Since shark skeletons are comprised of cartilage not bone, their parts aren’t that commonly found on the beach. The one exception to that rule is shark teeth, but those are made of dentin, a calcified material which is harder than bone. (Side note: The average shark goes through over 25,000 teeth in a lifetime.)
As you can see in the first photo, the cartilage is added in layers, which creates a tree-ring-like signature that can aid in assessing the shark’s age. Some researchers are even extrapolating environmental information from the isotopes captured in each ring. Nature is so cool!