Introduction What is a Dinosaur Dinosaur History Maryland Dinos Dinosaur Worlds
Bone Hunting What Happened references Map Sources Suggested Readings
Previous page in Book Table of contents Next page in book


Many people wonder what became of this important group of animals that dominated the earth for some 160 million years. Did they all disappear without descendants, or are they still with us in some form? The traditional view is that they, along with more than half of the animal life on earth, became extinct at the end of the Mesozoic Era as a result of some single or group of catastrophes.

Several hypotheses have been advanced to account for this extinction, but in recent years some scientists have been claiming evidence that an asteroid or comet collided with the earth at the end of the Cretaceous Period. The impact may have caused so much dust and smoke to enter the atmosphere that the sun was obscured for a time, producing a pronounced cooling and interruption of vegetative growth. The result was the rapid extinction of the dinosaurs, according to the theory. Other scientists view this scenario with caution, contending that other factors forcing climatic change may have played a role in the extinction. That an important extinction did occur is agreed upon; in fact, this extinction defines the end of the Mesozoic Era. It is worth noting that extinctions are the rule in nature. More than 99 percent of all the species that ever lived are now extinct.

Paleontologists generally agree that dinosaurs and birds are closely related because they share many common anatomical features. Birds have dinosaur ancestors. In a sense, then, the birds are their true descendants.

Table of contents Previous page in book Next page in book