There are two major groups of dinosaurs that can be divided into the more famous seven groups of dinosaurs. Saurischia ("lizard-hipped", not really lizard-like but close enough)
* Theropods (two-legged meat-eaters, and birds)
* Sauropodomorphs (Two and four-legged plant-eaters with long necks)
Ornithischia ("bird-hipped", not really bird-like but close enough)
* Ornithopods (two-legged plant-eaters)
* Stegosaurs (plated dinosaurs)
* Ankylosaurs (armored dinosaurs)
* Pachycephalosaurs (dome-headed dinosaurs)
* Ceratopsians (horned dinosaurs)
The word dinosaur comes from the ancient Greek words deinos ("fearfully great", as in awe-inspiring) and sauros (a lizard). The name was invented in 1842 by Richard Owen, who knew they were not lizards, but thought that they may have been derived from them. Owen used the term deinos as a superlative. It was sometimes interpreted as "terrible" in the sense of "inspiring terror". Unfortunately, in more recent decades, this word has come to mean "bad" or "awful", a sense Owen never intended.
Dinosaurs lived on every continent, including Antarctica. This does not mean that dinosaurs lived in polar wastelands. During the time of the dinosaurs, the world was much warmer, and Antarctica had forests. Dinosaurs also lived in many different Mesozoic environments, including deserts, forests, and coastal swamps.
The dinosaurs from the Mesozoic Era lived from 230 to 65 million years ago, from the Late Triassic Period through the Late Cretaceous Period. The dinosaurs from the Cenozoic Era (most birds, which are a subgroup of theropod dinosaurs) lived from 65 million years ago to today.
If you find what you think is a dinosaur bone, this is what you should do.
Leave it where it is, even though it's tempting to take it home. Instead, take a picture of it, mark its location on a map, and tell someone at a natural history museum. They will use tools that allow the fragile fossil to be safely collected.
If your wondering "what are the best sources for info on dinosaurs" then here they are.
The library (first and foremost!), followed by natural history museums (second), then the internet, and finally (and certainly last) TV programs.
There's over 1000 Mesozoic (non-bird) dinosaurs have been given scientific names since 1824 when the first dinosaur was named. About half of all the dinosaurs named may not be valid because they were given names based on bits and pieces that do not stand up under modern scientific tests. Nonetheless, it has been estimated that fewer than 10% of all the dinosaurs that actually existed have been found. This is because the fossil record is not complete, and many rocks from the Mesozoic Era are still buried where we cannot get to them. In addition, many dinosaurs must have lived in environments where fossils did not form, so we have no record of them at all.
If your wondering "why dinosaurs were so big" these are the answers.
There are several reasons: Size is the best defense. Dinosaurs, like several groups of reptiles, had indeterminate growth - which means they continued to grow throughout life, as long as they were healthy and had access to food. Dinosaurs laid eggs, and did not have to nurse their young (like mammals), so they could devote more of their biological "energy budget" to growth.
If your wondering " Are dinosaurs extinct?" this is the answer.
Yes and no. All the dinosaur species that lived during the Mesozoic Era are extinct. And all of the "traditional" dinosaurs (meaning all the dinosaurs that aren't birds) are extinct. Seven of the eight major groups of dinosaurs are extinct, leaving only the theropod dinosaurs (see above). One of 40+ subgroups of theropod dinosaurs evolved into birds, so that one major group is not extinct. You can say that dinosaurs are 7/8 extinct!
My favoite dinosaur - the Spinosaurus.
Special thanks to Smithsonian for the info!