Contents What is a dinosaur? If dinosaurs were reptiles, they were cold-blooded, right? How do people know so much about dinosaurs? When did the dinosaurs live? Did dinosaurs fly? Sauropods Theropods Was the Tyrannosaurus as fierce as it's shown to be? Ornithopods Marginocephalia Plated and Armoured Dinosaurs Pterosaurs Marine Reptiles

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.

If dinosaurs were reptiles, they were cold-blooded, right? Yes, that would make sense, but people are actually still debating on that. On one hand, every reptile we know about today are cold-blooded, so it would make sense if dinosaurs were too. On the other hand, trace fossils of dinosaurs show that they led a very active lifestyle (Well of course, if they were always chasing and killing, or being chased and killed by other dinosaurs.). Cold-blooded animals wouldn't be able to do that, because they need the sun to warm their blood and give them energy. They'd need to lay in the sun all day, which probably wouldn't be a good idea if they wanted to continue living. People debate about this lots, but no one really knows. So, this is another one of those things where you get to decide. Pick one, and if the teacher says you're wrong, well, there's not really much you can do to convince those teachers, is there?

How do people know so much about dinosaurs? Actually, very little is known for certain about dinosaurs, considering all of our knowledge is based on little fragments of rock. That's right, everything we know about dinosaurs came from our study of fossils. If you read the section on fossils, you will know that there are regular fossils, and trace fossils. Both of them help us to learn about the way dinosaurs looked and acted. Fossils tell us how big an animal was, and their relative shape. Trace fossils can help to show us the way dinosaurs acted. Those are very important, but fossils cannot tell us other important things, such as colour, and some behaviours. Scientists make estimated guesses on these things by comparing dinosaurs with other living things that we know more about. A dinosaur with sharp teeth and claws ate meat, and dinosaurs with blunt teeth and strong jaw muscles ate plants. If we know the habitat in which the dinosaurs lived in, we can guess on their colour. Animals tend to have colours similar to their surroundings so that they can blend in and not be noticed. We can figure out a dinosaurs behaviour by looking at the behaviours of modern animals who are similar to them in diet, habitat and size. By understanding how organs and muscles are distributed throughout the body, we can draw out what the dinosaurs would probably have looked like while still alive. That, is how we can learn so much about animals that have been dead for millions of years.

When did dinosaurs live? It is very clear that there are no more dinosaurs around today. You probably also know that they lived a very long time ago. (Back when your teacher was young, lol) How long exactly though? Not hundreds of years ago, not thousands, and definitely not billions or trillions. Actually, the last dinosaur died out approximately 65 million years ago. The dinosaurs lived during the Mesozoic Era which contained the geological periods Triassic, Jurassic, and Cretaceous, in that order, with the Triassic coming first. The first primitive dinosaurs evolved onto this planet 248 million years ago.

Did dinosaurs fly? The answer is simply "no". If it flew, it was not considered a dinosaur. No dinosaur ever flew, none ever will. The flying creatures that people very often mistake for dinosaurs were the Pterosaurs. Even though they were very closely related, Pterosaurs were not dinosaurs, they were a class all of themselves.

