Listen to part of a lecture in a zoology class.
Your reading for today touched on dinosaur fossils from the Mesozoic era, which ended about 65 million years ago.
Today we will be discussing the sauropods.
I think our discussion of sauropods will illustrate what we can learn by comparing the fossil record to modern animals.
By fossils, we mean traces of prehistoric animals such as bones, which become mineralized, or impressions of bones or organs that are left in stone.
Now sauropods were among the largest animals to exist ever!
They were larger than blue whales, which are the largest animals alive today.
They weigh up to one hundred tons, twenty times as much as elephants.
Also, they were an extremely successful kind of dinosaur.
There's evidence of sauropods in the fossil record for an unusually long time, over one hundred million years.
So, why were sauropods so successful?
Biologically speaking, sauropods shouldn't have been successful.
Large animals like elephants, say, they require much more food and energy and have fewer offspring than smaller animals.
This makes maintaining a population harder.
The largest animals today don't live on land, but in the ocean where food is easier to find.
A blue whale, for instance, can eat up to 8,000 pounds of food a day.
And they give birth only once every few years.
We also know that body heat, that… well, large animals can't easily get rid of excess body heat.
But for an oceangoing whale, that's not a problem.
For a 100-ton land animal, it can be.
For years, we have assumed it was the abundant plant life of the Mesozoic that allowed these giants to thrive.
However, we now know that since oxygen levels were much lower in the Mesozoic than we assumed, there was much less plant life for sauropods to eat than we thought.