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Title: Dinosaur National Monument, Colorado-Utah - The Dinosaur Quarry
Author: Stucker, Gilbert F., White, Theodore E., Good, John M.
Language: English
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Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

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    [Illustration: Department of the Interior · March 3, 1849]

                      Fred A. Seaton, _Secretary_

                         NATIONAL PARK SERVICE
                      Conrad L. Wirth, _Director_

              For sale by the Superintendent of Documents,
                    U. S. Government Printing Office
                  Washington 25, D. C. Price 25 cents

                              THE DINOSAUR
                       DINOSAUR NATIONAL MONUMENT
                          _Colorado_ · _Utah_

      _By John M. Good, Theodore E. White and Gilbert F. Stucker_

    [Illustration: Apatosaur in Swamp]

         NATIONAL PARK SERVICE    ·    Washington, D. C., 1958

_The National Park System, of which Dinosaur National Monument is a
unit, is dedicated to conserving the scenic, scientific, and historic
heritage of the United States for the benefit and enjoyment of its

    [Illustration: National Park Service · Department of the Interior]


  THE QUARRY                                                            2
  THE DINOSAURS                                                         3
      First Discoveries                                                 3
      Position of Dinosaurs Among Reptiles                              4
      Geologic History                                                  4
      What They Looked Like                                             6
      Temperature Tolerance                                            10
      Gizzard Stones                                                   11
      How Do We Know?                                                  14
  ANIMALS FROM THE QUARRY                                              15
      Why So Many?                                                     19
      How Were They Preserved?                                         21
      How Were They Exposed?                                           24
  WHY DID DINOSAURS BECOME EXTINCT?                                    25
  HISTORY AND DEVELOPMENT OF THE QUARRY                                26
      Discovery and Early Years                                        26
      Starting the Quarry                                              28
      Extent and Development of the Find                               28
      Work Methods                                                     32
      Further Development                                              34
      Protecting the Quarry                                            35
      Present Development                                              37
  THE SCENE TODAY                                                      38
  KEY TO PRONUNCIATION                                                 46
  SUGGESTED READINGS                                                   47


    [Illustration: Spade and Pick]

As you approach Dinosaur National Monument from Jensen, Utah, you see
the mass of Split Mountain and the deep, short canyons that scar its
south slope near the Green River’s gorge. As you cross the National
Monument boundary the grand view is lost and you begin to notice
details. The masses of gray shale that seem to be carelessly piled
against the tilted sandstone layers are bare of vegetation. The ground
between the hills and the Green River is covered with sagebrush and
greasewood, while along the river itself are a few large cottonwood
trees and many bushes. A sharp turn brings a change of scene as your car
enters a portal in the wall you have been following. The pronounced tilt
of the rocks becomes more obvious.

A final steep climb and the visitor center is at hand. This building
encloses a significant part of the Dinosaur Quarry, perhaps the greatest
deposit of fossil dinosaur bones known today. From this quarry have come
many of the dinosaur skeletons that are seen today in our great museums.
After parking, a short walk to the overlook on the southeast reveals a
splendid view of Split Mountain. Between that broad arch of eroded
sandstone and the quarry lie steeply tilted sedimentary rocks of various
compositions and hues. Buff and gray sandstones that weather into soft
shapes are separated by reddish-brown shale. Directly to the east is a
section of varicolored shale whose pastel pinks, reds, greens, grays,
and whites justify the name of “rainbow beds” that was given them by
geologists. In the upper part of this section are hard sandstone and
limestone layers that resist the erosive action of wind and water. They
stand higher than the softer shales and form hogbacks that rim Split

One of these layers can be traced across the ravine immediately east of
the parking area into the sandstone ledge that forms the north wall of
the visitor center. This is the famous Dinosaur Ledge.

                               The Quarry

The Dinosaur Ledge is famous because here the world’s greatest store of
fossil bones of these long extinct reptiles has been uncovered. Two
groups, or orders, of dinosaurs have been discovered, with a number of
different types or kinds somewhat related to each other within these
orders. From the fossil bones, scientists can tell that these creatures
varied greatly in size and habits of living.


Some were the size of chickens, others as big as horses, and others of
such gigantic size that no land animal alive today can compare with
them. Some were flesh-eaters as indicated by the size and shape of their
teeth and their long sharp claws. Others were plant-eaters and again it
is the structure of their teeth and feet that tell us this. The
flesh-eaters were two-footed and walked on their hind legs, balancing
themselves with heavy long tails. Their short front legs were used as
clawed-arms for tearing at the flesh of other dinosaurs. Many
plant-eaters, on the contrary, were large, heavy, four-footed beasts,
often with long necks and tails. Many of the dinosaurs were land
dwellers, and many others lived in the great marshes and swamps of the
long Mesozoic (middle life) Era of the earth’s history.

Though the subclass of reptiles we call dinosaurs lived all through the
Mesozoic Era, those whose fossil bones have been uncovered in this
Dinosaur Quarry are embedded in a stratum of rock called the Morrison
formation. This rock stratum dates from the Jurassic Period in the
middle of the Mesozoic Era.

                             The Dinosaurs

                           FIRST DISCOVERIES

Today, most of us would recognize a fossil bone for what it is, but in
the 1790’s things were different. Isolated legbones, vertebrae, and
teeth of huge reptiles had been dug out of certain sedimentary rocks of
Europe and North America but their scientific importance was little

These specimens were found by people in all walks of life and it was
natural that their curiosity was greatly aroused. The finders took the
specimens to someone nearby whom they considered more competent to tell
them something about these strange bones and teeth. In nearly all cases
these “experts” were doctors of medicine. They studied the fossil
specimens and reported on them at regular meetings of the learned
societies of which they were members. It was customary to put the
fossils in the collections of these societies where they could be
studied by other members. In North America most reports of these early
discoveries are found in the _Proceedings of the American Philosophical
Society_ in Philadelphia, Pa.

By 1842 accumulated knowledge of these large reptiles was sufficient to
show that they were distinct from any group then known. This was first
recognized by Sir Richard Owen of the British Museum. It was he who
named the group _Dinosauria_. The name is made up of two Greek words:
_deinos_ (terrible) plus _sauras_ (lizard).

As knowledge of these unusual reptiles increased through the discovery
of additional types and more complete and better preserved specimens, it
became evident that dinosaurs were neither a single group of reptiles
nor were all of them large. Actually the dinosaurs show as much
diversity in size, body form, and habits as any group of reptiles. The
smallest dinosaur walked on its 2 hind legs like a chicken and was about
the same size. The largest walked on all 4 legs, was about 80 feet long,
and weighed 30 to 40 tons. As examples of variety in body form there are
the two-footed, flesh-eating _Antrodemus_, the armored _Stegosaurus_,
the turtle-like _Ankylosaurus_, the horned _Triceratops_, the huge
_Apatosaurus_, the two-footed vegetarian _Camptosaurus_, and the great
variety of head forms in the aquatic hadrosaurs. Although there were two
distinct groups, we still retain the term “dinosaur” as a convenient
name for all of them but qualify it by saying, flesh-eating dinosaur,
plant-eating dinosaur, armored dinosaur, etc., to indicate the
particular type we are talking about. Perhaps you are wondering how all
these ancient creatures are related to reptiles in general. Where do
they fit in the classification system devised to bring order to this
mass of knowledge?


It seems there are several orders of reptiles similar to and closely
related to the dinosaurs. Remains of these reptiles are found in the
sedimentary rocks which contain the earliest known dinosaurs. A number
of them resembled the dinosaurs but do not quite meet the requirements
as far as details of the skeleton are concerned. In the scheme of
classification these orders of reptiles are grouped together into the
subclass _Archosauria_. This subclass includes the dinosaurs,
crocodiles, and the flying reptiles. The lizards, snakes, turtles, and
the tuatera of New Zealand belong to other subclasses of reptiles which
have been distinct from that of the dinosaurs as far back in geologic
time as we can trace them. The kinship between the dinosaurs and the
small lizards living in the monument today lies only in that both are
reptiles. The only living relatives of the dinosaurs are the alligator
and the crocodile.

The dinosaurs were so numerous, and so dominated the whole of the
Mesozoic Era, that this period of earth history is frequently referred
to as the Age of Reptiles.

