Dinosaurs have always fascinated me.
I thrilled to "One Million B.C." with Raquel Welch
and the great animated dinosaurs. To be completely accurate,
dinosaurs have been extinct for 66 million years, so
the movie's title is off by a few million years. Of
course, everyone knows people didn't live during those
days either, but I liked the movie in spite of its errors.
Interest in the dinosaurs is bigger today than ever.
Just look at the success of such movies as "Jurassic
Park." More new findings and species are being dug up
now than ever before. I guess the popularity of dinosaurs
is due to the fact that these kind of amazing creatures
actually existed. Over the years, theories have changed,
discoveries have been made, and science has given the
dinosaurs a makeover. Once thought to be cold blooded,
sluggish reptiles, the image of dinosaurs today is one
of vital, hot-blooded beasts, much more dramatic than
the plodding behemoths of my youth. Somehow, in my mind,
I must have always known this to be true. How could
these creatures have captured my imagination so completely?
How could they have dominated the earth while other
animal forms hid in the shadows? Rather than being the
evolutionary failure most people stereotype them as,
they are, on the contrary, one of the most successful
forms of life to have come along. Their kind ruled the
earth for 155 million years, while people have been
around for perhaps 4 million (modern humans even less).
Descendents of the dinosaurs live among us today in
the form of birds.
Here is some basic information about what we know about
AGE OF REPTILES
Dinosaurs lived in a block
of time called the Mesozoic Era, which began
about 248 million years ago an lasted 182 million years.
The Mesozoic era is divided into three smaller blocks
of time called Periods.
The earliest period was the Triassic, which lasted
from 248 million years ago to 208 million years ago.
This period saw the beginning of the dinosaurs (towards
the end of the period), and was actually dominated by
other animal forms that, at the time, were larger and
more numerous than the primitive dinosaur forms.
Next came the Jurassic Period, which lasted until
144 million years ago. This was the age when dinosaurs
really took over, with animal forms reaching immense
size and incredible shapes. The first bird forms are
believed by most paleontologists to have evolved in
The last age of dinosaurs was the Cretaceous Period,
which started 144 million years ago and lasted to
66 million years ago. Some of the most familiar dinosaurs
forms evolved and lived during this time, including
the ceratopians (Triceratops), and hadrosaurs
(duck-billed dinosaurs). Probably the most famous
dinosaur of all, Tyrannosaurus Rex, lived during
At the end of the Cretaceous period, all fossil evidence
of the dinosaurs disappears. Throughout Earth's history
species have vanished during happenings called mass
extinction events. All through the history of the
earth, including the Mesozoic Era, and Cenozoic
Era (the age of mammals, which includes the present
day), mass extinctions have wiped out many forms of
life, which were then replaced by other forms. The mass
extinction event at the end of the Cretaceous wiped
out many forms of life, including the dinosaurs, pterosaurs,
and the huge marine reptiles. What caused these extinctions
is still in dispute, and may never be truly solved.
The most recent popular theory is that the extinctions
were triggered by a large asteroid or comet smashing
into the earth's crust.
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WHAT ARE DINOSAURS?
Dinosaurs were a group of animals,
now extinct, which lived during the Mesozoic Era. Some
were quite small, chicken or dog sized, while others
reached incredible size, becoming the largest land animals
to exist on the earth. Although they are called reptiles,
most scientists today believe that at least some dinosaurs
were warm-blooded. Fossil evidence indicates that they
laid eggs, and some may have fed their young by bringing
food to their nests, as birds do today. They ruled the
earth for about 155 million years, finally dying out
66 million years ago during a mass extinction at the
end of the Cretaceous Period.
came in two forms or groups. One group is called saurischia(reptile-hipped),
which includes the theropods (all carnivorous
dinosaurs were theropods), and the sauropods
(the largest of all land animals were sauropods). The
other group is known as ornithischia (bird-hipped),
and all species in this group were herbivores.
The ornithicians can be further divided into five sub-groups,
the ankylosaurs (armored dinosaurs), ceratopians
(with parrot-like beaks, most had bony shields and horns),
ornithopods (which include Iguanodon and the
duck-billed dinosaurs), pachycephalosaurs (similar
to the ornithopods, but with bony, domed heads), and
the stegosaurs (another armored group, with bony
back plates and spiked tails). Interestingly, birds
seem to have developed from the reptile-hipped group
(specifically, the theropods).
All dinosaurs lived exclusively on the land, no specimen
has been found that could fly or swim in the ocean.
Many animals that lived in and around the time of the
dinosaurs have been mistaken by people as being dinosaurs.
Here are some of the most popular examples:
Dimetrodon was a dinosaur-like creature that lived in
the Permian Period at the end of the Paleozoic Era.
A flesh eater, it was more closely related to mammals
than to dinosaurs, which didn't evolve until millions
of years later.
Pterosaurs were a group of reptiles that developed a
thin membrane of skin that stretched from elongated
fingers to its back legs, allowing them to fly. Evolving
from a group of early archosaurs during the Triassic
Period, they existed for longer than the dinosaurs,
finally dying out in the mass extinction event at the
end of the Cretaceous along with the dinosaurs. Birds
did not evolve from pterosaurs, as some may believe.
The marine reptiles were a varied group that lived in
much the same ways as whales and dolphins do today.
Ichthyosaurs, plesiosaurs and mosasaurs
ruled the seas and oceans as the dinosaurs did the land.
The ichthyosaurs in particular were incredibly dolphin-like,
even giving birth to live young while swimming in the
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