Dinosaurs: A Fully Illustrated, Authoritative and Easy-to-Use Guide

by Eugene S. Gaffney, John D. Dawson (Illustrator)

Overview

This eBook is best viewed on a color device.

Dinosaurs have long been a source of speculation. This beautifully illustrated guide includes:

- Fascinating facts about these animals that ruled the earth for more than 100 million years

- Key features that make each individual genus distinctive

- The latest information about how dinosaurs evolved and why they became extinct

Dinosaurs is an indispensable reference for everyone intrigued by these mighty creatures.

Product Details

ISBN-13:	9781466864665
Publisher:	St. Martin's Press
Publication date:	02/25/2014
Series:	A Golden Guide from St. Martin's Press
Sold by:	Macmillan
Format:	eBook
Pages:	160
File size:	25 MB
Note:	This product may take a few minutes to download.

About the Author

Golden Guides first appeared in 1949 and quickly established themselves as authorities on subjects from Natural History to Science. Relaunched in 2000, Golden Guides from St. Martin's Press feature modern, new covers as part of a multi-year, million-dollar program to revise, update, and expand the complete line of guides for a new generation of students.

Eugene S. Gaffney contributed to nature guides from Golden Guides and St. Martin's Press.
John D. Dawson contributed to nature guides from Golden Guides and St. Martin's Press.

Read an Excerpt

CHAPTER 1

DINOSAURS

For the entire length of the Mesozoic Era, more than 150 million years, dinosaurs were the dominant type of four-legged animals. Dinosaurs were very successful, hundreds of different kinds evolved, and they lived in many different land habitats.

The word dinosaur means "terrible lizard" and was coined by a British scientist, Sir Richard Owen, in 1842. Fossil teeth and bones were being discovered that indicated a gigantic form of extinct animal. The popular idea of dinosaurs as gigantic, ill-adapted monsters isn't very different from what it was in Owen's day. But after more than 100 years of discovery and study, we now have more accurate ideas aboutdinosaurs. Certainly most were gigantic and monstrous, but many were small and active, and some are still alive today as birds. Dinosaurs were so well adapted that they survived for hundreds of millions of years and evolved a bewildering variety of structures. Although we know something about the forms of their skeletons and their evolutionary relationships, the behavior and biology of the extinct dinosaurs is an elusive topic prone to speculation and controversy. Trackways (here and here), burial environments (hereand here), skin impressions (here and here), fossils of juveniles (here, here), and other sources provide clues to dinosaur habits, but unanswered questions greatly outnumber well-supported solutions.

CHAPTER 2

DINOSAUR DISCOVERIES

Dinosaur bones had been found for hundreds or perhaps thousands of years before Sir Richard Owen named them. But as with so many aspects of the earth's natural history, information about dinosaurs came gradually and irregularly.

Emergence of critical attitudes in science in the 18th and 19th centuries prompted new ideas about fossils, and dinosaurs began feeding controversies about extinction and evolution. Such 19th-century paleontologists as Georges Cuvier, William Buckland, and Gideon Mantell promoted the idea of comparing fossils with recent animals. They observed that fossil limbs and teeth were similar to those of recent reptiles and mammals but that there were significant differences as well.

By the middle of the 19th century, fossils had provided evidence that vast groups of animals had become extinct and that these animals were similar in many ways to recent animals. Dinosaurs were interpreted as evidence that life evolved, or changed. Beginning in the second half of the 19th century, intensive efforts were undertaken to discover more specimens.

Sir Richard Owen's reconstructions of such dinosaurs as Megalosaurus were based on only a few bones and later required many changes. In Philadelphia, Joseph Leidy and Waterhouse Hawkins mounted the first dinosaur skeleton, Hadrosaurus, in 1868. Although they had more bones than Owen did, their skeleton was still incomplete. The real advance of knowledge about dinosaurs awaited the discovery of nearly complete and well-preserved specimens.

The dinosaur fields of western North America were discovered in the latter part of the 1800s, and other rich dinosaur finds were made in Central Asia, East Africa, and Europe. It was the western North American collections, however, unearthed in a period from about 1890 to 1920, that yielded most of the well-preserved dinosaur specimens known today.

