Loretta E. Ferrell, age 13, of Houston, Texas, for her question:
How do they know what the dinosaurs looked like?
The factual evidence includes bones, a few fragments or a complete skeleton, a few teeth, perhaps a claw and, with luck, an imprint of a patch of skin. From such scanty fragments, a skilled paleontologist can reconstruct a complete dinosaur and even describe the world he lived in.
Fossilized remains of past animals are buried in surface rocks and people have been finding them for ages. Mysterious bones suggested giants and griffins, dragons and other monsters. These early fossil discoveries led to the invention of many mythical monstrosities. Paleontology, the serious science of fossil study, got off to a bad start in the 17th century. Several fossil hobbyists began assembling groups of ancient bones without knowing much about nature's basic structure of skeletons.
The results, to say the least, were weird and wonderful. In one example, a long horn, a set of ribs and an assortment of smaller bones were misassembled to form an impossible skeleton. The fossils most likely came from several unrelated animals but the experts of the day hailed it as the remains of a unicorn. Fossil buffs competed, debated and argued over their unlikely specimens. Meantime the accumulation of fossil evidence grew and gradually more sensible theories won out and the truth prevailed.
The sound science of paleontology began in the 18th century and from the start it has been a science of comparisons. .~A fossil specimen is compared with animals of the present and known animals of the past. Its bony skeleton is assembled according to nature's patterns in similar animals. A completed skeleton of a giant dinosaur is a blueprint of information. It reveals the size and general shape of the huge animal.. A chalk line around its outer edges would give the outline of his shadow.
A shadow, of course, does not tell us very much about the living dinosaur. The paleontologist goes to other sources to fill in the details. From general biology, he knows the size and the shape of the muscles needed to move each large and small bone in the massive skeleton. He can describe the outer flesh of the dinosaur body. The final details are added from information gathered from similar specimens.
Many dinosaurs left their footprints in hardened shales, a few left imprints of their scaly skins. As a rule, a paleontologist is content to let his fossil skeleton stand on its own. But chances are, he has enough evidence to describe the claws and teeth, the skin and other surfacedetails of his specimen. An artist can use this data to paint a picture of the living dinosaur, just as he walked the earth, perhaps 100 million years ago.
If the first dinosaur skeleton had been unearthed only last week, a detailed reconstruction of the monster would be impossible. Our knowledge of the dinosaurs depends upon masses of information gathered from many parts of the world. Scraps of information are filed and compared with every new specimen. Information also is gathered from past geological history. A fossil is dated by the rocks around it. The same rocks also reveal whether he lived in a swamp or a desert and neighboring fossils often belong to larger and smaller animals that lived at the same time.