Prehistoric Animals

Prehistoric Animals.
What Is a Prehistoric Animal?. Prehistoric animals are all organisms that walked—or swam, crawled, slithered, or flew—on Earth more than 5,500 years ago, before humans started recording history. The earliest known remains date to the Cambrian era, about 600 million years ago, although simple-celled organisms have been around much longer. Crustaceans, flying reptiles, dinosaurs, woolly mammoths, and saber-toothed tigers are just a few of the hundreds of millions of prehistoric animals that once lived on Earth. Paleontologists know about these animals by studying fossils, animal remains that have been preserved in rock. Prehistoric animals represent the vast majority of extinct animals. Thru Paleontological exploration, scientists are slowly piecing together evolution from the fist sea dwelling organisms to present day species. There will always be much speculation as to what caused the extinction of the dinosaurs.

Also see: Walking with Dinosaurs

Below is a chart indicating the various eras and periods, as well at the species which were first introduced at the time.

Era	Cenozoic	Mesozoic	Paleozoic
Period	Quaternary First Humans 3 to 0 Million Years Ago. From the Ice Age to the Appearance of the first human beings.	Cretaceous Dinosaur Birds Mammals 144 to 65 Million Years ago. Last part Of the age of Dinosaurs	Carboniferous Amphibians Early Reptiles 360 to 248 million years ago. Appearance of the first reptiles (laying their eggs on land).
	Tertiary Dinosaur Extinction 65 to 3 Million Years Ago. Dinosaurs inexplicably become extinct and mammals and birds become the dominant species.	Jurassic Dinosaurs Birds Mammals 206 to 144 Million Years ago. This is the high point of the dinosaur age, there are a great number of species including giant plant eaters. Appearance of the first feathered birds.	Devonian Amphibians Fish 408 to 360 Million Years Ago. Appearance of the first amphibious creatures.
		Triassic Dinosaurs Mammals 248 to 206 Million Years Ago. Appearance of the The first dinosaurs and the first mammals.	Silurian Fish 438 to 408 Million Years Ago. Plants begin to cover the land.
			Ordovician Marine Invertebrates Fish 505 to 438 Million Years Ago. The Oceans are teeming with invertebrate life. Appearance of he first true fish.
			Cambrian Marine Invertebrates 570 to 505 Million Years Ago. Appearance of the first marine invertebrates.

The fossils show us what was alive during that time but the prehistoric art left by primitive humans shows us what the fossils cannot - what the animals looked like WHEN ALIVE! For example, while we know from fossils, that the Cave Lion (Leo spelaea) existed with primitive humans, we can see from Cro-Magnon cave art that these fearsome beasts had tufted tails, tiger-like stripes and short, partial manes - features we never would have known from simple bones. To better understand primitive humans, we must look at the world in which they lived in - a much different world in which we live today. Even the climate and fauna as recently as the ancient Romans and Egyptians was much different than it is now. We know this from ancient artwork and manuscripts of their time, describing their world filled with animal and plant life that no longer exists in regions where it once flourished.
Each of the prehistoric animals featured here played a vital part in the lives of prehistoric humans. In some cases, Man was the hunter - in others, Man was the HUNTED! Some of these beasts were even revered by Man and quite possibly, played a lead role in the earliest form of human religion. Of course, we have no written record from the prehistoric past describing what the world was like but we have two intriguing and invaluable types of evidence to allow us to recreate that time - FOSSILS and PREHISTORIC ART. Both of these pieces to the puzzle are important.

Source : World Museum of Man
National Geographic