The Sauropods The Sauropods were a group of herbivorous dinosaurs that had long necks, small brains, and large tails used for a counterbalance. The word Sauropod means "Lizard Footed". They had thick, five-toed legs, blunt teeth, and nostrils very close to their eyes, which lead some scientists to believe that they sometimes went underwater. If you still don't know what I'm talking about, these dinosaurs are sometimes referred to as "Long Necks" thank you very much The Land Before Time. Do you ever notice how Littlefoot seems to be getting smaller? Anyway, that's off topic. The Sauropods evolved in the Jurassic period from the Prosauropods. They ate mostly conifers, since those were the dominating vegetation at the time. They all had very long necks, and were quite large animals. Their necks could have had a variety of uses. Some people think that they used them to reach leaves high up in the trees where no other dinosaurs could reach, like giraffes do today. Some Sauropods, like Diplodocus, held their necks in a more horizontal stance, while some, such as Brachiosaurus, held their necks straight up. As I mentioned before, some scientists think that, because they had long necks and nostrils on the top of their heads, they could occasionally escape into the water when chased by predators, or they could have stayed underwater all day feeding on underwater plants. Other scientists doubt this, saying that, since it had such a long neck, it would be very hard to breathe at such depths. A Brachiosaurus painted by Joe Tucciarone The Sauropods ranged in size from 2-3 metres long, to over 30 metres! One thing that has puzzled scientists is the fact that they have such a tiny brain for their massive size. It's not like they had to go to school or anything, but they had a very large body to control, and it doesn't seem possible that the job could be done by an area the size of a tennis ball. It was once though that Sauropods had another brain at the base of the tail. We now think that it is probably an enlargement in the spinal chord containing nerves and fatty tissue. It may have been used to control the tail and hind legs. Some major groups of Sauropods were: Diplodocids (meaning "Double Beams") - They had a small head, whip-like tail, very long neck, and pencil like teeth. They lived from the late Jurassic to the end of the Cretaceous. Some examples of them are: Diplodocus, Apatosaurus, and Amargasaurus. Brachiosaurids (meaning "Arm Lizards") - Their stance much resembled a giraffe, with their front legs longer than their hind legs. They had a short, thick tail, with teeth like chisels and nostrils on the top of their head. They lived from the mid-late Jurassic to the early Cretaceous. Some examples are: Brachiosaurus, Sauroposeidon, and Ultrasauros. Camarasaurids (meaning "Chambered Lizards") - Compared to other Sauropods, they had a relatively short tail and neck. They had hollowed-out chambers in their vertebrae, hence the name. There head was quite large and box-like for a Sauropod, and they had chisel-like teeth all along their jaws. their nostrils were ahead and just above the eyes, and they lived from the late Jurrassic to the end of the Cretaceous. Some examples are: Camarasaurus, Algoasaurus, Aragosaurus, and Asiatosaurus. Titanosaurids (meaning "Titanic Lizards") - They had armoured skin, sometimes even horns and bony plates. They had a wide head and peg-like teeth. These dinosaurs lived from the late Jurassic to the end of the cretaceous. Examples are: Titanosaurus, Aegyptosaurus, Aepisaurus, and Alamosaurus. Cetiosaurids (meaning "Whale Lizards") - Their vertebrae was almost solid, and they also had a shorter tail. Lived from the early Jurassic to the middle Cretaceous. Some examples are: Cetiosaurus, Amygdalodon, and Austrosaurus.

Theropods Theropods, (meaning "beast footed") were a group of quick-moving carnivores. They had grasping hands, and claws on their "fingers". They ranged greatly in size, and included most of the meat eating dinosaurs, like chicken-sized Compsognathus, and the famous Tyrannosaurus. They walked upright on two feet, and had sharp teeth for tearing flesh. Their arms were short, as to grasp prey with. They lived from the mid-Triassic to the end of the Cretaceous. They were fast and had good eyesight, for hunting.

A pair of Deinonychus painted by Joe Tucciarone

Was the Tyrannosaurus as fierce as it's shown to be? Everyone loved the part in Jurassic Park when their Tyrannosaurus went haywire and swore an oath to terrorize humans his whole life, no matter what, resulting in a few people getting shredded. Even though my little fight with Jurassic Park is besides the point, some experts highly doubt that the Tyrannosaurus was even close to being that fierce. It had very small, very useless forearms. It was just like your arms being the size of your fingers on you. With such a burden as this, it would be very hard to take down prey. Plus, if the animal ever fell down, it would have a hell of a time getting back up. Also, it was so massive, it would have a hard time sneaking up on the other dinosaurs in order to kill them. Scientists think that it was too dumb, too. it's brain size is very small, compared to other Theropods, who were much more intelligent. Instead, scientists are now beginning to believe that Tyrannosaurus might have been a scavenger, feeding on the remains of other kills, as opposed to a hunter. So does this mean that Littlefoot's mother should have lived? Other scientists disagree. Using a model of a Tyrannosaurus head, one Paleontologist mapped the range of a Tyrannosaurus' vision. It was comparable with that of hawks, meaning that it hunted. Once again, this is one of the great things about paleontology. There are always things we are unsure about, and always more to find out.

