How Do We Estimate The Ages Of Dinosaurs?

Recently, Scientist's Have Found That Most dinosaurs had bones with growth rings (Called lines of arrested growth, abbreviated LAG) by which we can calculate the age's of Dinosaurs....These Lines are visible only under a microscope.....

The Bones have to be sliced into thin sections and Viewed with a polarized lens under the microscope. Its Quite similar to looking at the growth rings of trees to determine the ages of a Tree. Each Year of growth leaves a trace in the bone( or tree trunk ). Another method to estimate their ages is based on the size of their bodies, The Known life span of the modern-day animals, and the fact the larger animals, generally live longer than the smaller ones.....

It has been estimated that the huge sauropods like Apatosaurus, Brachiosaurus, Diplodocus and Supersaurus, lived to be Roughly 100 years of age....Smaller Dinosaurs Probably had shorter life-spans....