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Ancient
Southwest Dinosaurs
Far, far back in ancient times, long before human beings are known to
have walked the earth, the world was very different from what we see today.
The continents we now see on our world maps were once all connected in
a single land mass that scientists have named Pangaea. Not only was the
shape of our land mass different, so were the plants and creatures who
lived there.
245 million years ago, the Mesozoic Era began,
and it lasted until 65 million years ago.
During this time, the continents began as one mass, and slowly broke up,
shifting positions, disrupting animal populations, and changing climates.
During the Mesozoic Era, scientists have divided the time period into
three sections : Triassic (245-190 million years ago), Jurassic (190-140
million years ago), and Cretaceous (140-65 million years ago). This period
was the middle (meso) period of Earth's animal life (zoic) development,
preceded by insects, amphibians and reptiles, and followed by mammals.
300 types of dinosaurs have been found in the world to date, and 80 of
those have examples found in North America. There are also types that
have been found in areas no longer connected - like North America and
Africa ! At least 25 of the 80 North American dinosaurs have also been
found in the southwest.
Climate changes and changes in the geography of North America caused the
Ancient Southwest to often look very different than it does today. At
first, during the Triassic, when Pangaea was one land mass, the climate
was warm, tropical and moist. Giant ferns and horsetail covered swamps
and low lands. As time went on, mountains rose, and our first pine forests,
giant sequoias, and cycad forests began to grow. By the Jurassic period,
the continents had begun to shift and North American became part of Laurasia,
joined to Europe and Asia. During this time parts of the Southwest were
deserts, and the west coast of North America was still a low land covered
by the Pacific Ocean. At times large sections of the northern Southwest
were also under sea water as the ocean extended down from the Arctic into
Utah.
By the Cretaceous, Laurasia had completed separated from Africa and South
America, and North America slowly moved off to become its own continent,
eventually joining with South America. Again things grew warm and moist,
and tropical dinosaur birds came to fly across the earth as the dinosaurs
walked below. The first flowering plants appeared. The Southwest was covered
by grassless tropical jungles and swamps, creating coal deposits hundreds
of feet thick as the plants settled into the swamps and decayed. Oaks,
poplars, walnut, ash, laurel, willows, palms, cypress, eucalyptus, persimmon,
magnolia, honeysuckle and dogwood we know today flourished in the Cretaceous.
Baja California was thickly wooded and covered with dense vegetation.
Then in the middle of the Cretaceous, things began to cool off, and overall
became drier. Even around the equator the dense tropical forest became
more open, less forested savannahs. It seems that eventually there was
not enough plant food to support the huge population of dinosaurs, due
to climatic and catastrophic changes. 65 million years ago, the Age of
the Dinosaurs came to an end, only their bird descendents living on.
Did you know that dinosaurs are not really extinct ? They actually live
on today as birds. For a long time scientists thought the hollow bones
of birds related them to the types of dinosaurs that had hollow bones.
And when they found fossils of large reptile-skinned flying dinosaurs
they were more certain of this link. But in very recent years, three dinosaur
fossils have been found in China that show evidence of having real feathers,
making the suspected link an accepted fact today.
Do you think all dinosaurs were huge lumbering monsters with vicious teeth
eating anyone in their way ? You might be surprised to know that in the
Ancient Southwest, there were dinosaurs the size of large rabbits,
that the majority of those found were peaceful
plant eaters, and that one of the largest finds is not really even a dinosaur.
Also, those big terrifying creatures like the Tyranosaurus Rex might not
have been a hunter, he might have been a scavenger. In fact, there is
a lot we do not - and may not ever know - for sure about the dinosaurs,
so as we study them, understand that our dinosaur knowledge has only been
developed in the last 150 years, that every year new discoveries are being
made, and that we now think we know may easily be changed as new evidence
is uncovered. That is the excitement of studying dinosaurs ! One thing
we do know is that there were two main types of dinosaurs, and it is the
shape of their hip bones that distinguishes them. One is called a lizard-hipped
dinosaur (saurischain ) and the other is called a bird-hipped dinosaur
(orinthiscian). This distinction has to do with the angle of the their
hip bone, and divides all dinosaurs into two main groups. In each group,
some were small and fast, others were huge and lumbering. Some ate plants,
others hunted, and still others may have scavenged. Scientists study their
fossils to learn where they lived, what they ate, how fast they walked,
if their sight or smell was their best asset, how their muscles worked,
and from those insights, draw conclusions about the dinosaurs life.
What is a fossil ? What we know about dinosaurs we learn from the fossil
record. What is a fossil ? The word actually means 'something dug up'.
You may think it means bones and teeth, but there are many other kinds
of fossils as well. What all fossils have in common is that they have
been preserved for thousands or millions of years because they were quickly
buried by sand and silt, keeping them protected from the sun and air above.
While buried, the fossils are often slowly filled with water, and minerals
in the water permeate the original object. This might mean a bone, a dinosaur
track, a dinosaur egg, a seashell, a fern frond, or even an entire fallen
tree. Over millions of years, these objects harden and dry, and when we
discover them today, they are the same shape they were when they fell,
telling us a lot about what life was like in their time. The Petrified
Forest of Arizona is an example of fossilized trees, much like the dinosaur
finds are fossilized bones and traces of the dinosaurs that have been
preserved over millions of years. And sea shells have been found as far
inland as Utah, and in the foothills of the Sierras and Cascades, telling
us the seas were once covering areas of the earth we might never have
imagined. All this news comes courtesy of the Fossil Record !
Who finds dinosaurs ? Since 1600 BC, people around the world have recorded
finding massive bones and huge teeth in rock and soil formations. By the
1840s, Paleontology was becoming a recognized field of scientific study,
and in 1842, the name dinosaur was selected to describe these "Fearfully
Great Lizards'. In the 1870's a fierce and bitter competition between
two American paleontologists, Mr. Edward Drinker Cope and Professor Othniel
Marsh, brought the dinosaur discovery process into the public light as
they wrangled to out do one another in collecting specimens in Colorado,
Wyoming, and Nebraska. By the 1880s dinosaur fossils were being discovered
in New Mexico, and now dinosaur discoveries have been made in Utah, Colorado,
Arizona, New Mexico, Texas California and Baja California, spanning the
full Southwest. But not all dinosaurs - or fossils - are discovered by
scientists. Some have been discovered by school teachers, parents and
children, hikers, while others are unfortunately stolen in mass quantity
by thieves who illegally take and resell their finds. Other dinosaur discoverers
who are scientists are not the Paleontologists who study physical dinosaur
bones - they are Ichnologists. Ichnologists study the traces of dinosaurs
- their foot prints, eggs, dung, even skin imprints in fossils. Together
the public and scientists are learning more about these amazing creatures
every day … let's explore some more.
Dinosaur Time Line
Triassic Gallery
Jurassic Gallery
Cretaceous Gallery
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