                            GEOLOGIC HISTORY

The Mesozoic Era began some 200 million years ago and ended some 60
million years ago. Although many other animals lived during that era,
the dinosaurs were the dominant forms of animal life on land. The 140
million years of the Mesozoic are divided into geologic periods named
Triassic (the oldest), Jurassic, and Cretaceous (the most recent).
Continental deposits representing each of these periods have been found
in all parts of the world and on all continents. Dinosaur bones have
been found in these deposits—even in such far-away places as Australia
and the southern tip of South America. Only Jurassic dinosaurs have been
found at Dinosaur National Monument.

    [Illustration: _Coelophysis_—SMALL TRIASSIC DINOSAURS, FORERUNNERS

The oldest known dinosaurs are found in rocks of the Triassic Period.
The smaller of these were chicken-size and the largest were about as big
as kangaroos. All of these Triassic dinosaurs were two-footed. They can
be divided into flesh-eaters and plant-eaters, although none are
believed to have been particularly specialized in their food habits. In
general the flesh-eaters were small, agile, and had sharp teeth for
seizing and overpowering active prey. The plant-eaters were larger with
rather long front legs and small blunt teeth suited only to cropping
vegetation. These plant-eaters are believed to be the Triassic ancestors
of the giant marsh-dwelling dinosaurs of the Jurassic and Cretaceous

A greater variety of dinosaurs lived during the Jurassic Period than in
the Triassic. Both two- and four-footed types were present. The
flesh-eaters remained two-footed but increased in size. _Antrodemus_,
perhaps the best known, was much bigger than a kangaroo. The larger
plant-eaters weighed from 30 to 40 tons and all were four-footed. The
largest land animals, they lived on dry land and in the swamps that
formed an important part of the Jurassic landscape. The first of the
armored plant-eating dinosaurs, _Stegosaurus_, inhabited the dry plains.
There were also some smaller, kangaroo-size plant-eaters that were

A wide variety of dinosaur fossils has been found in the rocks of the
Cretaceous Period, the last of the Mesozoic Era. The huge swamp dwellers
still thrived. The flesh-eaters had evolved much larger types and
included 40-foot _Tyrannosaurus_, the largest that ever lived. All the
flesh-eaters walked on their hind legs as did their predecessors of the
Jurassic and Triassic Periods.

New and interesting dinosaurs were present among the flesh-eaters.
Horned forms, somewhat similar to the rhinoceros but much larger, were
common. Also common were the turtle-like ankylosaurs. Perhaps the oddest
and most interesting dinosaurs of the Cretaceous were the two-footed
hadrosaurs. These excellent swimmers had weird head shapes with
complicated skull passages and openings. They were a very successful
group and at least 15 different kinds are known from the Cretaceous
rocks of North America.

                         WHAT THEY LOOKED LIKE

Ideas about the external appearances of dinosaurs have been developed
after many years of work and study. They are a combination of the ideas
of several people who had studied different specimens of a single
species. Let us review briefly the materials and work necessary to
arrive at a reasonably accurate picture of the body form and external
appearance of these strange reptiles.

The first requirement for arriving at a good idea of the build and
physical attitude of an animal is a nearly entire skeleton. We cannot
have too much of the animal’s skeleton missing or we may make a serious
error. But if the left hind leg is missing and we have the right, we are
not seriously handicapped. However, if both hind legs are missing we
must restore them according to a similar animal whose hind legs are

After the nearly entire skeleton has been found it must be collected
with great care. This is a rather involved process and, for some of the
large dinosaurs, 2 or 3 months work may be required. The specimen is
first uncovered and the fossil bone is treated with a preservative such
as gum arabic, shellac, or one of the plastics. An accurate diagram of
the specimen as it lies in the rock is made on cross-ruled paper. A
trench 2 or 3 feet wide is then dug around the specimen. The depth of
the trench is determined by the width of the specimen and the nature of
the rock.


If the specimen is too large to take out in one piece, as most dinosaurs
are, it is divided into sections which are numbered serially as they are
taken out. Each section is bandaged in strips of burlap dipped in
plaster of Paris. After the plaster has set, the section is turned over
and the bottom is sealed with burlap and plaster. The section is labeled
with the appropriate number and the section and number are shown on the

When all of the sections have been bandaged and numbered they are packed
in strong wooden boxes and shipped to the laboratory.

The work in the laboratory is more involved than that in the field, and
extreme care must be exercised to be sure that the bones will be
undamaged. In most cases the bones have been broken by natural causes as
they lay in the rock before discovery. All the pieces of each bone must
be thoroughly cleaned and securely cemented together. This is a very
time-consuming task and for a large dinosaur like _Apatosaurus_ it
requires 3 men 4 or 5 years to complete the task.

After all of the bones are cleaned and cemented together the vertebral
column is laid out in its proper sequence on a sand table. Special care
is exercised to be sure that the vertebrae fit correctly with each
other. In this way the correct curvature of the vertebral column is
determined. The proper relationships of the hip bones and ribs to the
vertebrae, the shoulder blade to the ribs, and elements of the limb
bones to each other are determined in the same manner. All of this work
is necessary to correctly fashion the steel framework which will support
the skeleton when it is placed on exhibition. The results of this
careful work must be the framework of an animal which could, if living,
easily go through the normal activities of life such as securing food
and escaping enemies.

Now that the framework of an animal has been set up so that it could
move about if it had muscles, skin, and life, how do we know how large
the muscles were and where they were placed? It is necessary to have a
thorough knowledge of the muscles of a recent animal similar to the one
we are restoring so that we will know what we are looking for in the
fossil. The areas at which muscles are attached to bones are called
muscle scars and are identified by their rough surfaces. Often the
necessary information can be obtained from publications which usually
represent the work done by graduate students for advanced degrees. At
other times we must make our own investigation. Thus if we know what
muscle we are looking for and the size and shape of its muscle scar, we
can determine whether the muscle is a spindle-shaped mass or a broad

After we have determined the size and position of the muscles which
operate the limbs, head, and neck, we have a reasonably accurate idea of
the external form of the animal, but we still know nothing of the nature
of the skin which covered the body. Since dinosaurs were reptiles, we
are obliged to assume that they were covered with a scaly skin in order
to preserve the body moisture. None of the modern reptiles possess sweat
glands in the skin. If they did not possess a waterproof covering of
scales they would die in a few hours as a result of the loss of body
moisture by evaporation through the skin. It is possible that some of
the marsh dwellers like _Apatosaurus_ had naked skin which was, as in
the elephant, nearly an inch thick. The elephant does not possess sweat
glands but the outer half of its skin is composed entirely of dead cells
which form a covering as waterproof as the scales of today’s reptiles.

There have been only a few lucky finds of mummified dinosaurs which show
the impressions of the scales. We know that all lizards do not possess
the same type of scales, and therefore, by analogy, we cannot assume
that the dinosaurs did. Eventually, we will probably find that the
dinosaurs exhibited as great a variety of scale-types as do today’s
lizards. As yet we have found nothing in the fossil record which
indicates the color of the dinosaurs. Again, we can only assume that
they exhibited as great a variety of colors as do our lizards. So also,
we assume their body functions were somewhat similar to the reptiles and
other related animals we know today.



                         TEMPERATURE TOLERANCE

We know the body temperatures of reptiles vary with that of the air or
water in which they live, as they have no means of internal temperature
control. They are very sluggish when their body temperatures are low and
become more active as these temperatures rise, but only to a certain
point. If the body temperatures of reptiles become too high, they die in
a few minutes.

A group of physiologists from Columbia University spent nearly 2 months
in southern Florida experimenting on reptiles. They determined the rate
of rise of body temperatures of large lizards and alligators of all
sizes during exposure to the midday sun. As was expected, the smaller
the reptile the more rapid the rise in body temperature. Dinosaurs were
reptiles so we can make two assumptions: That their physiology was very
similar to that of living reptiles; and that the rate of rise of their
body temperatures from exposure to the sun would follow the principles
found for living reptiles.

By applying these principles to the dinosaurs, this group of scientists
calculated that if the great bulk of an _Apatosaurus_ were exposed to
the direct rays of the sun at an air temperature of 110° F. for 36 to 40
hours, its body temperature would rise only 1° F. Therefore, if these
calculations are correct, it is probable that the very size of the huge
dinosaurs operated to maintain a fairly constant body temperature.
Consequently, daily and seasonal temperature changes probably did not
affect the activities of the large dinosaurs. However, the activities of
the small ones may have been affected by the daily range in temperature.

                             GIZZARD STONES

For many years rounded stones with a very high polish have been found in
the sedimentary rocks which contain bones of extinct reptiles. The
polish on these stones is very much higher than could have been applied
by the action of water or wind. Some look as though they had been
polished by a jeweler. Since we cannot attribute this very high polish
to wind or water action, we must seek another agent.

