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.