Stegosaurus was one of the first famous dinosaurs ever found, with the first decent skeleton dug up in 1877. Almost 150 years later, scientists still can’t agree on what those huge plates running down its back were actually for.
The first guess was armor - until someone realized the plates were thin, hollow, and broke easily. Useless for a defensive shield. Other theories: cooling the body by acting like big living radiators (the plates have lots of blood vessel grooves), warming the body in the sun, or displaying mood and species - possibly flushing with color when Stegosaurus felt threatened or wanted a mate.
The strangest thing? The plates weren’t even attached to the skeleton with bone. They were embedded in the skin, like giant shingles, which is why we sometimes find them lying loose next to a Stegosaurus skeleton instead of in their proper positions.
