Dinosaurs

Large reptiles that lived on Earth millions of years ago and are now extinct.

The word "dinosaur" was created in 1842 by Sir Richard Owen, a scientist working at the British Museum, now known at the British Museum of Natural History. His original word was "dinosauria" which means "fearfully great lizard," from the Greek, deinos — "fearfully great" and sauros — "lizard." He created this word after some giant fossils of reptile-like creatures were discovered in England earlier in that century. Since that time, "dinosaur" has become a common word all over the world for a group of creatures with strange names and unknown histories.

What we commonly think of as dinosaurs lived from about 230 million to about 65 million years ago, and they ruled the earth for over 140 million years! Check out this "geologic staircase of time" to learn about how old the earth is, and when the dinosaurs lived! Some creatures that lived during the time of the dinosaurs, such as the alligator and shark, still live today.

Although there has been a lot learned about dinosaurs, scientists are still discovering details to help them determine what dinosaurs looked like, how they lived, and what the earth was like during the time they lived. Scientists who study ancient life are called Paleontologists.

The dinosaurs lived on the earth during what is called the Mesozoic period. This time is divided into three periods: the Triassic (251-199.6 million years ago), the Jurassic (199.6-145.5 million years ago), and the Cretaceous (145.5-65.5 million years ago).* Find out more about these time periods at this University of California Museum of Paleontology site.

* Dates are from the International Commission on Stratigraphy's International ChronoStratigraphic Chart.

Not even close!!! The dinosaurs were long gone, or extinct, before people appeared in Earth's history. 65 million years passed away before humans were around. Cartoons and movies make a great story out of cavemen fighting off huge dinosaurs, but it never could really have happened.

There are several theories as to what happened to the dinosaurs, but scientists don't know for sure. Here are some of the current theories about why the dinosaurs died:

• An asteroid hit the earth causing climate changes.
• Massive volcanoes erupting all over the earth caused acid rain and global climate changes.
• A supernova star caused them to die from radiation.
• Continental drift altered the climate.
• They died from disease.

Learn more about dinosaurs and how they may have died at this Classroom of the Future site.

For many years, scientists did not know whether dinosaurs had ever lived in Idaho because no dinosaur fossils had been found. But in 2014, paleontologists made an exciting discovery in Eastern Idaho: Cretaceous Era fossils from three types of theropods, the family of carnivorous dinosaurs which include Tyrannosaurus Rex, and the fossilized eggs of a large oviraptorosaur!

Besides dinosaurs, there have been a large number of other ancient fossils that have been found in Idaho. The most famous is the Hagerman Horse, one of the earliest known ancestors of the modern-day horse! The Hagerman horse was a species known as the Equus simplicidens and lived during the Pliocene period. It may have been related to the zebra.

The Hagerman Horse National Monument is located about 100 miles southeast of Boise and has one of the largest concentrations of horse fossils in North America!! Besides horses, there have been over 140 animal species and 35 plant species identified from the Pliocene age at the Hagerman Horse National Monument.

Dinosaur fossils have been found in Idaho and in many surrounding states. Dinosaurs have been found in Montana, Utah, Colorado, Wyoming, and Canada! Dinosaur fossils have been found on all seven continents around the world.

A fossil is a kind of mold of a plant or animal whose remains sank to the bottom of a lake or other body of water after it died. Sediments covered over the plant or animal, creating layers and layers that protect the body from fast decay. After much time had passed, these layers of sediment became hard. The layers of sediment eventually turned to rock with the impressions of a plant or animal embedded in its layers.

Fossils can also be found in hardened tree sap, called amber; in volcanic ash; tar pits; bogs; and quicksand. Footprints can also be fossilized.

Dinosaurs can be grouped into two main categories:

Saurischia, or "lizard-hipped"

The lizard-hipped dinosaur group contains herbivores and carnivores. In this category, there are 2 major groups of dinosaurs:

• Sauropoda — this group contains herbivore dinosaurs like Diplodocus and Apatosaurus.
• Theropoda — this group contains the fearsome carnivores like Allosaurus, Deinonychus, and the "King of Beasts," Tyrannosaurus Rex.

Find out more about Saurischia dinosaurs here.

Ornithischia, or "bird-hipped"

The bird-hipped dinosaurs were all herbivores (plant-eaters). In the Ornithischia category, there are 3 major groups of dinosaurs:

• Thyreophora — this group contains armored dinosaurs like Stegosaurus and Ankylosaurus.
• Marginocephalia — this group contained the horned dinosaurs like Protoceratops and Triceratops.
• Ornithopoda — this group contained duck-billed dinosaurs like Hadrosaurs and "different toothed dinosaurs" like the Heterodontosaurus.

Learn more about the Ornithischia dinosaurs by clicking here.

For information on how dinosaurs get named, visit The University of California Museum of Paleontology.

The first known dinosaur fossils were found in the 1820's in England. Since then dinosaurs have been discovered on all seven continents! So how do paleontologists find their fossils? When scientists go looking for fossils, they investigate areas where the sedimentary rock is between 65 and 230 million years old. But, sometimes paleontologists find dinosaurs by accident. As the earth is exposed to weather, the ground and rock erodes, exposing the fossils. Dinosaur fossils have been found by farmers, miners, road workers, and even kids! So as you are exploring, keep your eyes open!

A great fossil site in Idaho is Tolo Lake, which is located near Grangeville. In 1994, construction crews made a surprise discovery when they unearthed a huge bone! This surprise led to the discovery of several mammoths and ancient bison.

• Largest — The largest dinosaur ever found may have been the Argentinosaurus, first discovered by a farmer in 1988. The Blue Whale is still larger.
• Smallest — The microraptor may have been the smallest dinosaur at 16 inches tall. This dinosaur was discovered in China in the year 2000. It was a bird-like creature with feathers, but may not have been capable of flight. It even had wings on its back legs.
• Fastest — It would be hard to judge the fastest dinosaur since no one was around then to compare them. But the Ornithomimus may have been able to keep up with a present-day ostrich which can run up to 43 mph.
• Oldest — The oldest known dinosaurs were from the Triassic period. The prosauropods from Madagascar are the oldest, about 230 million years old.
• Biggest egg collection — Over 100 dinosaur eggs were discovered in India all in one location thought to be a nest. Large footprints were discovered nearby.

• 8 inches — The length of a T. Rex tooth, the largest tooth of any meat eater.
• 500 pounds — The amount of meat a T. Rex could swallow in one bite.
• 6 feet long — The length of the skull of the biggest meat-eater ever, Giganotosaurus.
• 930 — The number of kinds of dinosaurs.
• 21 days — The current average time between dinosaur discoveries — the fastest pace ever.
• 5 feet high, 4 feet wide — The largest bone in the world? A backbone of Argentinosaurus, a plant-eating dinosaur and the largest animal ever.
• 120 tons — The weight of 1 Argentinosaurus, the heaviest of all animals, equal to 100 elephants.
• 33 feet — The longest neck of any animal? Mamenchisaurus, a planteater 68 feet long.
• 228 million — The age of the oldest dinosaur, the dog-sized meat eater Eoraptor from Argentina.