SHARKS HAVE CARTILAGE FOR BONES
One reason i have barely any pictures of ancient shark skeletons is because, SHARKS BARELY FOSSILIZE, 10% of most sharks from the cretaceous to now are bones, the rest is cartilage, some old sharks had bones because they were early fish but, eventually fish started being cartilaginous, an example being Helicoprion a shark like cartilaginous fish, closely related to the ghost shark, which is not a shark, and enjoy the picture of the ammonite-like Helicoprion buzzsaw jaw.