|Dinosaurs lived only during the Mesozoic, which spans a period of time
from about 245 million years to 65 million years ago. The Mesozoic Era
is commonly called the Age of Dinosaurs, although dinosaurs did not originate
until near the end of the Triassic. The Mesozoic is divided into three
time periods: the Triassic, Jurassic, and Cretaceous.
|Dinosaurs first appear at the end of the Middle Triassic or in early
Late Triassic time, approximately 230 million years ago. The primitive
dinosaurs of the Triassic were neither as abundant nor as varied as they
would become in Jurassic and Cretaceous times. The dinosaurs are a large
group of reptiles belonging to the Archosauria ("ruling reptiles"), which
also includes the pterosaurs, or "winged lizards"; crocodilians, the only
surviving archosaurs; and the thecodonts, primitive "socket tooth" archosaurs,
who were the ancestors of all other archosaurs. Dinosaurs are classified
into two major orders, the Saurischia ("lizard-hipped") and the Ornithischia
("bird-hipped"). The saurischians include of the herbivorous Sauropodomorpha
(sauropods and prosauropods) and the carnivorous, bipedal Theropoda. The
ornithischians are a more varied group of herbivores, including the stegosaurs,
ornithopods, ankylosaurs, and ceratopsians. Modern birds are descended
from the theropod dinosaurs.
|These major groups were just developing in Late Triassic time. The
Herrerasauria, a Triassic group of primitive bipedal predators, may be
ancestral to all dinosaurs, because they had characteristics too primitive
to be classified as either saurischian or ornithischian. The saurischian
dinosaurs of the Triassic are represented by the Coelophysids, a small
and primitive family of the theropods, and by the Prosauropods, smaller
ancestors to the quadrupedal sauropods. The ornithischian dinosaurs are
represented by the unclassified Fabrosaurs and a family of very primitive
ornithopod known as Heterodontosaurids. Recent discoveries in South America
are refining our knowledge of the earliest dinosaurs.
Dinosaurs have reached a new level of interest and controversy with
the purchase of the 65-million-year-old Tyrannosaurus rex, as called T-rex,
for $8,362,500 by Chicago’s Field Museum of Natural History. This T-rex
discovered it in South Dakota on a Cheyenne River Reservation. This was
the most complete T-rex ever discovered, being 90 percent complete, and
with over 400 bones. The selling price demonstrates that people find a
great interest in dinosaurs, but it also demonstrates that dinosaurs have
passed a point of science, and entered the realm of business. How will
science suffer from this?
|Unfortunately for us, none of us here have discovered any dinosaur
bones, or any of their wonderful reminders. What reminders are those you
say? Well, coprolites of course, also known by the more technical term
of dino dung! Yes, this creatures left their calling cards in life, but
they do not stick to your shoes, or get you that unwanted attention when
you walk into the room after accidentally finding some. Coprolites are
more abundant of the fossils found of dinosaurs and they can provide information
about what a dinosaur liked dine on. For those more interested in this
subject, and for those who want to know about obtaining such wonderful
keepsakes, should click on the image of a coprolite below.
|Other reminders that dinosaurs left behind besides fossils are dinosaur
tracks. In Texas, there are sixteen known sites, with the most popular
being near Glen Rose, at Dinosaur Valley State Park. To learn more about
this location, and other dinosaur track sites, just click on the icon below.
|For those interested in reading more about dinosaurs, there are many
good authors to chose from, and many good books to read. Our personal favorite
author is Louis L. Jacobs, Ph.D., who has published some wonderful books
to read, including Lone Star Dinosaurs and Quest for the African Dinosaurs.
To learn more about this author, and his books, click on the icon below
If you want to visit a dinosaur site that is both interesting,
and a little different, then click on the icon below.
AN INTERESTING SITE
|We want to make sure that you find what you are looking for, so we
have added an extra place for you to visit, and it can take you to even
more places and resources. Just click on the icon below.
To learn more about other fossils, and to see some examples of
what we have found, be sure to visit our other pages on fossils. To do
this, just click on the icon below to return to the Paleontology room,
and click on the other fossil images.