Most of what we know about dinosaurs, including how big or how small they were, comes from their skeletons. In order to understand dinosaurs, we need to learn how skeletons are put together. And luckily, we have a great learning resource close at hand, and that's our own skeletons. Dinosaurs and humans have basically the same skeletons with all the same bones in the same places. They may be used for different purposes and therefore shaped in slightly different ways, but they're the same bones. Because dinosaurs and humans belong to a group of animals called vertebrates and we all have a common ancestor. >> Humans are vertebrates, but what do you think the word vertebrate refers to? Only one answer is correct. Is it A, teeth, B a backbone, C a heart, or D, legs? The word vertebrate refers to the presence of vertebrae, or the individual bones of the backbone. Vertebrae are a line of bones that form the spine of fish, amphibians, reptiles, birds and mammals. So B is the correct answer. We will talk about evolutionary theory, and the evolution of dinosaurs in more detail in later units of this course. But in order to talk about dinosaur anatomy, we need to know a little bit about the evolution of animals. Think about evolutionary relationships between animals as a branching tree. Like a family tree, with the most primitive ancestral forms at the trunk, evolving into more derived species on the branches. Dinosaurs belong to a branch called the Vertebrata, or, vertebrate animals. Which of these animals do you think are vertebrates? Your choices are: an octopus, a shark, a human, or a snake. Check all the answers you think are correct. All of these animals are vertebrates, except the octopus which is a type of invertebrate related to clams. Sharks have cartilages rather bony backbones, snakes also have backbones even though they lost their limbs over the course of their evolution. And of course we humans have backbones as well. So the correct answers are B, C, and D. All vertebrates have skulls and backbones. Invertebrates have neither. Examples include insects, which have exoskeletons, and jellyfish, which have no skeletons at all. The basic form of the vertebrate skeleton evolved more than 300 million years ago. But this form has been modified for numerous purposes, as animals have adapted to various lifestyles. The basic arrangement of bones in the body is similar among all vertebrates, because they evolve from a common ancestor. The shapes and proportions of bones can tell us a lot about what kind of vertebrate we are looking at, and what adaptations it has. It's easy to see the differences between the skulls of a living wolf, a mountain lion, and a harbour seal. Looking at the bones of modern animals helps us to understand what bone shapes mean in terms of function and adaptation. Let's start with the top of the skeleton, the skull. Rather than being a single bone, the skull's composed of many, many bones. Skulls come in a wonderful variety of shapes and sizes, that reflect adaptations for feeding and senses. You won't need to know all of the bones of a skull, but you should be familiar with the general layout, and some of the important features. The openings for the eyes are called orbits. And the openings for the nose are called nares. Other openings in the skull are called Fenestrae, which means window. And these are important for distinguishing between major lineages of vertebrates. Skulls of mammals, like this coyote, only have one fenestrae behind the orbit. Located here, with this being the orbit. And they have no Fenestrae infront of the orbit. Also located at the front of the skull, are the nares. However, this small tyrannosaurus skull has two holes behind the orbit. The first one being the Supratemporal. And the other one, the Laterotemporal Fenestra. And they also have one in front of the orbit, with the orbit being here, and this one is called the Antorbital Fenestra. In front of the skull is the nares. The brain is housed in a box called the brain case, with openings for nerves that send messages to the rest of the body, including the spinal cord. Teeth can be found in the upper and lower jaws. When you move on from this video, you'll have your first experience with your very own 3D fossil viewer. Go ahead and check it out. You'll be able to look at your own version of a tyrannosaurus skull. Just open up the specimen cabinet and you'll find the fossil there. >> Now that you've had a chance to look at the tyrannosaurus skull in 3D, take a look at this dinosaur skull and see if you can find the similar features on it. Please tick the box over the antorbital fenestra. The hole nearest the front of the skull is the naris, where you will find the animal's nostrils. Working our way back from the front of the skull, comes the location of the correct answer. The Antorbital Fenestra. Next in line, is the orbit, where the eye is located. Behind the orbit is the lateral temporal fenestra. Not seen in this image, is the super temporal fenestra, which is located on the top of the skull here. >> Your backbone or spinal column, is composed of many small bones called vertebrae. This is the dorsal vertebrae of an edmontosaurus. And each vertebrae has a disc like centrum and many prosthesis for muscle attachment. You can see the