Individual Bones

Here's a little bit of information about some of the individual bones of Kathy Wankel's T. rex skeleton that we've cleaned and that Kit Mather has illustrated. We've

Tyrannosaurus Rex Arm Bones
humerus: the size of this arm bone suggests it was used for something, and so do its very distinctly marked muscle insertions, we thought it was pretty massive, but compared to "sue" it turns out to be rather light.

already mendoned a lot of the skull bones, so let's start at the back of the head and work our way down.

Occipital Condyle

A special swivel joint connected T. rex's skull to the adas, or first neck vertebra. This adas vertebra fitted into a big ball on the back of the skull, the occipital condyle. On us it's just a little knob, but on T, rex it was the size of a small grapefruit. We have a double condyle (the ball fits into an axis vertebra on the other side), which limits the motion of our necks. T. rex, like birds, had only one. T. rex's head was tilted forward and down when in a relaxed position. But with a single condyle, a long neck,

Rex Head Only

and powerful neck muscles, T. rex could swivel and look behind as well as ahead.

Neck Vertebrae and Cervical Ribs

The neck bones of T. rex have big prongs on them, called neural spines. These are the attachment points for huge muscles that link up on the other end to the top of T. rex's head. The small size of the neck bones compared with the massive head they supported suggests that T. rex must have had massive neck muscles. What other benefit would those neck muscles have provided? Feel the back of your neck when you're biting down and pulling on a piece of taffy. Those muscles on a T. rex would have been useful for yanking at food.

Below the prong on each vertebra of T. rex and other dinosaurs is the rest of the neural arch. Pairs of big facets that rise vertically above the spinal cord on the front and back of each arch are called zygapophyses. They are the points at which each back vertebra is linked to the next. The space between the large zygapophyses of adjacent vertebrae on T. rex's neck helped make its neck very flexible.

Neck Tyrannosaur
pat leiggi takes a turn at preparing the vertebrae of the wankel t. rex.

cervical ribs the complete t. rex


Big ribs wrap around T. rex's neck. These huge bows of bone (along with the neck muscles) would have protected T. rex's windpipe from attack. They were the attachment points for many muscles controlling the position and movement of T. rex's neck.

Dorsal Vertebrae

The back vertebrae where the ribs attach look like coffee cans. They're huge—and they had to be to hold the big ribs coming off them and a huge stomach. Stomachs aren't preserved, but on an animal this size, a full belly could have been holding five hundred pounds of meat.

Tyrannosaurus Bones


The pubis is composed of two huge bones (left and right) that sometimes fused, with a bootlike end that hung down and forward from the pelvis. It's big enough that if T. rex got down on its knees, it could have rested on its pubis. I'm not saying it did sit this way, but the pubis at least makes this position possible.


A pair of these pelvc bones stick out backward. The ischia (plural) could have supported the reproductive opening, the cloaca. And they may have been a platform for attachment of big muscles of the tail.


The third and biggest of the paired bones of the pelvis are the ilia (plural). Each ilium has a tall blade for the attachment of what might have been the biggest muscle on a T. rex's body, the thigh muscle. (The femur bone fits into a big hole at the juncture of the ischium, ilium, and pelvis called the acetabulum.) This huge muscle sheet formed a triangle that attached to the femur. Similarly thick thigh muscles are one of the reasons you don't see the femur bone on a chicken—they're the thigh meat. And birds' thigh bones are short and carried horziontally. If you lived with T. rex, you probably couldn't have seen much of T. rex's thigh bone either.

Tibia and Femur

T. rex's upper (femur) and lower (tibia) leg bones are much longer than those of far earlier meat-eaters like Allosaurus. T. rex's svelte limbs are stubbier proportionately than those of the ostrich-mimic ornithomimid dinosaurs. Fast dinosaurs like ornithomimids had lower leg bones that were longer than those of their upper legs. That's true of other fast animals like cheetahs. But the drumstick bone, the tibia, is about the same length on T. rex as its thigh bone, the femur. The fact that these bones were so close in length on T. rex is one of the strongest indications that this animal couldn't run very fast.


While it had only two fingers, T. rex had three toes (and a gready reduced first digit)—the second, third, and fourth toes of an ancestral five-toed foot. Our five toes


While it had only two fingers, T. rex had three toes (and a gready reduced first digit)—the second, third, and fourth toes of an ancestral five-toed foot. Our five toes

above: t. rex's toes were big and extended the size of its foot considerably.

greg paul and bob bakker suggest that long toes helped in swimming, but duckbills had short, flat feet, and they were good swimmers. deer swim well, and they have tiny toes. t. rex's toes were powerful. but it's hard to say if that power was used for swimming. running, or tearing up meat.

and fingers are primitive characteristics in animals. When it comes to feet, dinosaurs were more advanced than we.

The middle toe is the largest and the principal weight-bearing one for T. rex. Like the short front teeth that it had in common with Troodon, the pinched third toe is a characteristic that suggests tyrannosaurids may have been descended from an ancestor of those small predators.

Tail Vertebrae

Our T. rex skeleton has only seventeen of what would have been at least thirty-five tail vertebrae on T. rex. The tailbones we have are conservative in form, much like those of earlier tyrannosaurids. They're huge bones too, even bigger than those of the neck. They show projections that might have provided support to keep the tail raised horizontally, though none to limit its moving side-to-side.

Put all these bones together and you have the beginnings of an understanding of how T. rex looked and moved. And by comparing our T. rex not only to other T. rexes, but to discoveries, some of them just as new, of carnivores that came before T. rex, we can begin to figure out how T. rex came to be.

chapter 6

+1 0


    What is the size of a tyrannosaurus rex leg bones?
    7 years ago
  • Erkki
    Does a t rex have a foward facing pelvic bone?
    12 months ago
    What does a piece of prehistoric skull look like?
    3 months ago

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