What is a dinosaur?
The word dinosaur means “terrible lizard”. Dinosaurs were reptiles, meaning that they had no fur and hatched from eggs. They were closely related to lizards, but were really very different. There are many differences, but the main one lies where you’d least expect it. It is the way their legs join to their hips. It sounds funny, but if you think about it really, it is true. If you look at a lizard, you’ll notice that their legs are in a kind of squatted position, with the legs going out to the side. A dinosaurs legs, however, go straight down, much like our own. So, that is how you can tell the difference between a dinosaur and a lizard, if you should ever encounter one, or if it is a question on Jeopardy.
Millions of years ago, long before there were any people, there were dinosaurs. Dinosaurs were one of several kinds of prehistoric reptiles that lived during the Mesozoic Era, the “Age of Reptiles.” Dinosaurs were reptiles and most hatched from eggs. No dinosaurs could fly and none lived in the water. Plant-eating sauropods were the largest animals to ever walk on Earth – but blue whales are more massive than any of the dinosaurs were! The largest dinosaurs were over 100 feet (30 m) long and up to 50 feet (15 m) tall (like Argentinosaurus, Seismosaurus, Ultrasauros, Brachiosaurus, and Supersaurus). The smallest dinosaurs, like Compsognathus, were about the size of a chicken. Most dinosaurs were in-between. It is very difficult to figure out how the dinosaurs sounded, how they behaved, how they mated, what color they were, or even how to tell whether a fossil was male or female. No one knows what color or patterns the dinosaurs were. Most dinosaurs were plant-eaters (also called herbivo
Dinosaurs are a group of terrestrial reptiles that first appeared in the Late (or perhaps Middle) Triassic Period, about 230 million years ago. Although dinosaur bones have been discovered throughout human history, these animals were only described scientifically in the early nineteenth century. Since that time, scientists have identified nearly a thousand different dinosaur species, from all continents, and ranging in size from a few kilograms to tens of tons. Dinosaurs are also a popular and evocative group of animals, familiar to children and adults around the world. For a century they embodied the concepts of failure, sloth, and obsolescence, but the recent renaissance in dinosaur paleontology has led us to understand them as active, successful organisms that dominated terrestrial ecosystems for over 160 million years.
Dinosaurs were reptiles that lived through three periods of Earth’s geologic history: Triassic (208-245 million years ago), Jurassic (145-208 million years ago), and Cretaceous (65-145 million years ago). Different species of dinosaurs flourished and then became extinct throughout these three periods. All dinosaurs were reptiles, but not all reptiles were dinosaurs. Even though the name “dinosaur” means “terrible lizard,” dinosaurs were not lizards at all. Some Key Dinosaur Facts • All dinosaurs had four limbs. Some walked on all four legs; others, on their two back legs.
