaur is found and named

approximately every seven weeks.

84

Dinosaur bones can

be recognised by

distinctive skull holes

All dinosaurs have the same basic skull, with

two holes for jaw muscles behind the eye and

an air socket between the eyes and nose.

85

Dinosaur bones can be

aged by radiometric dating

Carbon dating doesn’t work on dinosaur bones, so

scientists estimate the age of fossils by measuring

radioactive isotopes in the surrounding rocks.

JURASSIC

COAST

South coast, UK

CANDELEROS

FORMATION

Argentina

CLEVELAND-LLOYD

DINOSAUR QUARRY

Utah, USA

Giganotosaurus

Late Cretaceous

South America

Ankylosaurus

Late Cretaceous

North America

DINOSAURS’ LEGACY

101 dinosaur facts

Fossils have be found on

every continent on Earth...

80

The fi rst dinosaur fossil

was found in England

The fi rst dinosaur to be scientifi cally documented was

Megalosaurus, formally named by William Buckland in

1824. The fossils were found in a quarry in Oxford.