    [Illustration: _Protiguanodon._ NOTE GIZZARD STONES INSIDE RIB

Just as chickens swallow fine gravel for their gizzards to aid
digestion, so it is thought that some large dinosaurs swallowed stones
for the same purpose. There is some evidence to support this idea.
Several specimens of a group of swimming reptiles, called _plesiosaurs_,
which swarmed the Jurassic and Cretaceous seas, have been found with
highly polished stones inside the rib basket. Also a mass of highly
polished stones was found similarly associated with one dinosaur,
_Protiguanodon_, in the Lower Cretaceous rocks of Mongolia.

On the other hand, no highly polished stones have been found associated
with the specimens in the Dinosaur Quarry or anywhere in the quarry. A
search of the many publications on dinosaurs has not turned up any
mention of highly polished stones being associated with any of the many
specimens found in North America. Thus the evidence which we have does
not permit us to say that the dinosaurs found in the quarry did or did
not possess gizzard stones.

           The Climate, Life, and Landscape of Jurassic Time

The geologists who attempt to reconstruct the geography and climate of
the Jurassic Period first gather all possible facts and try to fit them
together to form a logical pattern. The results are then examined for
weak points and an attempt is made to find field evidence throwing light
on these weak points. The final result represents the sum of our
knowledge at the time but is subject to change as new facts are
obtained. Thus the following outline represents present thinking that
may be changed somewhat by future studies.

The land for miles around the Dinosaur Quarry was a low-lying desert in
early Jurassic time. The mountains you see now had not yet been formed,
and the whole desert area lay close to sea level. Great restless sand
dunes drifted across this level land to form a blanket 700 feet thick.
As the earth’s crust sank, these dunes were covered by a long arm of an
arctic sea that extended southward along the present trend of the Rocky
Mountains across Canada, Montana, Wyoming, and Utah. Millions of years
later, in late Jurassic time, when the Morrison formation was deposited,
the area rose again and the stage was set for the dinosaurs.

Imagine if you can, the vast plains extending from Mexico to Canada and
from central Utah to the Mississippi River. To the west were high
mountains in the Great Basin region of Nevada and western Utah. From
these highlands flowed great sluggish streams that carried large amounts
of sand and silt. Since the plains were almost flat, swamps and small
lakes were probably numerous. The streams may have changed their courses
from time to time as they were not confined to deep valleys. When the
whole region emerged from the sea the climate became more humid.
Volcanoes were active far to the west; the winds carried clouds of
ejected dust eastward and deposited them on the plains. Semi-tropical
conditions probably existed throughout the United States and in parts of
Canada. These deposits are called the Morrison formation.

The warm humid climate provided ideal conditions for plant growth. Great
forests of lush vegetation covered the land. Many of these plants have
since disappeared, but some of their related species may be found today
in the tropics. Most of the plants of our Temperate Zone had not yet
evolved. However, there were tall stands of a type of pine, and other
evergreens. There were also gingkos and curious tree ferns.

Various herb ferns formed a ground cover as thick and lush as grass on a
well-watered prairie. Palmlike ferns resembling today’s cycads were
common, while along the river grew horsetail rushes like those living
today. Flowering plants of the Recent Epoch of geologic time (in which
we are now living) had not yet made their appearance. Thus the hardwood,
broadleaf forests of oak, elm, beech, maple, and similar trees were
absent. So too were the flowering shrubs familiar to the Temperate Zone.
Even the grasses were missing.

However, if you could picnic in this strange plant world you would soon
be slapping mosquitos and cursing the ants. For even in such ancient
times these insects were present; and so were a great variety of other
insects as is known from the more than 1,000 species that have been
discovered in Jurassic rocks. Among them were representatives of most
modern orders such as grasshoppers, beetles, moths, ants, and flies.
Jurassic insects probably looked much like those of today.

Among the most interesting of the strange reptiles were the pterosaurs
that dominated the skies. They resembled the modern bats in some ways
but their leathery wings were supported on each side by one finger
instead of four, and their skins were scaly or bare instead of hairy.
Some forms had long tails that were flattened at the tip and helped them
balance in flight, but others were tailless. Some pterosaurs were no
larger than sparrows while others had wing spans of 3 to 4 feet.

Crocodiles sunned themselves on the banks of sluggish streams and lakes.
They probably looked a good deal like those that live in modern swamps
and their habits were similar. Many a small dinosaur fell victim to
their stealthy attack and disappeared beneath the waters of some ancient

Birds have been found in Upper Jurassic rocks of Germany and may have
lived here too. Their fossil remains would probably have been classed as
reptiles had not feather imprints been a part of them. About the size of
crows, these reptile-like birds had small conical teeth, three-clawed
fingers on each wing, and a long tail instead of the fan of feathers
seen on modern birds.

Small mammals were also living at the time the Morrison formation was
being deposited and their remains have been found in the dinosaur quarry
at Como Bluff, Wyo. The largest ones were about the size of a house cat
but the majority were much smaller, probably about the size of today’s

We do not know much about the habits of these early mammals but they
were probably rather shy and retiring. This would be expected in the
world of giants where they lived. Some of them lived in trees and there
was one group whose skull characteristics resemble those of the rodents.
It is likely that these primitive mammals lived a life similar to that
of the rodents millions of years later.

This, then, was the setting, the stage upon which the dinosaurs played
their leading roles. Although we have restricted our discussion to
Morrison time in northeastern Utah, the same or similar animals lived
all over the world. Worldwide humid and mild climates produced a
similarity of plant and animal life during most of the Mesozoic Era
whose like has not been seen in the last 60 million years. It was a
strange world and ruled by strange animals, but it must have been an
interesting one.

                            HOW DO WE KNOW?

This is a good time to stop and try to explain that this story, of
plants and animals of the past, has a firm foundation in today’s
facts—it is not a fantasy.

The methods by which geologists and paleontologists have established the
age, climate, and life of Morrison time cannot be described for you here
in detail. To attempt such a description would require too much space
and would probably seem dull to most readers. Perhaps the best approach
is to describe some features and explain how they contribute to our

The rocks that were deposited here in Morrison time tell us much of the
story. The sandstones were once stream sandbars or perhaps beaches
around lakes. The shale, siltstone, and clay were muddy stream or lake
bottoms. The discontinuous ledges of conglomerate probably represent
gravel bars formed during flood stages or at places where the stream
currents were very swift.

Just rocks you may say—but look closely. A piece of sandstone contains
grains of sand that differ from each other in size, shape, and
composition. Frequently these characteristics point to the source of the
sandstone and tell something about the conditions at the time it was
deposited. Chunks of black material are examined closely and prove to be
charcoal—carbonized remains of plants.

Microscopic examination of clay fragments reveals shards of volcanic
glass and ash that speak of active volcanoes. Sometimes these clays bear
the carbonized imprints of delicate plants that long ago sank to the
bottom of some lake or stream where they were buried and fossilized.

The fossils themselves are most important in reconstructing conditions
of the past. We find the shells of fresh-water clams in the sandstones
with dinosaur bones. Crocodile bones are also common. We are reasonably
sure, then, that these deposits of sand and mud were formed in rivers
and lakes when the climate was mild.

We reason by analogy. For example, fossil plants and animals have
counterparts or descendants in the world of today. We assume, in the
absence of contrary evidence, that the fossil animals lived like their
present-day counterparts. Although no birds, mammals, or pterosaurs have
been found in this quarry, they were probably living here with the
dinosaurs. It is possible, in fact probable, that some modern animals
and plants live in different environments than did their Morrison
ancestors and relatives but we have no way of knowing which ones they
were. We can only take the data available, arrange them as logically as
possible, and continue the search for more. Some may scoff at such
methods of reasoning yet they do provide good results. What other
methods can be used when the world under investigation lies millions of
years in the past?

                        Animals from the Quarry

In the rocks of the Morrison formation at the quarry, both orders of
dinosaurs are found—_Saurischia_ and _Ornithischia_. Paleontologists
have divided the dinosaurs into these two groups on the basis of
important skeletal differences. These differences remain constant for
the orders and vary within each order only in small details.

The important structural difference in dinosaurs is found in the pelvis.
In all land vertebrates, the pelvis is made up of three pairs of bones
called the ilium, pubis, and ischium. The paired ilium is joined to each
side of the backbone and projects downward to meet the pubis and ischium
at the socket for the head of the thigh bone. The pubis forms the front
third and the ischium the rear third of this socket. In the order
_Saurischia_ the bones of the pelvis are arranged as in most reptiles
and mammals. In the order _Ornithischia_ the pubis extends backward
along the ischium as it does in the birds.

