How It Works-Book Of Dinosaurs

It’s somewhat frightening to

imagine what it must have been like

to wander around the plains of

A frica and A rgentina 100 million years ago.

Whereas today you’d be hard-pressed to

encounter a beast any bigger than yourself,

back then you’d be running for your life as

bus-sized creatures roamed free, some

remaining largely peaceful and distant,

others full of aggression.

The biggest land-based animal alive today

is the A frican bush elephant, w ith the largest

weighing a measly 13.5 tons and measuring

10.6m (34.8ft) long and 4.2m (13.8ft) high.

A rgentinosaurus, the current offi cial

record-holder for largest dinosaur of them all,

would have been at least four times the size. It

was a sauropod, dinosaurs of the Jurassic and

Cretaceous period that were mostly

herbivores and know n for being ver y large.

Indeed, many other t y pes of sauropod would

have stood tall above the A frican bush

elephant, as would raptors and pterosaurs.

Dinosaurs inhabited the Earth for much

longer than any modern animal, from 251 to

65 million years ago, allowing plenty of time

for certain species to develop into the giant

hulks of fl esh we now so revere. The biggest

dinosaurs discovered to date have largely

been determined to live in the Late

Cretaceous period, 99.6-65.5 million years

ago, before they faced extinction.

For a long time, though, palaeontologists

have wondered why dinosaurs grew to be so

large. While impressive, size can also be a

hindrance. Not only does a large animal need

a much higher rate of metabolism, but it must

also develop much stronger bones and

skeletal structures to be able to hold itself

upright. Many of these gigantic animals were

also cumbersome and slow, leaving

themselves open to attack from large

predators. Why did dinosaurs continue to

grow for millions of years, then?

One train of thought is that there was a

huge surplus of carbon dioxide in the

atmosphere during the age of the dinosaurs.

This meant that vegetation fl ourished, and

herbivores such as the sauropods simply had

an over-abundance of nourishment available

to eat. While somewhat of a burden in terms

of manoeuvrability, their size would

certainly have helped to some extent when

fending off smaller carnivores. This leads to

another proposal from palaeontologists,

namely that some dinosaurs grew in size over

millions of years as a form of self-defence.

However, others think that these giant

dinosaurs were cold-blooded, which was

directly responsible for their size. Indeed,

warm-blooded animals simply wouldn’t be

able to sustain such mammoth sizes,

somewhat backed up by the lack of mammals

larger than a few tons today.

Huge cold-blooded sauropods, weighing in

at up to 100 tons, would have been almost

self-sustainable, as they could store heat

throughout the day for the colder nights,

maintaining a fairly unchanged body

temperature and prolonging their sur v ival.

How were they

supported?

We examine the anatomy of a

sauropod, to see how these huge

creatures were able to keep upright

Bridge

The structure of a sauropod such as

the mammoth A rgentinosaurus was

very similar to that of a modern-day

suspension bridge

Neck

Muscles in the neck of a sauropod

were connected to ribs by elastic

ligaments, allowing movement but

also providing ample support

Vertebrae

A huge tendon ran all the

way from the neck to the

tail inside a groove on the

spines of the vertebrae

© Science Photo Librar y © Science Photo Librar y

DID YOU KNOW? (^) The biggest animal ever known to have lived on Earth, including dinosaurs, is the blue whale
The hollow bones of a pterosaur
ensured it remained light enough to
achieve fl ight, even when reaching
the size of a small plane
Pterosaur