When did dinosaurs live?

Dinosaurs and other extinct creatures are not around anymore, but we know they lived a long time ago.  "When" is the question!  No one is quite for sure.  Scientists are going back and forth saying thousands to millions to millions to thousands years ago.  The truth is every year it changes.

What are Dinosaurs?

A long time ago, a new group of reptiles appeared on Earth.  Like all reptiles, they had waterproof, scaly skin and young that hatched from eggs.  These creatures also were like birds. Some had feathers, and some did not.  These were the dinosaurs that lived on Earth for a long time and then went extinct.

Dinosaurs are divided into two groups based on the shape of their hips:  Ornithischians (bird-hipped) and Saurischians (lizard-hipped). Ornithischians had their two lower hipbones pointing downward and backward.  Saurischians had one lower hipbone pointing downward and forward, and the other downward and backward.  

Tyranosaurus Rex

(Lizard-hipped)

Iguanodon

(Bird-hipped)

Skin

When dinosaurs die in mud, they can leave trace fossils of their skin behind.  Scientists have found feathers, fossilized shell, and mummified skin.

The Ornithischians

Gastonia (gas-TONE-ee-ah)

Gastonia was one of the most heavily armored of all dinosaurs.  A jumble of more than a thousand of gastonia's bones and bits of armor were discovered together.   

Found in Utah

Pachycephalosaurus (pack-ee-SEF-ah-low-SORE-us)

Although its fossils are rare and no complete skeleton has been found, paleontologists have found enough evidence to show that Pachycephalosaurus was a strong, two-legged dinosaur.  It had a thick, bony dome on its skull, which it used as a weapon in its clashes with rivals over mates or territory.  Pachycephalosaurus could ram heads together due to the large dome on their head.

Found in South Dakota, Montana, and Wyoming

Triceratops (tri-SERR-uh-tops)

Triceratops was one of the largest of the horned dinosaurs.  It may have been one of the most common dinosaurs in the North American West at the time of Tyrannosaurus.  These dinosaurs are often pictured traveling in large groups, but the biggest gathering of Triceratops ever found consisted of three youngsters.

Found in Western Canada & Western US

Muttaburrasaurus   (mutt-ah-BUHR-ah-SORE-us)

Muttaburrasaurus had very strong jaws.  Its teeth were designed to slice through plants.  It had a large lumped nose that was probably used to make a high-pitch scream or a loud muttering sound to communicate.

Found in Australia

The Saurischians

Coelophysis  (SEE-low-FIE-sis)

Coelophysis was a light little meat-eater and probably a fast hunter.  On January 22, 1998, a Coelophysis skull was taken on a space shuttle.  

Found in Arizona & New Mexico

Spinosaurus  (SPINE-oh-SORE-us)

Spinosaurus was the longest and largest of the meat-eating dinosaurs.  It may have grown to 50 ft long.  Spinosaurus was a good swimmer.  No one is certain what the Spinosaurus looked like because the greatest skeleton was destroyed in World War II.

Found in Egypt, Morocco, Libya, Tunisia, Algeria