Dinosaur Facts

Dinosaurs ['dī-nə-sȯrz]

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

What is a Dinosaur?

brachiosaurus in water
brachiosaurs in water

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.

Historic Periods of Time

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.

geologic time spiral

Did People Live With Dinosaurs?

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.

Geochronological scale

Where Did The Dinosaurs Go?

triceratops fossil skeleton
triceratops skeleton

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:

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

Did Dinosaurs Live in Idaho?

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.

Hagerman horse
Hagerman horse

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.

Where Did Dinosaurs Live?

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.

United States map of dinosaur fossil locations
United States map of dinosaur fossil locations

What is a Fossil Anyway?

Trilobite fossil
Trilobite fossil

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.

Kinds of Dinosaurs

Dinosaurs can be grouped into two main categories:

Diplodocus dinosaurs herd
Diplodocus dinosaurs herd

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.

Dinosaur Fossils

fossil excavation exhibit

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.

Fun Facts

  • 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.

By The Numbers

  • 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.

Top 10 Questions

November 2012

Thanks to David Varricchio, Assistant Professor of Paleontology, Earth Science Department, Montana State University for the answers.

  1. How did the dinosaurs go extinct?

    We know some things that occurred about the time dinosaurs went extinct. There were major changes in climate due to a lot of volcanic eruptions that altered the earth's atmosphere and changed temperatures. Also, there is really good evidence that an asteroid hit the earth's surface. These probably contributed to the extinction of dinosaurs. However, if you ask ten different paleontologists why, they will have ten different reasons. (From Cagney at Shadow Hills Elementary School in Boise)

  2. How did dinosaurs become fossils?

    Bones have a mineral crystal component to them. In some ways, they are like rocks to begin with. Other parts of our bones are filled with blood and nerve tissue. That material gets eaten by bacteria and rots away, leaving spaces. Through time, water under ground percolates through the rock and deposits other minerals and crystals that grow inside the spaces in that bone. (From Devon at Maranatha Christian School in Boise)

  3. How long did dinosaurs live?

    Dinosaur bones record growth lines, like the trees have growth rings. You can look at trees and count how old the tree is. In the same way, you can look at dinosaur bones and get an estimate of their age by looking at the growth lines. For the big dinosaurs, they lived 10, 20, maybe even 50 years. (From John at St. Mary's School in Moscow)

  4. Are dinosaurs related to birds or reptiles?

    You can think of dinosaurs and birds as really belonging to the reptile group. We typically think of them, as well as turtles, lizards, snakes, and crocodiles, as belonging to that group. We can say that birds are dinosaurs, and that dinosaurs and birds are reptiles. (From Ben at Clearwater Elementary School in Kooskia)

  5. How many species of dinosaurs are there?

    We can only guess at how many there were. When we look at the rocks that dinosaurs are found in, we probably only see a small sample of all the dinosaurs that once lived. So far, scientists have named about 600 species, but it's estimated that there may have been 2,000 or 3,000 dinosaurs through the whole Mesozoic Era. (From Dani at Lena Elementary School in Moscow)

  6. Why does a small mammal survive, but not the dinosaurs?

    Some people think that the small animal may have been able to find shelter, such as crawling into a burrow, when the asteroid hit. Other small animals, like turtles and frogs, may have swum down to the bottom of the pond and hidden in the mud for a few months. Big animals require lots of food and space, whereas smaller animals can get by on very little. (From Nicole at Pine Forrest Elementary School in North Carolina)

  7. In what era and what kind of dinosaurs lived in Idaho?

    We have rocks in eastern Idaho that are from 100 million years ago. That's the Cretaceous period. One dinosaur that has been found is the oryctodromeus. It was about the size of your typical dog, not a very big dinosaur. It ate plants. We've found teeth from some carnivorous dinosaurs, maybe raptors. There may be a big ductile type animal as well. Also, even though we have no bones, we do have eggs from what may be a big giant oviraptor. (From Parker at Highlands Elementary School in Boise)

  8. How many bones are there in a velociraptor?

    Velociraptors had a lot of bones, probably in the neighborhood of about 250. (From Jack at McDonald Elementary School in Moscow)

  9. Which dinosaurs had feathers?

    It's only been a few years since we've found feathers on dinosaurs. So far, the most common are the meat-eating dinosaurs, particularly the smaller ones. They are closely related to birds. Recently, feathers have been found from tyrannosaurus relatives. (From Ben at Horizon Elementary School in Boise)

  10. How many teeth did they have?

    They had about 60 teeth in their jaws at one time. For each tooth that you could see, they had a tooth that was ready to replace it. So in their smile, you would see about 60 teeth, although there were probably about 120 teeth total, half that you wouldn't have been able to see. (From Kendall at Camelot Elementary School in Lewiston)