Viewmaster Booklet Reference Library by Mr Viewmaster
B676 Paleontology Prehistoric Life
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VIEW-MASTER REEL ONE |
Sample OCR of Viewmaster Booklet
| PALEONTOLOGY-THE
SCIENCE OF ANCIENT LIFE
What an immense, strange, and fascinating story is hidden in the rocks of the earth! They tell the history of the development of life, written in the fossilized remains of ancient plants and animals. Paleontology, the branch of geology devoted to the study of these fossils, has used them as keys to unlock the mysteries of this vast, awe-inspiring past. As sedimentary rocks are laid down by erosion, successively younger rocks are deposited on top of older ones. Because life has continuously evolved from older, simpler forms to more complex ones, certain fossils found in each stage of the rock record existed only at that one time, and identify that period of earth history wherever they are found. This relative dating—arranging these rocks and their fossils in chronological order from youngest to oldest—is shown in the geologic column on pages 8 and 9 of this View-Master booklet. It took the coming of the atomic age and radioactive dating (1949), to provide an absolute dating system which could measure the length of prehistoric time, and its divisions, accurately in actual number of years. Carbon-14 dating measures the rate—called the "half-life —at which radiocarbon in all organic matter changes to nitrogen. Its rate of disintegration permits accurate dating for only 70,000 years. Other elements with a longer half- life, date the ancient rocks of the earth, Today we know that the earth is more than 4V2 billion years old—and that it was a mere 600 million years ago that life became abundant enough to leave more than just traces of fossils. The knowledge of this fantastic past is one of paleontology's greatest contributions to the world. VIEW-MASTER REEL ONE 1 PALEONTOLOGIST AT DINOSAUR NATIONAL MONUMENT Even the massive bones of a once-mighty monster like this dinosaur became fragile after a million years; a paleontologist needs a delicate touch and great patience to free such fossils from their hard stone matrix. One hundred and forty million years ago, during the Mesozoic Age of Reptiles, the rugged, uptiltcd mountains and canyons around Dinosaur National Monument in Utah were flat, swampy plains with giant reptiles. Today their remains form one of the world's richest fossil beds. The Monument is a working field museum of paleontology, where visitors can watch specialists at work. FOSSIL BONE BED, MIOCENE EPOCH Like three jigsaw puzzles dumped into one pile, this fos- sil bone bed contains three different animals—a Chalice- there (picture 18), giant pig, and a small rhinoceros. The paleontologist uses comparative anatomy to put all the pieces together again. All animals have similar skeletal structures because all evolved from the same remote ancestor. At the same time, natural selection modified each class of vertebrates—fish, amphibians, reptiles, mammals, and birds, to fit its environment. The same is true of different species. An anatomist can tell immediately, from their skeletons, that the dog, man, and whale were all mammals; but he would never mistake the whale's flipper-shaped "hand" for that of a man. SPECIALIST RECONSTRUCTS A FRAGMENTED SKULL Birds ond mammals have similar bone structures, but proportions vary. White areas on the fossil skull were molded by this specialist to replace missing fragments. Reconstruction of missing parts, based on careful study of related living species as well as similar extinct types, is often necessary because skeletons can be scattered by carnivores (such as the saber-tooth tiger in the background), or unburied parts may be worn away by erosion. FLY IN AMBER (OLIGOCENE) Amber, the hardened resin from ancient trees, was prized in Greek and Roman times as jewelry. To the paleontologist, it is a fossil, for it contains completely preserved insects trapped ages ago in the sticky resin. ETC |