A Tyrannosaurus painted by Joe Tucciarone

Ornithopods The name Ornithopod means bird feet. They had a beak, and they either walked on two legs or two legs sometimes and four legs sometimes. they had no body armour, and lived from the Triassic to the Cretaceous, and they had no hole in their outer, lower jaw. Ornithopods included: Heterodontosaurids - small, early dinosaurs with three kinds of teeth Hypsilophodontids - small, fast-running dinosaurs with self-sharpening teeth and a small beak Dryosaurids - small, fast-running dinosaurs with a long, stiff tail Thescelosaurids - late, fast-running dinosaurs Camptosaurids - beaked dinosaurs with hoof-like claws Iguanodontids - beaked dinosaurs with hoof-like claws and a spike on each thumb Hadrosaurids - large duck-billed dinosaurs with no head crest Lambeosaurids - large duck-billed dinosaurs with a head crest The above definitions quoted from http://www.enchantedlearning.com/subjects/dinosaurs/ Hadrosaurs is the group of Ornithopods commonly know as Duckbills.(yep yep yep!) The word hadrosaur means "bulky lizards". Some duckbilled dinosaurs had a crest on the top of their heads, they were called Lambeosaurinae (ones with no crests were called Hadrodsaurinae). Scientists think that air was blown through the hollow opening in these crests to make loud noises, probably for dominance and warning. Hadrosaurs were the most common dinosaur, and they probably grazed in large herds, like zebras or wildabeast today. They walked mainly on two feet, but on four feet when they grazed. They had toothless beaks, but up to 960 cheek teeth! The most teeth for any dinosaur! They also had a stiff tail used for balance, nails on their feet, and bumpy skin. They lived only in the late Cretaceous period.

A Parasaurolophus painted by Joe Tucciarone

Marginocephalia The special thing about Marginocephalia ( meaning "fringed heads") is their distinctive skull structure. They have a shelf or bony frill at the top of their skull, and a unique palate (part of the mouth). They ate plants. There were two groups of Marginocephalia, the Ceratopsians, which were horned dinosaurs, such as Triceratops, and Pachycephalosaurians, skulled dinosaurs that walked upright.

A Triceratops painted by Joe Tucciarone

Plated and Armoured Dinosaurs When people think of plated dinosaurs, they think about Stegosaurus, and other dinosaurs with a double row of plates on their back. These dinosaurs evolved during the Jurassic Period. The many plates or spines these dinosaurs had may have been used for defence, or they may have been used to regulate the creatures body tempature (like a rabbit does with it's ears). The Armoured dinosaurs, such as Ankylosaurus, evolved during the Cretaceous period. They had bodies shaped like a barrel, and backs covered in armour. Kind of like a tank. The following definitions, quoted from http://www.gridclub.com/fact_gadget/prehistoric_life/ prehistoric/plated_and_armoured_dinosaurs/2300.html describe some of the different types of plated and armoured dinosaurs. (A) LOW PLATES Wuherosaurus, from China, had plates that were long and low. But it did have some fierce spines along its tail. (B) THE SPINIEST Kentrosaurus had long spines and very narrow plates. It had a pair of spines that stuck out over its hips. (C) THE BIGGEST Stegosauru was 7.3 metres long and was the biggest of the plated dinosaurs. This dinosaur is also one of the best known. (D) SMALL PLATES Another Chinese form, Tuojiangosaurus, had small conical plates all along its back. All armoured dinosaurs were plant eaters. Some of them had spikes at the end of their tail, or a big club, to defend themselves. The plated dinosaurs were vulnerable on their neck, and the armoured ones' weak spot was their soft underbelly.

A Stegosaurus painted by Joe Tucciarone

An Ankylosaurus painted by Joe Tucciarone

Pterosaurs Even though I have already explained that Pterosaurs were not dinosaurs, I will still tell a little bit about them. Typical Pterosaurs had lightweight, leathery wings, and a furry body. There wings were attached to incredibly long fingers. The short-tailed pterosaurs were more advanced. They had long wrists and short tails (duh!). Lastly, the long-tailed pterosaurs were the most primitive. They had short wrists and, long tails. Pterosaurs could get quite large. The largest one was Quetzalcoatlus, who had a wingspan of 11.8 metres. That's as big as a small airplane! It looked like a Pokemon. Different Pterosaurs also had different diets. Some had strainer-like teeth, and they fed on small crustaceans like flamingoes do. Some flew over the water and caught fish, while others ate insects.

A Quetzalcoatlus painted by Joe Tucciarone

Sea Reptiles Even though they, too, were not real dinosaurs, a lot of interesting reptiles lived in the sea during prehistoric times. There were two important groups of marine reptiles, the plesiosaurs and the ichthyosaurs. The plesiosaurs were dived into two groups, long-necked, and short-necked. The long necked kind looked like swimming Sauropods, while the short-necked kind sort of resembled whales. They all had very sharp teeth and were very scary. The Ichthyosaurs looked like evil dolphins from hell, and like to stare at people in the museum. All these marine reptiles were very large and ate fish, ammonites, and each other. They were not fish however, so they had to come to the surface to breathe.

From left to right: Ichthyosaur, Long-necked plesiosaur, Short-necked plesiosaur.

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