How do you tell what an animal is by its bones?

The age of the dinosaur bone is scientifically determined by dating the rock strata in which it lies. The sedimentary rock that composes the individual strata are correlated with radiometrically dated samples of igneous and metamorphic rock which have been associated with the sedimentary rock at the time of its deposition or lithification. In other Words, if a volcano happened to be erupting lava on the surface at the same time a dinosaur died and was covered by ash or tephra, then the age of the dinosaur can be determined to be of a very specific age.