How do scientists figure out how much a dinosaur weighs when they have only bones, and not the skin and muscle?
Alison, 11, South Dakota

Dr. dig responds:
Bones and teeth can be very informative. The size and shape of teeth and jaw suggests the type of diet of the animal‹did it eat meat, vegetation, or both? The size, shape and weight of the bones suggests the strength of the muscles that would have been needed to move the skeleton. This information can be compared with measurements taken from modern, living animals, and can be used to estimate original size and weight. Footprints preserved as fossils, too, help to determine weight. A footprint will tell an expert how an animal walked (on tiptoe? with the whole foot touching the ground? on four legs, or two?), and how much pressure it exerted on the ground.