hole where the spinal cord fits. The vertebrae in your neck are different from the ones in your back. The vertebrae in your pelvis fused to the hip bones to form a solid structure. Although we don't have tails, tails are composed entirely of vertebrae. Neck vertebrae are called Cervical, back vertebrae are Dorsal, hip vertebrae are called Sacral, and tail vertebrae are Caudal. Ribs articulate with the vertebrae. Mammals are unusual because we don't have ribs in the rear portion of our body, but dinosaurs had ribs all the way to the pelvis. Another difference between mammals and dinosaurs, is the presence of gastralia, or belly ribs, which aren't found in mammals. The shapes of vertebrae represent adaptations for flexibility and posture. Your arms and legs connect to the rest of the body via the limb girdles, the shoulder girdle, and the hips or pelvic girdle. The shoulder blade, or Scapula, is where your shoulder socket is located. The hip socket is called the acetabulum. Now we know about the arms, legs, shoulders and hips, but let's think about the adaptations and functions of limbs. The shapes and proportions of bones in our body can represent adaptations to our environment. There're many kinds of adaptations we can see in arms, legs, shoulders and hips. The most important of these are adaptations for moving around. For walking, running, flying, swimming, or jumping. Was a particular dinosaur a fast runner, or a slow plodder? Did it fly or swim? Looking at the limbs will help you answer these questions. We can also look at the arms and legs to help us understand a dinosaur's place in its ecosystem. Did it have sharp claws or grasping hands? Then it might have been a predator. Did it have long legs? Then it might have been a really fast runner. >> As we mentioned, the bones of different animals may take different shapes, but the same kinds of bones will be present. For example, here we have a human and a tyrannosaurus arm. The main bones of the human arm are labeled. Which bone on the Tyrannosaurus arm is the ulna? Good work. The same arm bones are present in both humans and Tyrannosaurus. There are some obvious differences. The Tyrannosaurus arm is much bigger, and it only has two main fingers, compared to our five. But the underlying structures of the humerus, radius and ulna, and metacarpals, are shared. Although dinosaurs and mammals are not closely related, a human arm has the same bones as those of a tyrannosaur. This is a cast of the right arm of a Tyrannosaurus Rex. The upper bone is called the Humerus. It corresponds exactly to the location and function of the humorous in our arms. It supports two bones on the forearm, the radius and ulna, which in turn attach to the wrists. The bones in the palm of the hand and the fingers are exactly the same as we find in humans. Even though this dinosaur is missing a few bones. Over the course of evolution, the two outer fingers in Tyrannosaurs became smaller and smaller, eventually disappearing completely. We can see the same thing happening to the middle finger, which is represented by a small thin bone in the palm of the hand. The proportions and shapes of the tyrannosaur arm bones are a little bit different than those in the human arm. In particular, Tyrannosaurus rex had large claws on the fingers. Whereas humans have replaced the claws with fingernails. Differences in the numbers, sizes and shapes of bones, help us to differentiate one species from another. Now, we're looking at the leg bones of Tyrannosaurus rex. However, it does not matter which dinosaur we look at, because the leg bones are all basically the same in vertebrates. We humans have the same bones in our legs as well. The upper leg bone of Tyrannosaurus Rex, which is the same one in my leg, is called a Femur. The two lower leg bones are known as the Tibia and Fibula. If you've ever broken your leg, most likely you broke your fibula. The ankle bones are small and support the longer ones in the sole of the foot. Like humans, this dinosaur has five toes represented in its foot. The inside or first toe is small and does not touch the ground. Three toes, the second third and fourth, support the animal's body weight. The fifth or outer most toe was lost. Although it's still represented by a splint like bone in the sole of the foot. Like most dinosaurs, all Tyrannosaurus walked on their toes and the soles of their feet were elevated off the ground. Now you know something of vertebrate skulls, backbones, and limbs. It's time to put your knowledge to work. When you leave this video, you'll be taken to an interactive puzzle. You're going to try and build a complete tyrannosaur skeleton. We'll place the hip bones for you, but the rest of the bone groups can be moved around by you. Start at the hips, and work your way out to build the entire skeleton. Good luck. Your tyrannosaur skeleton looks great. The skull is connected to the cervical vertebrate in the neck, then the dorsal vertebrate in the back, then the sacral vertebrate are fused to the hips, followed by the cotal vertebrate of the tail. There're ribs and gastralia in the right places. The shoulder girdle leads down to the humorous, radius and ulna and hands. The hips are also in the right place, and then the femur leads down to the tibia, and fibula, and feet.