Two types of saurischian dinosaurs are found in the quarry.
_Antrodemus_, a flesh-eating type, was about the size of a horse, but
was two-footed. It had strong sharp claws on its feet. Its teeth were
about 2 inches long, flattened from side to side and with fine
serrations on front and back edges. Actually it is not known whether
_Antrodemus_ overpowered and killed the large swamp-living dinosaurs, or
merely fed on their carcasses after they had died from other causes.
However, there has been found in the quarries at Como, Wyo., a partial
skeleton of _Apatosaurus_ with grooves on the bones which suggest tooth
marks. The spacing of these grooves fit the spacing of the teeth of a
specimen of _Antrodemus_ found in the same quarry.


The plant-eating dinosaurs of the order _Saurischia_ which are found in
the quarry were all four-footed. They had bodies about the size of an
elephant or larger. The principal differences between the flesh- and
plant-eating dinosaurs were the length of the neck and tail, the details
of their skull structure, and other parts of their skeleton.

_Apatosaurus_ is perhaps the most familiar dinosaur to most of us. Its
hind legs were much longer than its front ones and gave the animal a
high-hipped, stooped appearance. _Apatosaurus_ was about 70 feet long
and probably weighed close to 40 tons. _Diplodocus_ was longer (one of
them 75½ feet) but was slender and lightly built. Its neck was longer
and it had a whiplash tail that looked much like the tail of the modern
whiptailed lizard. _Diplodocus_ also had long pencil-like teeth
different from those of any other known dinosaur. _Barosaurus_ has an
extremely long neck with long individual neck bones. Two members of the
genus _Camarasaurus_ are similar to each other except for size; one was
small, but the other was as large as _Apatosaurus_. _Camarasaurus_ had
longer front legs than _Apatosaurus_ and was generally better

    [Illustration: _Antrodemus_, THE FEROCIOUS CARNIVORE OF MORRISON

    [Illustration: THE GREAT SAURISCHIAN PLANT-EATER _Apatosaurus

Fossils of the saurischian plant-eaters are found much more frequently
than those of flesh-eaters and are usually in sedimentary rocks which
contain beds of clam shells. For this reason it seems probable that they
waded lagoons and streams, feeding on aquatic and bank-side vegetation.
The suggestion has been made that the larger dinosaurs could not even
walk on dry land because their weight would have crushed the bones of
their feet; they needed the buoyancy of water to help support them.
However, footprints of a huge dinosaur, much larger than any from the
quarry, have been found near Glenrose, Tex. The large footprints were
made on a sandy beach of a sea in Lower Cretaceous time. Thus we know
that they could walk on dry land if they wanted to.

All of the dinosaurs of the order _Ornithischia_ were plant-eaters, and
were of both two- and four-footed types. The two-footed types found in
the quarry are _Camptosaurus_, _Dryosaurus_, and _Laosaurus_. These
forms had well developed front legs, though much shorter than their hind
legs, which suggests that they may have dropped down on “all fours”
while feeding or resting. The teeth were small, chisel-shaped, and
fitted only for cropping vegetation. The larger specimens of
_Camptosaurus_ reached a length of 17 feet but _Laosaurus_ was only 2½
feet long.

_Stegosaurus_ is the only quadruped (four-footed) of this order found in
the quarry. It had long hind legs and very short front legs. It reached
a length of 18 to 20 feet and was 10 to 11 feet high over the hips. The
most characteristic feature of this form was the double row of bony
plates down the back and the group of spikes at the end of the tail. The
teeth were similar to those of _Camptosaurus_, but much more numerous.

Only two other groups of reptiles have been found in the quarry at
Dinosaur National Monument and their remains are rare. These are the
crocodiles and turtles. Two crocodiles are known; the larger one,
_Goniopholis_, was about the size of existing alligators and did not
differ in external appearance from present-day crocodiles. The smaller
one was less than a foot long and resembled a 2 weeks’ old alligator as
much as anything. However, we know from the texture of the surface of
the bone that it was not a young animal. The turtle, _Glyptops_, was
about the same size and general appearance as the pond turtles of today.

                              WHY SO MANY?

The partial skeletons of more than 20 individual dinosaurs and the
scattered bones of about 300 more have been discovered in the Dinosaur
Quarry. Many of the best specimens may be seen today at museums of
natural history in the larger cities of the United States and Canada.
The quarry is easily the largest and best preserved deposit of Jurassic
dinosaurs known today.

How and why did so many dinosaur skeletons accumulate here? How were
they preserved? These are among the common questions asked of park
rangers and naturalists at Dinosaur. The answer is a combination of
circumstances and luck.

Many people get the impression from the mass of bones in the quarry wall
that some catastrophe such as a volcanic explosion or a sudden flood
killed a whole herd of dinosaurs in this area. True enough this could
have happened, but it probably did not. The main reasons for thinking
otherwise are the scattered bones and the thickness of the deposit. In
other deposits where the animals were thought to have died together, the
skeletons were usually complete and often all the bones were in their
proper positions, or articulated. In a mass killing the bones would have
been deposited on the stream or lake bottom together at the same level,
but in this deposit the bones occur throughout a zone of sandstone about
12 feet thick. The mixture of swamp dwellers and dry-land types also
seems to indicate that the deposit is a mixture derived from different
sources. Rounded fragments of fossil bone have been discovered in the
quarry—fragments that attained their pebblelike shape by rolling along
the stream bottom.

If the mass of bones was not the result of catastrophe what did happen?
The quarry area is a dinosaur graveyard, not a place where they died. A
majority of the remains probably floated down an eastward flowing river
until they were stranded on a shallow sandbar. Some of them, such as the
stegosaurs, may have come from far-away dryland areas to the west.
Perhaps they drowned trying to ford a tributary stream or were washed
away during floods. Some of the swamp dwellers may have mired down on
the very sandbar that became their grave while others may have floated
for miles before being stranded.

Even today similar events take place. When floods come in the spring,
sheep, cattle, and deer are often trapped by rising waters and
frequently drown. Their bloated carcasses float downstream until the
flood recedes and leaves them stranded on a bar or shore where they lie,
frequently half buried in the sand, until they decompose. Early
travelers on the Missouri River reported that shores and bars were
frequently lined with the decomposing bodies of bison that had perished
during spring floods.

In Dinosaur National Monument, the positions in which partial skeletons
of the dinosaurs lie suggest that they decomposed on a sandbar. The
bones on the underside of a skeleton are often arranged as they were
when the animal was alive, while those on the upper or exposed side may
be scattered. Such scattering would be expected as the ligaments and
muscles holding the bones together decomposed; stream currents and
scavengers could then disperse them. Stream currents are suggested by
the position of the long, flexible tails and necks of the large plant
feeders. These, like streaming water plants in a river, trail downstream
to the east.

    [Illustration: _Camptosaurus_—AN ARNITHISCHIAN PLANT-EATER. (DRAWN

                        HOW WERE THEY PRESERVED?

The concentration and burial of dinosaur bones is only the beginning of
the fossil story. The combination of circumstances which operated here
was a common one and yet fossil quarries are rare. Why? The bones have
to be preserved and this seldom happens. The bones that are buried in
one flood are frequently unearthed and scattered by the next. Those that
are exposed to the weather usually disintegrate completely in a few
years. The bones in the Dinosaur Quarry did not.

Sometime after they were buried, the organic minerals of the bones were
more or less completely replaced by minerals of inorganic origin such as
silica. No one knows exactly why or how this happened, but it did. Most
geologists think this replacement process occurs when subsurface or
ground water containing soluble and colloidal minerals dissolves a
molecule of the bone and immediately replaces it with a new mineral.
Roughly such a process is like removing red bricks from a house and
substituting yellow. When the substitution is complete, the house still
has the same dimensions but it is composed of different materials. The
replacement was a faithful one, too, because microscopic structure of
the original bone was faithfully reproduced by the replacing minerals.

    [Illustration: ROAD MAP
    High-resolution Map]

Following Morrison time, thousands of feet of younger sediments were
deposited on the sandbar that contained the dinosaur bones. The whole
sequence of sediments was compacted into rock and some bones were
crushed and distorted.

                         HOW WERE THEY EXPOSED?

