Why Are There No Dinosaurs Today?

       Why Are There No Dinosaurs Today? Why did the dinosaurs die out?

       You may have heard in movies or read in comics some ridiculous reasons for the disappearance of dinosaurs. You might have read that during the Ice Age great sheets of ice moved down and killed them off. Well, it is true that there was an Ice Age. But some scientists believe that it started about a million years ago. And the last of the dinosaurs died out about 75 million years ago. So that means that the dinosaurs had been extinct at least 74 million years before the great ice-sheets started slowly moving down out of the North according to their beliefs.

       Perhaps the cave men killed all the dinosaurs, as a certain movie suggested. No, absolutely no! Just remember that millions and millions of years before the first prehistoric people lived, the last of the dinosaurs had vanished from the earth) and only fossil skeletons and tracks are left to record the fact that there were dinosaurs.

       No one truly knows why the dinosaurs died out, but paleontologists have developed some theories that we should know about. Now let us examine some of these explanations. One paleontologist thinks that diseases could have wiped out all the dinosaurs. Other paleontologists disagree with him and say that they don't believe that diseases would have killed every dinosaur in every part of the world.

       Another suggestion is that the early mammals that were developing at that time could have fed on dinosaur eggs. If the early mammals had eaten all the dinosaur eggs, then there would have been no new little dinosaurs to hatch. Although we know that Protoceratops laid eggs, we can't be certain that all the dinosaurs did lay eggs. Not all the reptiles living today are egg-layers. Another weakness of this theory is the assumption that all the early mammals ate eggs.

       Most paleontologists are able to agree that change in climate is an important clue to the disappearance of the dinosaurs. When dinosaurs lived, the landscape looked quite different than it does today. There were many lakes and swamps with mosses, ferns, and water plants. Great subtropical forests flourished, and palm trees grew in Colorado and Wyoming. The climate was more nearly uniform all over he world than it is now - there were not the hot summers and cold winters of today. Then very slowly the continents were raised, the swamps and lakes were drained, and mountains were pushed up in many parts of the northern hemisphere.

       With these changes in the climate and in the land came changes in the kinds of vegetation. Evidently the dinosaurs were not able to accustom themselves to all these changes in their surroundings and gradually began to die off. Probably the stegosaurs were the first of the dinosaurs to become extinct. Then gradually the giant plant-eating dinosaurs, the meat-eating dinosaurs, the duck-billed dinosaurs, the armored dinosaurs, and the horned dinosaurs followed into extinction. As the plant-eaters gradually became fewer and fewer, the meat-eaters must have also diminished in number because their source of food, the plant-eaters, had become scarce. The meat-eating dinosaurs may have helped to hasten their own extinction by becoming dinosaur-cannibals.

       Paleontologists believe that the dinosaurs became extinct as the result of several causes. A diminished food-supply and the inability to become adapted to a changing world were among the important factors. With the dinosaurs disappearing, the small active mammals began to dominate the scene. But we must not get the idea that the dinosaurs died off within a few years. Paleontologists tell us that the time of the great dying‚ lasted for millions and millions of years. But these are only scientific theories.

       As the days of the dinosaurs dimmed, many other animals became extinct. Some of these were the flying reptiles (pterosaurs), among which one giant had a wing-spread of twenty-five feet; the swimming reptiles (ichthyosaurs), which were ten or more feet long and looked much like the porpoises of today; the marine lizards (mosasaurs), thirty or more feet long; the swimming reptiles (plesiosaurs), with incredibly long necks; the large marine turtles (protostegids); and, among the invertebrates, the shelled mollusks (ammonites).

What really killed the dinosaurs? BBC Earth.