Grade 1 - A History Of The Earth

The History of the Earth: Supplemental Guide 8A | Dinosaurs 151

Presenting the Read-Aloud 15 minutes

Dinosaurs

Hey there, fellow scientists! It’s Pam the Paleontologist again.

Last time I was here, I gave you a whirlwind tour of the history

of life on earth right up through the time of the dimetrodons, the

fi rst giant reptiles that had big sails on their backs. The age of the

dimetrodons was followed by a time known as the Age of Reptiles.

This era, according to some scientists, began approximately 245

million years ago.^1

 Show image 8A-1: Tyrannosaurus Rex skeleton

This is a Tyrannosaurus Rex, or T. Rex as some people call

it. It was one of the largest and most fearsome predators ever

to walk the earth. 2 We can tell by its teeth that the T. Rex was a

meat eater. We also know that it was over forty feet long and up to

twenty feet tall. Judging by the size of its bones, it weighed about

seven tons, or more than two average-sized cars.

 Show image 8A-2: T. Rex and Triceratops^3

This painting shows T. Rex facing off against a triceratops, a

dinosaur with long horns and a shield-like plate on its head. 4 Keep

in mind when you look at artwork like this, that nobody today really

knows what dinosaurs looked like. We have only seen their bones.

Artists use information supplied by scientists today to try to make

good guesses about what dinosaurs looked like when they were

alive. They do all this based on their bones! Many people think of

dinosaurs as giant reptiles, and in fact, the word dinosaur means

“terrifying lizard.” However, many paleontologists now believe

that dinosaurs are more closely related to birds than they are to

lizards. Whatever the case may be, there are no dinosaurs on earth

anymore. They have all been extinct—dead and gone—for many,

many years.^5 Now there are just fossilized bones of dinosaurs

buried in the earth’s crust.

1 This is a very, very long time
ago—long before humans existed.
Dinosaurs and humans never lived
on the earth together.

2 A predator is an animal that eats
other animals.

3 How are these two dinosaurs alike,
and how are they diff erent?

4 Here, the word plate means a fl at,
hard piece that covers the bodies of
some animals. The word plate also
has other meanings. The word plate
can also mean a fl at and usually
round dish that is used for eating or
serving food.

5 If something is extinct, is it still
around today?