After the sediments became rock and the bones had probably been replaced
by stone (fossilized), this part of the world, which lay near or below
sea level for millions of years, began to rise. Great forces acted upon
the earth’s crust. These forces created faults, or fractures, in the
rock crust along which movement occurred. And what had once been sea
bottom was moved upward and became lofty mountains. This titanic change
has been called the Laramide Revolution; it closed the Mesozoic Era with
the formation of the Rocky Mountains.

    [Illustration: _Stegosaurus._ AN ARMORED DINOSAUR OF THE JURASSIC

Although the effects of the Laramide Revolution were not as profound at
Dinosaur as they were east of it, they were quite important. The rocks
were lifted to form the southwest flank of Split Mountain—a small arch,
or anticline, on the south side of the Uinta Mountains. This mountain
building explains the pronounced southward tilt of the Dinosaur Ledge
and other rock layers visible in the quarry area. As the land rose,
streams flowed more rapidly, cutting deeper into the rocks and carrying
away the debris. Gradually thousands of feet of this debris—shale,
sandstone, and clay—were stripped away through erosion.

Finally all the material on top of the Morrison sandbar weathered away.
Some 140 million years after burial the fossil bones were exposed by the
agent that had buried them so long ago—running water! All that remained
was for them to be found, and that was the luckiest chance of all. Just
suppose they had been uncovered a million years ago—only a second in
geologic time. No one would have been present to discover them, and
through the years they could well have crumbled into dust and been blown

                   Why Did Dinosaurs Become Extinct?

At Dinosaur National Monument only Morrison rocks of the upper Jurassic
Period contain the fossil bones of dinosaurs. After Morrison time, the
Cretaceous seas invaded this area. More than 5,000 feet of sandstone,
shale, and mudstone were formed from sediments deposited in these seas.

Elsewhere in North America and the rest of the world, the diversity and
numbers of dinosaurs actually increased. Entirely new groups evolved and
achieved success in the battle for survival. The climax of reptile
development seems to have come near the end of Cretaceous time in the
Mesozoic Era. As the dinosaurs ruled the continents, so did other
strange reptiles dominate the seas. Had you been able to see this
ancient world, you would surely have been convinced that the dinosaurs
and other reptiles would rule forever.

But it was not to be. The dinosaur hordes were wiped out and the
reptiles reduced to the position of relative insignificance they occupy
today. Such a profound and sudden change in the evolutionary trend of
life must have had a cause, and scientists have sought it. Several
theories have been proposed to explain extinction of dinosaurs, and they
are most interesting.

At the end of Cretaceous time, some of our great mountain ranges were
formed. It was a time of earthquakes and of volcanoes that belched forth
clouds of ash and rivers of molten rock. Some people would say these
catastrophic events killed all the dinosaurs. The scientist shakes his
head. If these events killed dinosaurs, why not the other animals that
lived with the dinosaurs. And what of those parts of the world that had
no volcanoes, what killed dinosaurs there?

Changes in environments, the drainage of lakes and swamps as young
mountains rose, changes in vegetation as new plants replaced old, and
sudden shifts of climate occurred. These conditions could explain local
extinction, but there were places where these changes did not occur and
yet all dinosaurs in all places died.

A one-time favorite theory suggested that increasing numbers of small
mammals ate dinosaur eggs, but there were many mammals eating dinosaur
eggs during all of Cretaceous time and the dinosaur hordes increased.
Many more mammals during succeeding ages have not killed off the
turtles, snakes, lizards, and crocodiles that lay eggs and exist in
great numbers today.

Some disease or combination of plagues may have swept the dinosaurs into
extinction. If so, no evidence has been found to date that confirms or
denies. However, most paleontologists do not accept this theory.

These are some of the theories that have been advanced to explain the
sudden extinction of dinosaurs throughout the world. Each theory will
explain the death of some dinosaurs in some places but attempts to apply
any of them, or combinations of them, to worldwide extinction have

This dinosaur story is like a mystery thriller with the last pages torn
out. A most important part is missing. That is true and the
paleontologist knows it. He also knows the riddle will probably never be
solved. He might point out, however, that no one has successfully
explained the extinction of the passenger pigeon which occurred quite
recently, nor do we know why some other species of wildlife are on the
brink of extinction today. The paleontologist is not the only one who
must say, “I don’t know.”

                 History and Development of the Quarry

                       DISCOVERY AND EARLY YEARS

No one knows how long the old bones had been weathering out of the hills
of what is now Dinosaur National Monument before the first man saw them.
Curious Indians, wandering between the upturned ridges of Mesozoic
rocks, picked up fragments and carried them off to their camps where
they are now found among the arrow points, ax heads, and corn-grinding
stones. In 1776, the Spaniard, Father Escalante, passed within sight of
today’s dinosaur quarry, not dreaming of the antiquity hidden there.
Maj. John Wesley Powell, on his second voyage down the Green River in
1871, recorded the presence of “reptilian remains” in the area, but
wrote nothing more about them. Sheepherders, cattlemen, and hunters
observed them and were impressed in proportion to their understanding.
But, through all the years, the nature of the bones remained a mystery.


Then, in 1893, this mystery was solved. O. A. Peterson, a scientist from
the American Museum of Natural History, while conducting field work in
the Uinta Basin to the south of the present monument boundaries,
discovered bones out-cropping from a recognized fossil-bearing stratum.
The stratum was the 140,000,000 year-old Morrison formation. The bones?
Peterson reported them as the remains of dinosaurs.

That report was to have an important influence, 15 years later, in
directing a fellow paleontologist from the Carnegie Museum in Pittsburgh
to investigate the area. Earl Douglass was the paleontologist’s name. In
1908, he and W. J. Holland, Director of the Carnegie Museum, found
themselves in the region of Peterson’s discovery, searching for dinosaur
remains. They extended their search to the north and thence along the
Morrison hogback that flanks Split Mountain. Bone was found—not much,
but enough to bring Douglass back the following summer and in company
with George Goodrich, a local resident, to pursue the hunt.

The hunt came to a triumphant climax on August 17, 1909, when—to quote
from Douglass’s diary—“At last in the top of the ledge where the softer
overlying beds form a divide ... I saw eight of the tail bones of a
_Brontosaurus {Apatosaurus}_ in exact position.”

                          STARTING THE QUARRY

This was the beginning—the beginning of the celebrated dinosaur quarry
which was to yield such a multitude and variety of ancient forms to
science, and eventually lead to the establishment of Dinosaur National

Douglass proceeded to dig into the solid rock along those original eight
tail bones and found other parts of the skeleton. In time, the almost
complete frame of the _Apatosaurus_ was exposed. The skull was missing
and parts of the limb bones, but this was to be expected, as fossil
vertebrates are rarely preserved in their entirety. What was not
expected were the remains of a smaller dinosaur comingled with those of
its huge contemporary.


Douglass was elated. This was more than a “one strike”! How much more,
only further digging would tell. Sensing a large-scale operation, he
informed the Carnegie Museum of his prospects and readied things with
the intensity of a man at the gate of destiny. From the neighboring
ranches he recruited men, horses, and equipment. He sent for his wife
and child. He constructed a road to the discovery site, built a
five-room cabin out of logs and lumber, converted a sheepherder’s camp
wagon into an office, selected ground for future planting, bought a cow.
A forge was set up. Tools were purchased.

Back at the museum, Andrew Carnegie, himself, evinced interest. He had
always wanted something “as big as a barn” for his institution. A
special annual field fund of $5,000 was added to the regular budget to
carry on the work.

Within a year, Douglass and his men had run a cut over a hundred feet
long in the hard sandstone, digging down along the almost perpendicular
slant of the rock. At the base of this, rails were laid and small mine
carts introduced to haul away the cuttings from the rapidly developing

New specimens appeared: A small plant-eating dinosaur known as
_Dryosaurus_; an armored form called _Stegosaurus_; and another large
creature like the _Apatosaurus_. Best of all, the _Apatosaurus_ No. 1
was well on its way out of the rock and would soon be ready to ship to
the Carnegie Museum in Pittsburgh.

    [Illustration: “... I SAW EIGHT OF THE TAIL BONES OF A
    _Brontosaurus_ IN EXACT POSITION.” (FROM DOUGLASS’ DIARY, 1909.




In 1913, after 3 years of laboratory work in the Carnegie Museum the big
_Apatosaurus_ was on its feet in the Hall of Vertebrate Paleontology—1
of the 4 mounted specimens of this genus in the country and the most
perfect of all. Prepared and erected by Arthur S. Coggeshall and his
associates, it measures 71½ feet long and stands 15 feet tall at the
arch of the back.

