Although a number of dinosaurs, including some of the best known, were huge, most were not. The average size of a dinosaur was little bigger than that of a modern sheep.
To date, about 860 different types of dinosaurs have been named.
Because fossils form only under certain conditions, and because many dinosaurs probably lived in environments where these conditions did not apply, no fossils have been found as clues to the existence of these dinosaurs - and no one knows how many of these "missing" dinosaurs there might be.
The Stratigraphic Column
This is a register, or diagram, of the relative ages of different types of rocks.
The stratigraphic column spans almost the full 4,600-million year history of the world.
In order to make it easier to understand, geologists have divided the column into a number of different sections: eras, periods and epochs.
Times are calculated by looking at the degree of decay that is displayed by particular elememys found in certain tyypes of rocks. The longer the rock has been in existence, the greater the decay that will have taken place.
From the OLDEST to the Youngest
Early Paleozoic
Cambrian
Ordovician
Silurian
Late Paleozoic
Devonian
Carboniferous
Permian
Mesozoic - the age of dinosaurs
Triassic
Jurassic
Cretaceous
Cenozoic - Ascendancy of mammals and mankind
Paleocene
Eocene
Oligocene
Miocene
Pliocene
Pleistocene
Holicene - Now
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Bibliography
A Guide to Dinosaurs, edited by Michael K. Brett-Surman, Fog City Press, 1997
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