MORE EVIDENCE A breakthough came in 1878, when a rich deposit of the Early Cretaceous dinosaur Iguanodon was discovered in a Belgian coal mine. After great difficulties in collecting and preserving this material, the first mounted Iguanodon skeleton was exhibited in 1883. The final collection, exhibited in Brussels today, consists of 11 free-standing skeletons and 20 others mounted in their original positions.

The discovery of vast fossil fields in western North America soon eclipsed the Belgian finds and attracted Barnum Brown, the Sternberg family, Earl Douglass, and other legendary dinosaur hunters. The years 1900 to 1915 were the "golden age" of dinosaur collecting, resulting in finds that filled the great dinosaur halls of North America. These are the source of our current ideas about dinosaurs.

WHERE DINOSAURS HAVE BEEN FOUND

Most of the major dinosaur discoveries are shown on this map. The absence of dinosaurs in Antarctica may be due to poor exposures and difficulties of collection rather than to actual absence of fossils. New discoveries of duck-billed dinosaurs and meat-eating dinosaurs in the North Slope of Alaska show that there is still a great potential for new localities that extend the range and the environment of dinosaurs.

GEOLOGIC TIME

The earth is probably 4 to 5 billion years old. Precisely when life first appeared on earth is not known, but the oldest fossils are more than 3 billion years old. The early fossil record of life is sparse, and fossils are not common until the beginning of the Cambrian Period about 600 million years ago. The first land vertebrates appeared in the Devonian Period about 410 million years ago. Dinosaurs and mammals both appeared as fossils at about the same time — in the Triassic Period about 250 million years ago. For the next 185 million years, dinosaurs flourished while the mammals remained inconspicuous. Mammals did not become greatly diversified until the extinction of the dinosaurs some 65 million years ago.

The time scale shown on the next page is based on a combination of the following two methods of dating.

RADIOMETRIC DATING The rate of decay, or breakdown, of certain radioactive elements is constant, and by carefully measuring the products and comparing them with the remaining amount of the original element, the precise date of formation of the element can be accurately determined. However, radioactive elements are not common in fossil-bearing sediments. They are more common in volcanic or other igneous rocks.

CORRELATION of rocks in one place with rocks of the same age in another place is the second method of dating fossils. Though by far the most common method, this determines only relative rather than absolute age. Correlation is often done with fossils, based on the assumption that specimens of the same or closely related species lived at the same time. By using the principles of correlation, many fossil deposits that lack radioactive elements can be dated.

HOW DINOSAURS WERE PRESERVED

Dinosaurs and other animals we know only as fossils were buried and preserved by natural processes, then later exposed and found. Most well-preserved dinosaur fossils are found in what were large river systems, similar to the present-day delta region of the Mississippi River.

Large rivers carry great quantities of mud and sand, eroded from uplands. Much of the mud and sand is deposited offshore, but large amounts are also deposited on the banks of the river system as it forms branches and meanders back and forth.

Animals living in the flood plain may fall into the river during times of flooding. Sometimes skin imprints are left, but the soft tissues rot, leaving the bones buried in the mud or sand. Minerals may invade the bone cell spaces, or the entire bone may be replaced. Later, uplifts or mountain building raise the now-consolidated sandstone or shale so that erosion by wind and water removes the old sediment. Parts of the skeleton are then exposed and become visible to the lucky collector.

1. Death of animal in or near an area that has rapid deposition of sand or mud, like a river

2. Soft tissues rot away. Skin imprints may be formed if the deposition is very rapid.

3. Burial by sand or mud

4. Mineralization of bones by dissolved chemicals in ground water

5. Uplift of rocks containing fossils, and erosion, expose bones.

COLLECTING DINOSAURS

Fossil hunters begin looking where there are lots of exposures of rocks old enough to contain dinosaurs. Fossil bones are usually found when fragments are seen scattered on the surface of the ground. Rarely do fossil hunters go to a place and start digging before seeing an exposed bone.

The extent of the bone or skeleton is determined by using small picks and shovels. Usually there is only one bone or a part of a bone. Seldom found are connected, or articulated, bones or a partial or complete skeleton. Even more rarely are many skeletons found.

Bone surfaces are generally fragmentary and need to have dilute glue, shellac, or resin painted over them. At this stage bones may be covered with moistened tissue or newspaper to fit into cracks and spaces. This is the most time-consuming part of collecting fossils and requires the most skill.