As the excavating progressed it was not long before the diggings became
what is known to the profession as a “general quarry.” Dinosaurs of “all
kinds and sizes” were showing up. Other quarries of this type had been
developed in previous years in the Morrison formation at Como Bluff,
Wyo., and Canon City, Colo., but they contained nothing like the variety
of forms found here. Moreover, these at the monument were better
preserved and the skeletons more intact.

The remains most frequently encountered in the diggings were those of
sauropods—the huge plant-feeding dinosaurs with long tapering
extremities that lumbered about on four pillar-like legs. _Camarasaurus_
and the larger _Apatosaurus_ were typical members of this group, and
their numerous bones show them as being common animals of their time.

More common were the _Diplodoci_, of the exaggerated neck and even
longer whiplash tail. This genus distinguished itself by producing not
only the largest amount of skeletal material from the quarry, but also
the largest number of skulls—those rarest of fossils. One skull was
found in exact position with the neck bones, which settled all doubts as
to the details of this animal’s head piece. The longest _Diplodocus_ to
come from the monument extended 75½ feet.

Contrast this with the diminutive _Laosaurus_, a 2½-foot biped which
ranks as the smallest dinosaur yet taken from the deposit. This tiny
creature had hollow limb bones and was one of the agile, quick-running
types. Only one was found. When discovered, Douglass thought it a “baby”
dinosaur, but study proved it to be a full-grown specimen. The condition
of the skeleton reflected considerable agitation before and after
burial. It lay on its back, the limbs distended. The tail was gone and
the skull crushed.

In many respects, the most interesting dinosaur found was the sauropod,
_Barosaurus_. It was an extremely long-necked form, some of the
individual cervical vertebrae measuring 3 feet in length. Two specimens
were excavated.

The flesh-eaters, as might be expected from their scarcity in other
localities, made but a small showing. Two specimens of _Antrodemus_ were
unearthed. Thirty feet long, this animal was the ranking predator of its
day, although hardly comparable to the towering _Tyrannosaurus_ that
entered upon the earthly scene at a later age.

_Stegosaurus_ remains—so abundant that Douglass grew tired of them—added
a bizarre note. An armored form, it was equipped with a frill of bony
plates that extended the length of the back and terminated in a pair of
sharp spines. Its chief claim to fame rests in its supposed two sets of
“brains,” one a motor-control center situated in the hip region, and the
other in the usual place.

Everywhere they dug, the excavators found fresh material—a vast jumble
of bones so concentrated and intermingled as to make it difficult to
distinguish one specimen from another. Douglass was amazed. Obviously,
it was not with animals of a single area that he was dealing, but of an
entire region. He was dealing with a dinosaur _fauna_. He was also
perplexed. How did so many different types happen to occur in one small

Slowly, as Douglass’s acquaintance with the deposit grew, the answer
came. It was, he reasoned, the work of a river. The sandstones were
ancient sediments. In their structure and composition lay the story of
swift swirling currents. The coarse granular texture told of fast water;
the crossbedding, of shifting channels; the grouping of the bones into
clusters, of eddies.

It all added up to an old delta deposit at the mouth of a river, a
region of bars where the carcasses of dinosaurs brought down stream
accumulated. Settling, the great hulks became buried as they sank into
the receptive sand. A number of carcasses multiplied ... and slowly, as
flesh and ligament decayed, the bones became mingled, eventually to
petrify and remain preserved through the ages.

                              WORK METHODS

At the quarry, excavating continued summer and winter. The methods
employed were those that paleontologists had used for decades. There was
no compressed air, no labor-saving devices. The work was done by hand.
The crew, which seldom exceeded four men at any one time, became
veterans in the art of fossil extraction. The bone was brittle; the
encasing sandstone, hard. It required toil, patient direction, and a
knowledge of anatomy.

Judiciously placed charges of giant powder shattered the overburden.
Hand drills, wedge-and-feather, and crowbar worked the rock away, until
the bone layer was encountered. The slow attrition by hammer and chisel
accomplished the final delicate separation of the remains from the
enclosing matrix. Team-and-scraper and small handcarts removed the
rubble that swiftly accumulated in the cut. As the bones were chiseled
from the quarry face in large blocks of rock, they were encased in
strips of burlap dipped in flour paste. (Later, plaster of Paris
supplanted the flour paste.) Then they were lowered by rope onto a
mule-drawn skid and “snaked” down the trail into the gulch to await



Transporting the fossils from quarry to railhead was a major
undertaking. It required wagon trains—4-horse teams hauling high-wheeled
freight wagons over 60 miles of rutted roads to Dragon, Utah. There the
precious goods were loaded onto boxcars of the now abandoned narrow
gauge Uintah Railway, later to be transhipped to the standard gauge
Denver & Rio Grande line at Mack, Colo.

                          FURTHER DEVELOPMENT

Specimens continued to show in record abundance, most of them
duplicating the earlier finds of _Diplodocus_ and _Stegosaurus_. But
there were new forms, too. One of them was a _Camptosaurus_, the first
to be found at the quarry. It was a modified biped of plant-eating
habits, a little more than 10 feet long, with its skull and part of the
tail missing.

By 1921 the deposit had been worked to a length of 400 feet east and
west, and to a depth of about 60 feet. Rock was being stripped from the
quarry face at the rate of approximately 20,000 cubic feet annually, and
the chisels of Douglass and his men had penetrated to the richest
bone-bearing zone.

In the following year they uncovered one of the most perfect skeletons
of a dinosaur ever exhumed. It was a small sauropod named, _Camarasaurus
lentus_. When found, its 17-foot vertebral column was practically
intact, except for a few tail segments. The skull was in place, and the
limbs in their approximate positions.

It was an important find scientifically. The position of the limbs gave
clear evidence of the manner in which these animals carried themselves.
The articulation between the thigh bone and the pelvis showed
conclusively that sauropods walked with their legs more-or-less vertical
to the body and not with the bowed-out crawling posture habitual to
lizards, as many scientists had supposed. The skull was the finest known
for this genus. It was complete even to the sclerotic ring—a complex of
bony plates which surrounded the living eye and protected it.

As exhibit material it was without rival. It was mounted as found, lying
on its side, the bones fixed in death in the matrix in which they had
been preserved—a fitting climax to the 13 consecutive years that had
seen an unknown sandstone ridge in Utah become Dinosaur National

In those 13 years the Carnegie Museum had taken from the quarry parts of
300 dinosaur specimens, 2 dozen of which were mountable skeletons. Ten
different species were represented. It was the best collection of Middle
Mesozoic monsters in the world.

In the years that immediately followed, the still-rich “dig” was worked
by two other organizations—the Smithsonian Institution and the
University of Utah.

    [Illustration: _Camarasaurus_ SKELETON—THE MOST PERFECT REMOVED FROM

But finally the museums had reaped their harvest. The fruits of the
harvest had gone to enrich many of their finest displays. However, still
buried in the untouched part of the wall were the remains of still more
dinosaurs. All that was needed was to reveal them. The 67° tilt of the
rock made it a perfect exhibit face. Strip off the overlying layers,
expose the skeletons, and relief them in place. This had been Douglass’s
idea as far back as 1915, when he recorded it in his diary.

                         PROTECTING THE QUARRY

But Douglass was not the only one to realize the necessity of preserving
this unique fossil record of the dinosaurs for people of today and the
future to see on the spot. Officials of the Carnegie Museum realized the
extraordinary nature of the deposits and their contribution to our
knowledge of the past; and they were not long in taking steps to protect
the dinosaur quarry. To preserve it for science, they sought to lay
claim to it as a mineral property. But their claim was disallowed by the
U. S. Department of the Interior, because fossil bones could not be
classed as a mineral within the meaning of the mining laws.

The museum pressed its case, this time with results—but not what they
expected. The outcome was not the establishment of a mere mineral claim,
but of a national monument. Under the provisions of the Antiquities Act,
to safeguard and preserve objects and areas of significant scientific or
historic interest, the dinosaur quarry and 80 acres of surrounding land
were declared a national monument on October 4, 1915. Less than a year
later it was included in the newly created National Park System.

Several things contributed notably to this action to protect the quarry.
They were: the exceptional preservation of the bones; the number,
variety and completeness of the skeletons; the relative abundance of
skulls, consisting of 8 or more in a complete state, and about an equal
number of incomplete ones; and the finding of the first complete tails.

