How It Works-Book Of Dinosaurs

What’s inside a

dinosaur egg?

Just like modern day baby chicks, dinosaurs

grew and hatched from eggs to roam the

planet a very long time ago

What came fi rst – the dinosaur or the

egg? We’re not entirely sure, but what

we do know is that these great reptiles

laid eggs just like chickens do. Inside the shell

of a hen’s egg, chicks are able to grow before

they’re ready to hatch. That’s just how the

dinosaurs were born.

We know that baby dinosaurs were made this

way because we have found lots of ev idence.

Fossilised dinosaur eggs have been found at

over 200 places across the world. They tell a

stor y about how the dinosaur made its nest, laid

its eggs and how baby dinosaurs were born.

A crew of palaeontologists exploring

Mongolia in 1923 were the fi rst to scientifi cally

recognise fossilised dinosaur eggs for what they

were. Since then many dinosaur nesting sites

for many different species have been uncovered

all around the world. The oldest known

dinosaur eggs and embryos date back to the

Early Jurassic (about 190 million years ago) and

come from the Massospondylus, a bipedal,

omnivorous prosauropod.

Egg Mountain in Montana, USA is the site of

one of the most famous dinosaur nest

discoveries. Maiasaura remains were found

near a nest with the remains of eggshells and

babies too large to be hatchlings and this is the

reason why Maiasaura is known as “caring

mother lizard”. Maiasaura and many other

species of dinosaur, raised their young in nest

colonies. This relfected the way that they

herded when on the move. This amazing

discover y was the fi rst proof that dinosaurs

raised and fed their young, rather than leaving

hatchlings to fend for themselves like modern

turtles do. Nests contained approximately 30-40

eggs and were not incubated by the parent

sitting on them, but by the heat produced from

rotting vegetation placed in the nest. It’s

thought that Maiasaura hatchlings left the nest

after a year or two of rapid grow th.

DINOSAURS

Inside an egg

A very thick liquid protected

the young dinosaur inside.

Without this, he or she would

not have been able to survive

A thick liquid

The egg might be hard, but the

baby was able to breathe air

through little holes. These were

so small that they would have

been very hard to see

Breathing easy

The baby dinosaur grew very fast, a

lot faster than any bird or animal we

know of. This happened both inside

the egg and out

Growing up fast

How a dinosaur is made inside an

egg is very similar to the birth of

many of today’s birds and reptiles

Just like

chickens and

crocodiles