DINOSAURS INSIDE AND OUT

GROWING BONES

Why are fossil bones important to our understanding of dinosaurs?

The study of fossil bones is extremely important to our understanding of dinosaurs because, in most instances, this is the only way to obtain knowledge about these animals. Other than footprints and rare fossil remains of skin, eggs, and certain (rarely found) petrified internal organs, dinosaur fossilized bones (and teeth) are the most common parts that survive over long spans of time. Depending on the way the bones lie within the rock strata, they provide important clues as to how these animals looked, ate, walked, socialized, lived, and, in some cases, died.

What does the dinosaur skeleton tell us about the animals soft parts?

There are several ways in which scientists interpret soft parts based on a dinosaurs skeleton. For example, some muscles leave attachment scars on well-preserved bones. The size of an animals skull sometimes tells us the relative size of the brain.

The holes and hollow spaces in the bones could indicate pathways for nerves. Most importantly, the comparison of dinosaur bones to those of living animals can give us a good idea of the size, anatomy, strength of certain dinosaurs, and sometimes the internal configuration of a dinosaurs organs.

What is the composition of most dinosaur bones?

Most dinosaur bones, including teeth, are made of calcium phosphate, a material that is very hard and resistant to destruction. This explains why many dinosaur bones survive in rock layers. Those bones that didnt survive were usually destroyed by certain geologic processes. For example, many were crushed by moving rock (from earthquakes or volcanic eruptions), or dissolved by naturally occurring acidic water moving through cracks in the rock.

How does bone composition differ between dinosaurs and modern reptiles?

The bones of a dinosaur and a modern reptile are very similar, with few minor additions or subtractions to bone composition over the millions of years of evolution. Scientists determine this by analyzing specially prepared bone tissues. The tissues are embedded in a synthetic polymer, sectioned, and ground to the right thickness; then they are thinly coated in carbon for analysis in a scanning electron microscope (SEM).

In one instance, the bones of a modern alligator and a Tyrannosaurus rex were compared using an SEM with an energy dispersive X-ray (EDX) analyzer. The results showed that both bones had calcium and phosphorous as their major elements, with both elements present in the same ratios in ancient and modern bones. Some trace elements, such as magnesium, aluminum, silicon, and sodium, were also present.

Did dinosaurs differ in bone structure?

Overall, each dinosaur had a skeleton made up of the same basic structures: the skull, spine, ribs, shoulders, hips, legs, and tail. But individual dinosaur fossil bones do have structural differences. This is apparently dependent on several factors, including where the bones were located in the dinosaur, the bones purpose or purposes, and the species of dinosaur. In general, dinosaurs that depended on speed needed long, light bones, while larger, slower-moving dinosaurs needed strong, solid bones.

Some of the best examples of the differences between dinosaur bone structures are seen in the bipedal and quadrupedal herbivores. The large, heavy sauropods walked on all fours; they needed strong legs to support their enormous weight, so their bones were huge and solid. The smaller, fast-running bipedal herbivores like Dryosaurus needed to be fast; thus, they had long, thin-walled bones. These bones were essentially hollow tubes, and the insides were filled with a light bone marrow. This gave them a strong, flexible, but light-weight, structure, enabling them to move swiftly when circumstances demanded it such as running from a predator.

 
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