In 1923, knowing that the quarry was protected, and that the scientific
collection of the fossil bones for museum exhibit was at an end, Earl
Douglass turned again to the idea of making a perfected exhibit of the
fossils right where they lie. His letter to Dr. Walcott, secretary of
the Smithsonian Institution, reads, in part, “I hope that the
Government, for the benefit of science and the people, will uncover a
large area, leave the bones and skeletons in relief and house them in.
It would make one of the most astounding and instructive sights


This is precisely what the Government had in mind and, through the
agency of the National Park Service, intended to accomplish. Plans for
an in-place exhibit were drawn up. But many years were to elapse before
the plans passed from blueprint into reality.

In the meantime, the quarry entered the second phase of its existence, a
dormant period from a scientific viewpoint, but one in which the forces
of the future gathered ground.

During the 1930’s the monument served as a transient camp. A. C. Boyle
was installed as resident geologist and custodian for the Park Service.
Under his guidance a program for the general development of the area was
carried on, financed largely by WPA funds. This entailed, among other
things, the deepening and widening of the quarry cut, and the
construction of buildings later to accommodate the monument staff and

The American Museum of Natural History became interested in the
development at this time and, through its curator of fossil reptiles,
Barnum Brown, sought to initiate a joint effort with the Park Service
for exhibiting the quarry remains.

                          PRESENT DEVELOPMENT

It was not until September 1953 that the years of Park Service planning
bore fruit, and the work of developing an in-place exhibit for the
monument was begun. Many factors operated to spring the project into
being, not the least of which was the active interest and wholehearted
support of Horace M. Albright, a former Director of the Service.

Theodore E. White, formerly with the Smithsonian Institution and with
Harvard University, was placed in immediate charge, under the
supervision of Jess H. Lombard, the superintendent of the National
Monument. His task, and that of his associates, was to expose the
remaining specimens in the quarry wall and work them out in bas-relief.

A shelter had been built over the working space and power tools were
introduced for the first time. Using compressed air, the rock was scaled
off with jackhammers and “paving-breakers,” until most of the overburden
had been removed. Subsequent probing into the bone layer was done with
smaller chipping hammers, mallet, and chisel. This operation continued
through 1954 and 1955 as, slowly and carefully, the extent of the
skeletal material was determined. It comprised parts of several large
dinosaurs, sufficient in quantity to justify the next step—the
construction of a building to enclose the quarry face.

Erection of this unusual structure, the first of its design to be
attempted, commenced in 1957 and it was opened to the public in the
following year. Now, as one of the many development projects in its
MISSION 66 program, the National Park Service has resumed the delicate
work of uncovering this corner of the ancient world and preserving it
in-place for all time.

                            The Scene Today

If you stand at the overlook, you will see the Green River, Split
Mountain, and a rolling plain to the south that stretches to a hazy line
of mountains. To many, it is an unfamiliar land that lies strangely
subdued beneath a blazing sun and an intensely blue sky.

That blue sky is the key to the kinds of plants and animals that live in
this part of the monument. They live most of their lives under blue sky,
and, even when clouds do form over the mountains and drift across the
lowlands, the results are disappointing. A high wind, dust and sand, a
few drops of rain, and the storm is over.

The climatic conditions under which local plants and animals live are
conditions of extremes. On summer days the temperatures may rise above
100°, although the nights are usually cool. During the winter,
temperatures may skid to 30° below zero or more. It is not uncommon for
the thermometer to remain below zero for weeks on end. But the most
influential climatic factor is water—and there is little of it. The
total yearly precipitation is a little less than 8 inches! It is
interesting then to find such a wide variety of plants and animals that
not only survive but flourish under such rigorous conditions.

The methods used by plants in adapting to arid conditions are
interesting and varied. The wide-spreading, shallow root system and
thick stem of the cactus enhance collection and storage of water. These
strange plants are quite plump with stored water in the spring when the
snows melt, but they gradually lose this plumpness during the dry
summer, and by autumn many seem lifeless.

Other plants conserve their water by minimizing the loss through their
leaves. This may be done in a number of ways. The leaves of the spiny
greasewood are covered with a waxy substance that inhibits water loss
while the leaves of the sagebrush are covered with hairs or fuzz that
serve the same function. The leaves of the juniper are scale-like and
really don’t look like leaves at all. The most direct method of
preventing water loss through leaves is to drop the leaves themselves,
and this method is used to a greater or lesser degree by many desert
plants. The serviceberry is a good example of this method. In late
summer it looks dead, and yet the following spring finds it robed in
green and covered with flowers.

In contrast to the frugal habits of the plants just described, the
cottonwoods seem lavish indeed. Usually big trees, they spread a canopy
of green in whose shade rest birds and animals alike. Have you ever
rested under a cottonwood? If so, you will remember it as being cool
even on the hottest days. Part of the coolness was due to the hundreds
of gallons of water which are transpired through the leaves each day.
Because cottonwoods require so much water, they usually grow along
streams or near springs. Frequently they are seen along dry ravines
where their thirsty roots tap the subsurface drainage that lies hidden
below. Like the other plants however, when the supply of water becomes
inadequate they shed their leaves and wait for the next spring. Fast
growing, usually of large size, and wasteful of water where water is
dear, the cottonwood seldom lives two hundred years while the twisted
juniper on the dry, rocky ledge frequently lives as much as five

    [Illustration: SPLIT MOUNTAIN GORGE.]

Inconspicuous through most of the year are the flowering plants. Some of
these are annuals—plants that grow from seeds, mature, bloom, produce
seeds, and die in the span of a few short weeks. When the snows melt and
the sun warms the earth, the seeds that survived the winter germinate.
The usually barren hillsides produce spots of green that soon spread to
form patches as more and more plants mature. Lupine and locoweed are
purple and heliotrope splashes color along the roads, while the
fragrant, white, evening-primrose dots the sandy hillside. Scarlet gilia
and Indian paintbrush add a touch of red to the scene, and orange is
provided by the mallow.

April, May, and early June provide the best flower show as spring rains
supplement the moisture from melted snow. Their races won, their seeds
produced, the annuals wither and fade away as the temperatures rise. By
the first of July little remains of the splendid show.

Two plants do brighten the desert scene in August and September. Most
common is the rabbitbrush, a plant that grows almost everywhere. It is
rather inconspicuous except in late summer when its brilliant yellow
blossoms turn the whole shrub golden. The other is the bee plant of
which there are two species: one has yellow blossoms, and the other has
purple. These tall plants grow along washes, stream courses, roads, and
irrigation ditches. Their delicate blossoms are always surrounded by
insects drawn by the nectar the flowers produce in great quantities.

These, then, are a few of the typical plants. Each has adjusted its
needs to those limiting factors—winter cold, summer heat, and aridity. A
great number of plants grow on the monument that have not been mentioned
here, but they are like the typical plants and have similar ways of
meeting the problems of survival.

Many people who profess an interest in nature admit they cannot get very
excited about plants. Such disinterest may result in minimizing the
importance of plants in the general scheme of nature. That would be a
major error. The plants of the world are the foundation upon which other
forms of life are dependent. They alone are able to utilize the minerals
in the soil and convert carbon dioxide and water to carbohydrates.
Because of these abilities, the parade of life has been able to advance
only when the plants advance. In the present as in the past, the kinds
and abundance of plants set definite limits as to the species and
numbers of animals an area may support. Thus, if man changes the plants
of an area he will surely change the animals too, whether he realizes it
or not.

If you drive to the quarry in the heat of the day you will see only a
few of the birds that live here. They don’t like to hunt their food
during those hot hours. Frequently a turkey vulture sails majestically
above the plains along the Green River. Sometimes so high he appears to
be a speck, his telescopic eye searches the ground for the carrion upon
which he feeds. Another bird that does not mind the heat is Say’s
phoebe. He is usually found perched on a fence post, a wire, or a dead
branch waiting for some insect to buzz by. A graceful, short flight, a
pop of his beak, and then back to his perch to repeat the cycle again.
As he sits motionless, his gray breast and darker gray head and back
make him hard to see.

The time to watch birds is in the evening; as the sun sinks and the air
cools, they come forth. Small gray-brown rock wrens hop among the
boulders near the visitor center. Robins scurry through the leaves in
the stream course below the Dinosaur Quarry. Here too, western
flycatchers and Audubon’s warblers search among the cottonwoods for
insects. A flash of red and white is seen as a red-shafted flicker darts
from its nest in the hollow trunk of a tree. The sky is filled with
wheeling, twittering rough-winged swallows and white-throated swifts
that descend from their nests on the cliffs to feed upon the gnats and
other flying insects.