Cracks make it possible to divide the skeleton or bone into manageable units. These units are further separated by trenching; some undercutting may also be done. Each unit can then be wrapped, using plaster-soaked cloth or plaster bandages. The bone is usually protected from the plaster by newspaper.

The plaster bandages are wrapped around the blocks as tightly as possible and are also placed on top. When completely set and hardened, the block is further undercut and finally turned over. If the job is successful, no bone sticks out of the bottom, and nothing falls out.

Blocks are left as is or are wrapped completely in plaster bandages, cloth tape, or rope for shipment to the preparation laboratory. Very hard rock, very soft rock, thick overlying rock, or water can make these simple tasks nearly impossible. Rocksaws, jackhammers, backhoes, bulldozers, and other tools can help, but too little money and too much isolation may prevent their use.

EXHIBITING DINOSAURS

Dinosaur skeletons are great attractions in natural history museums. Some of the earliest were mounted even though they were relatively incomplete, but the majority of specimens now in major museums are nearly whole skeletons.

In early mounts, metal pipes were used to support the great weight. The metal was bent and contoured to fit the bones as inconspicuously as possible. In panel mounts, the skeleton was embedded in a mesh or frame covered by plaster. Today a common trend is to exhibit high-quality fiberglass and plastic casts of skeletons. Such casts allow museums to put together a large hall of dinosaurs even when they have few actual specimens of dinosaurs of their own. Unfortunately, this trend deprives the public of new, real specimens, an essential ingredient in keeping the science healthy.

CHAPTER 3

WHAT DO WE REALLY KNOW ABOUT DINOSAURS?

There are various types of dinosaur fossils, but the most common is bone. Bone is made of stringlike protein fibers, collagen, that provide a network, or matrix, in which a hard mineral, apatite, is deposited. When an animal dies, the protein fibers decay and are lost. A fossil bone forms when the animal is buried by some natural event, such as mud or sand flowing over it in a stream. Although the collagen fibers are lost, the mineral is preserved, keeping the form and shape of the bone as it was. In a process not well understood, other minerals are usually added to the original apatite, filling in the spaces and making it heavier.

Because the process of burial usually damages bones and scatters them, complete skeletons with all the bones in their proper position are rare. Nonetheless, many skeletons have been found, and they form the main body of information about dinosaurs. Complete skeletons reveal a great deal about the size and shape of an animal, and leave little doubt about general features. Specimens have also been found in which skin and muscle imprints yield information about soft tissues. Very rarely, fine sediment buried a dinosaur before decay of the skin and muscles took place. Such specimens show the texture and form of the skin, and reveal that dinosaurs had a pebbly, patterned surface rather than overlapping scales, as in recent lizards and snakes.

The habitats of dinosaurs — whether they lived in swamps or grasslands, in forests or along beaches — cannot be determined directly from the location of a fossil skeleton. The only direct evidence a skeleton gives us about where the dinosaur once lived is the place of its burial, and animals are not always buried where they lived.

Dinosaur diet and locomotion are often better understood, but again, there is much speculation and little hard evidence. One specimen of a duck-billed dinosaur is known with stomach contents preserved, but the diet of other dinosaurs must be guessed at by comparing their teeth and feeding mechanisms with recent reptiles and mammals in the hope that similar teeth are correlated with similar diets. Again, general ideas can be developed. For instance, sharp, pointed teeth usually indicate meat eaters. But we cannot tell from this feature alone whether the animal was a predator, or whether it was a scavenger, feeding on dead carcasses.

Skin color, vocal sounds, social behavior, migratory habits, and interaction between species are all subjects we would like to know something about. It is useful to make intelligent speculations about such matters and to examine the fossil record to test our ideas. But the nature of fossils imposes severe restrictions on the type of information that can be learned, and many interesting questions cannot be answered.

WERE DINOSAURS WARM-BLOODED?

The chemicals inside animals that produce all the reactions and processes necessary for life will only function within certain temperature limits. If an animal becomes too hot or too cold, it will die. Animals have evolved various mechanisms to maintain their temperature limits.

Living reptiles tend to control their temperature by modifying their behavior. They are commonly called "cold-blooded" because they depend on their surroundings for temperature control, and may become slow moving or inactive during cool spells.

