Martin Carroll, age 7, of Burlington, Vt., for his question:

HOW LARGE WAS THE LARGEST DINOSAUR?

Dinosaur is the common name for two groups of reptiles that lived on earth millions of years ago. The saurischia (pronounced saw rihs kee uh) had hips similar to those of modern lizards while the ornithischia (pronounced awr nih this kee un) had birdlike hips.

A member of the lizard hipped dinosaur group, a gigantic plant eater called a Brachiosaurus, was the largest of all the dinosaurs, even though it had a rather short tail. This monster was 70 feet long and weighed 85 tons. Longer but not weighing as much was the 80 foot Brontosaurus and the 90 foot Diplodocus.

Scientists say the large dinosaurs lived to be more than 100 years old.

The largest meat eating dinosaur, the Tyrannosaurus, measured about 45 feet from his head to his tail. He stood 20 feet high and had a four foot head with six inch daggerlike teeth.

A typical member of the bird hipped dinosaur group was about 18 feet long.

Not all dinosaurs were giants. One variety grew to be only two and a half feet long.