These are the birds that spend the spring and summer here. They raise
their families and, young and old alike, depart in autumn when frost
kills the insects upon which they feed. As they flee the cold of winter,
they are joined by many other birds that make their summer homes at
higher elevations or more northern latitudes. Ducks, geese, and swans
join the hordes moving southward. So do the various shore birds,
bluebirds, and hummingbirds.

But the sagebrush flats and brushy ravines are not left vacant by this
wholesale migration, for as the summer residents move out the winter
residents move in. The Oregon and gray-headed juncos spend the entire
winter here. Great flocks of mountain bluebirds descend from the
mountains and piñon jays make the hills resound with their screams.
Canada geese and golden-eye ducks live on the Green River and remain
until it freezes. The harsh croak of the raven is seldom heard in summer
but often in winter.

Few birds live here in winter and summer—the golden and bald eagles, the
red-tailed hawk, and the little sparrow hawk. Perhaps the most handsome
year-round resident is the magpie with its long, iridescent tail, black
and white body, and white patches on its wings. One other resident makes
his presence known by his eerie cry on frosty, moonlit nights—the
western horned owl. He hunts every night, summer and winter, but is
seldom seen. Occasionally he is disturbed upon his daylight roost and as
he skillfully dodges through the junipers, he makes a joke of the story
that owls don’t see well in daylight.

The mammals that live in the vicinity of the Dinosaur Quarry are almost
never seen. There are several reasons for this—almost all of them are
nocturnal, are very shy, and most of them are small.

In spite of their retiring habits, they reveal their presence in a
number of ways. Patches of bare earth under sagebrush and nearby sandy
slopes are crisscrossed with tiny paths beaten into the dust by deer
mice. Along the river bank, gnawed tree stumps, a few fresh chips, and
perhaps a webbed footprint tell us beaver have been active during the
night. The paired hind footprints of the kangaroo rat are common on the
hillside. Freshly fallen snow records the preceding night’s activities
in perfect detail.


Were it not for the golden-mantled ground squirrels, our evidence of
mammals would be mostly indirect. But these little fellows are very much
in evidence all day long as they play around the visitor center and in
the picnic areas. They are handsome too, with their alert black eyes,
cinnamon neck and shoulders, and dark side patches with white stripes.
Most people call these ground squirrels chipmunks because both are
striped. Actually the two are easy to tell apart; the chipmunk’s stripes
run to the tip of its nose, but those of the golden-mantled ground
squirrel extend forward only to the shoulder region. Any small, striped
mammal seen near the quarry is probably a ground squirrel, as chipmunks
are rare here.

The water problem is an ever-present one for the mammals as well as the
plants. At first this may seem strange with the Green River so close and
several springs in the hills, but most of the smaller animals have very
restricted ranges. A deer mouse, for example, seldom travels more than
100 feet from his home burrow in his entire lifetime. The kangaroo rat
and the desert woodrat also have limited ranges although theirs are
somewhat larger than those of deer mice. The majority of such animals
must meet their water needs without springs and seeps. How do they do



The food they eat contains some water. The green vegetation of
springtime contains large amounts. Even air-dried foods such as seeds
contain some. And these animals don’t need much. Through the thousands
of years these little creatures have lived in arid lands, evolutionary
processes have altered their bodies and life patterns to fit the
conditions under which they must live. Surely one of the most useful and
interesting of their abilities is that of utilizing metabolic water.
Such water is obtained through oxidation of hydrogen contained in food
and is a by-product of metabolism. Putting it another way, during the
digestive process these animals are able to manufacture water from the
chemical constituents of their food and the oxygen in their blood. The
amount of water thus obtained is between 70 and 100 percent of the dry
weight of the food eaten. Thus some desert animals are able to live a
normal life span without ever taking a drink, and probably many of them

Carnivores such as the badger and the coyote get some of their water
from the animals they eat and may go for days without visiting a spring.
But eventually they return to the river or a spring for a drink. This is
no special effort as carnivores generally range for miles in search of

Winter is a time of difficulty for most animals. Some of them like the
ground squirrels hibernate and sleep the winter away, but the majority
must rustle their “daily bread.” Winter storms drive the mule deer down
from the high country. Mice tunnel through the snow in search of food.
The white-tailed jackrabbit and the snowshoe hare change their coats
from brown to white. In particularly hard winters the animals die in
great numbers, first the weak and old, then the young, and sometimes
even animals in prime condition fail to survive.

The reptiles that make their homes in the Quarry Area of Dinosaur
National Monument are few in number. The rattlesnake is rare and seldom
seen. The only common snake is the bull or gopher snake. This snake can
appear very threatening as it swells its body and hisses loudly, but it
is not poisonous. Gopher snakes climb well and are often seen in trees
where they hunt for eggs and young birds.

Two lizards are commonly seen here during the summer. The side-blotched
lizard is about 1¾ to 2⅛ inches long with a somewhat longer tail. These
small brown lizards are frequently seen among the rocks near the parking
and picnic areas. The name, side-blotched lizard, is taken from the
black or bluish-black area behind the foreleg of the males. These
lizards are also called brown utas.

The western whiptail is also a very common lizard. As its name suggests,
it has a very long slender tail which it lashes from side to side as it
runs. This lizard is easily distinguished from the side-blotched lizard
by its larger size, longer more slender tail, and the presence of bars
and spots of black upon its back. In late summer, junior-sized young
whiptails appear, but their 3-inch total length is unimpressive compared
to 8-inch adults. The young are quite handsome with pleasing body colors
and bright-blue tails.

Often lizards are seen whose tails are missing. When the tail is pulled
or injured it can be shed by its owner. The shed tail may wriggle for
several minutes and attract the predator’s attention while the lizard
escapes. The tailless lizard soon grows another one that is usually
recognizable by its subdued or otherwise different color pattern.
Sometimes the broken tail does not fall off so it and the new tail form
a fork.

In summary then, we see that this apparently lifeless desert does
support a wide variety of living things and a great number of
individuals. Some of them, the plants and small animals, live here all
year round while others, such as most birds, live here only part of the
time. But whatever the length of stay, all living things must adapt
themselves to existing conditions at the time of their stay. If they
cannot adapt to static or changing conditions they must move or become

Some 60 million years have passed since the dinosaurs ruled the world.
In that time mountains have risen, wasted away, and risen again.
Glaciers have come and gone. Many species of plants and animals evolved
and passed on to extinction. Every life form meets the test—adapt or
die. That test is as real to the dusty lizard basking on the quarry face
as it was to the dinosaurs whose bones you came to see.

                          Key to Pronunciation

  Dinosauria            (dy-noh-SAWR-eea)
  Antrodemus            (an-troh-DEE-mus)
  Apatosaurus           (apato-SAWR-us)
  Ankylosaurus          (an-KEELOH-sawr-us)
  Camptosaurus          (camp-toh-SAWR-us)
  Stegosaurus           (steg-oh-SAWR-us)
  Triceratops           (try-SER-a-tops)
  Archosauria           (Ark-oh-SAWR-eea)
  Mesozoic              (MEZ-oh-zoh-ic)
  Triassic              (try-ASS-ic)
  Jurassic              (jur-ASS-ic)
  Cretaceous            (kre-TAY-shus)
  Tyrannosaurus	        (ty-ran-oh-SARH-us)
  Saurischia            (sawr-ISS-key-a)
  Ornithischia	         (orni-THISS-key-a)
  Diplodocus            (di-PLOD-icus)
  Camarasaurus	         (camara-SAWR-us)
  Protiguanodon	        (pro-teeg-GUAN-oh-don)

                           Suggested Readings

  Andrews, Roy Chapman. _All About Dinosaurs_, 146 pp. Random House, New
          York. A very interesting book about dinosaurs and the men who
          study them. Children, 9-12 years old.
  Colbert, Edward H. _Evolution of the Vertebrates_, 479 pp. John Wiley
          and Sons, Inc., New York. 1955. A very readable account of
          vertebrate evolution for the student or serious amateur.
  —— ——. _Dinosaurs_, 4th ed., 32 pp. American Museum of Natural
          History, New York. 1957. A good brief treatment of all
          dinosaurs. Excellent illustrations.
  Dunbar, Carl O. _Historical Geology_, 567 pp. Wiley, New York. 1949.
          An excellent treatment of earth’s history and life from the
          beginning to the present.
  Life Editorial Staff. _The World We Live In_, 304 pp. Simon &
          Schuster, New York. 1955. Elaborately illustrated book about
          the world’s natural history.

                          Transcriber’s Notes

—Retained publication information from the printed edition: this eBook
  is public-domain in the country of publication.

—In the text versions only, text in italics is delimited by

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