Ann Nadig, Age 11, of Allentown, Pa., for her question:

Why did the dinosaurs die out?

They ruled the world for 180 million years. Many of them were giants bigger than the biggest elephants. Some of these giants were armed with spears and spikes and covered with massive plates of protective armor. No one would have suspected that all these mighty animals would perish from the earth. But they did.

The long reign of the dinosaurs came to a rather sudden end. They had lived and thrived in Countless numbers through the Triassic, the Jarassic and the cretaceous periods of earth's history. Then suddenly they were gone. There were no dinosaurs to greet the Tertiary Period, which opened some 60 million years ago.

We cannot say for certain why the Age of reptiles ended when it did. But most likely a number of changes worked together to put an end to the mighty lizards. The world climate, which had pampered the dinosaurs for 180 million years, took a turn for the worse. For ages, the whole earth had basked in heat and humid moisture. This climate now retreated to the tropics, leaving two frigid polar regions and the Cool temperate zones.

The Seas withdrew from many marshy coast lines, and the cooler weather was crisp and dry. These conditions did not suit the scaly skinned lizards, and most of them had become too set in their ways to change. The bulky creatures could not adjust themselves to cope with the new world. Many of them perished from cold and drying air. Many starved when their favorite marsh weeds were left high and dry by the retreating seas.

Some experts suggest that the end of the dinosaurs may have been hastened by the mammals. These furry, warm blooded fellows were but new arrivals in the world. They were suited to a cooler climate.

They were not very smart, but they were a lot smarter than the dinosaurs. The little mammals most likely found dinosaur eggs and fed upon them. This would reduce the dinosaur population. But a world wide disaster, such as a drastic change of climate, was needed to destroy them all.

The dinosaurs left their giant bones along with other fossils in the earth. Plant fossils tell a story of the changing climate which may have sealed the doom of the big reptiles. Tropical plants retreated from the polar regions to the middle latitudes and finally backed up to warm belts north and south of the equator. The bulky dinosaurs were highly specialized animals, and they could not adapt themse1ves to such drastic changes in their world.