Most dinosaurs had flat teeth and ate only plants. There were many kinds of leaves, fruits, roots, and cones to feed on. Long-necked plant-eaters may have browsed from high trees to feed its bulk. Shorter dinosaurs may have pulled plants from the undergrowth. Some dinosaurs had sharp teeth and ate meat. The ferocious meat-eaters hunted other dinosaurs. Smaller ones ate lizards, frogs, or even fish.

      Some dinosaurs walked on two legs. Some walked on four. Others could do both. There were dinosaurs that moved fast. Some were slow and lumbering.

      Then, the dinosaurs disappeared. Whatever happened to them 65 millions years ago is still a mystery. Now only bones, teeth, claws, footprints, and sometimes prints of dinosaur skins are left to tell their story.

      I am Paulino. I became interested in dinosaurs when I was three years old. I am now six years old-going seven in three months.

      My big brother tells me that I am a dinosaur expert. Why, I have been studying dinosaurs as long as he has been studying high school! I have read all my books-all fifty of them-about dinosaurs. I have watched dinosaur feature stories on the National Geographic and Discovery television channels-even cartoons and movies about dinosaurs. Yes, I can say that I know as much about dinosaurs as the scientists who study them.

      So, why did the dinosaurs die out? There are many kinds of theories about this. A theory is an explanation that might be possible. Some of the dinosaur theories are ridiculous. Some are more likely.

      Some people said that a contagious disease attacked the dinosaurs. They all got really, really sick. Then they all died out. Gone forever?

      Perhaps smaller animals ate the dinosaur eggs until no more eggs were able to hatch. But where were the mother dinosaurs! My mother would not let this to happen to her babies.

      Some scientists said that there were huge volcanic eruptions. These explosions created a big blanket of dust, blocking out the sun. Without much sunlight, enough plants died. The plant-eaters ran out of food. Then the meat-eaters died, too. There were no more for them to gobble up!

      Some scientists believed that a large comet smashed into the earth. It caused fires that killed lots of dinosaurs. The collision also sent huge amount of dust and ash into the air, blotting out much of the sun’s rays. The temperature around the earth dropped below freezing. So used to the warm, moist climate, the surviving dinosaurs could not cope with the cooler Earth.

      There are also scientists who suggested that the dinosaurs probably live on today as birds. It was all in the hips, they said. There were two groups of dinosaurs. One group was lizard-hipped. The other was bird-hipped. But what made these scientists think that dinosaurs came from birds is the fossil imprint of an ancient winged animal. It shows faint outlines of teeth and bones like those of dinosaurs.

      That dinosaurs turned into birds is still an idea hotly argued about by scientists. So are the other theories. With only fossils as clues to the mysterious disappearance of dinosaurs, scientists will keep trying to find out which theory is the right one.

      Now, I, Paulino the dinosaur expert, have an explanation of what became of dinosaurs.

      After the great volcanic eruptions, many dinosaurs died. Many more died after the giant comet hit the earth. But the tough dinosaurs did not die. They were just too tough to die. They had to stay alive!

      Size was an advantage, the surviving dinosaurs soon found out. The smaller dinosaurs had it easy finding food because they were nimbler and more agile. And they could fill up on just a few plants. But the bigger dinosaurs had to eat tons and tons of food everyday just to stay alive. It was really hard work finding so many food. So over the years, the bigger dinosaurs got smaller and smaller and smaller.

      During the time of great change, the climate got colder and colder. The earth thickened with snow. Glaciers and ice sheets extended over large areas. The dinosaurs had to keep themselves warm so they grew hair on their skin.

      The surface of the earth then began to take shape. Lakes were being formed. Paths of rivers were changing. New mountains were appearing. Land was eroding. The first grasses appeared. The dinosaurs realized that moving around on two legs was easier and more practical. So they began to straighten their backbones until they were able to stand tall and walk on two legs. At first, the four-legged ones had difficulty changing their gait. But they soon were able to get the hang of it.

      About this time, the dinosaurs did not look like dinosaurs anymore. They had dropped off their plates, crests, spikes, clubs, or frills. They did not need them anyway. They had already made useful tools such as stone knives, hammerstone, and scrapers. By striking stones upon one another, they made one important discovery-fire!

      Becoming sophisticated and sociable, the dinosaurs had developed elementary speech. At night, they huddled around the fire they had built to keep them warm. They told each other stories, and perhaps laughed at each other’s jokes.

      “Really now, Paulino!” said my big brother, after putting down the picture storybook I had made. “We came from dinosaurs!”

      “And why not?” I challenged him. “Dinosaurs were intelligent. They lived for millions and millions of years! No stupid creature could live that long! So dinosaurs would know how to evolve into other forms. They would know how adjust to the changing surroundings.”