Mammals and birds, on the other hand, tend to use chemical mechanisms to maintain optimum temperature — producing internal heat (and cooling) irrespective of outside temperatures. Mammals and birds are often called "warm-blooded" because of this.

However, the temperature adaptations of animals are extremely complex, and it is inaccurate to say that an animal is either completely "warm-blooded" or completely "cold-blooded."

Nevertheless, some paleontologists have argued that dinosaurs were "warm-blooded" like mammals and birds. Most of the evidence for this idea is related to the fact that the skeletons of dinosaurs have many features seen only in active and fast-moving animals. According to this argument, dinosaurs must have been "warm-blooded" in order to maintain high-activity levels. Additionally, microscopic studies of bones suggest that dinosaurs grew rapidly and possibly had high-activity levels. However, none of this evidence is capable of showing the difference between permanent high-activity levels, as seen in most mammals, and temporary high-activity levels, as seen in most living reptiles. Furthermore, few paleontologists would defend the contrary notion that dinosaurs were overgrown lizards.

At present we may draw the following conclusions:

1. Dinosaur temperature control was probably very complex, as in living animals. "Warm-blooded" versus "cold-blooded" means little, because it is too simple.

2. Dinosaurs probably did not have lizardlike temperature control.

3. Available evidence cannot show that dinosaurs had either a mammalian or an avian (bird) method of temperature control. Neither can it show that they did not have such mechanisms, or that they had a peculiarly dinosaurian method about which we know nothing.

HOW ACCURATE ARE DINOSAUR RECONSTRUCTIONS?

Even with a complete, nicely articulated dinosaur skeleton with skin imprints, a wholly objective reconstruction of the living dinosaur isn't possible. Two assumptions must be made.

First, it is necessary to assume there are no problems with the skeleton and the degrees of movement of the articulated bones. In general, this isn't a serious difficulty, although it's been shown in recent years just how hard it is to choose among widely differing stances, tail postures, and even whether a dinosaur was bipedal, quadrupedal, or both. For example, some have argued that sauropods dragged their tails, while others have claimed the tails were held erect and could even be curled. Whether a ceratopsian had sprawling or erect forelimbs has been debated. In the absence of well-preserved specimens, the exact position of bones in the living animal is open to variable interpretations.

Secondly, the restoration of muscles requires the assumption that near relatives of dinosaurs, namely recent birds and crocodiles, have muscle patterns and attachments not very different from dinosaurs. This is difficult to test, because even the presence of muscle scars and attachments can be misleading when dealing with bones very different from the living model. Combining a "reasonable" amount of guesswork (something that differs widely among those who study dinosaurs) and a thorough knowledge of recent animals can result in a "best guess" reconstruction.

(Continues…)

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Excerpted from "Dinosaurs"
by .
Copyright © 1990 St. Martin's Press.
Excerpted by permission of St. Martin's Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.

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Table of Contents

DINOSAURS,
DINOSAUR DISCOVERIES,
Where Dinosaurs Have Been Found,
GEOLOGIC TIME,
HOW DINOSAURS WERE PRESERVED,
COLLECTING DINOSAURS,
EXHIBITING DINOSAURS,
WHAT DO WE REALLY KNOW ABOUT DINOSAURS?,
Were Dinosaurs Warm-blooded?,
How Accurate Are Reconstructions?,
Dinosaur Dimensions,
Dinosaur Diversity,
EVOLUTION OF ANIMALS WITH BACKBONES,
Key Characteristics,
EVOLUTION OF THE RULING REPTILES,
CHARACTERISTICS OF DINOSAURS,
Dinosaur Brains,
Dinosaur Tracks,
THE TWO MAJOR GROUPS OF DINOSAURS,
SAURISCHIAN DINOSAURS,
Giant Dinosaurs and Their Kin,
Meat-eating Dinosaurs,
Birds Are Dinosaurs,
ORNITHISCHIAN DINOSAURS,
Duck-billed Dinosaurs and Their Kin,
Horned Dinosaurs,
THE END OF THE DINOSAURS,
EVOLUTION OF THE MAMMALS,
CAREER OPPORTUNITIES IN PALEONTOLOGY,
DINOSAUR DISPLAYS,
MORE INFORMATION,
INDEX,