What does the spine do on the spinosaurus?

There is some disagreement over the function of such structures such as the fan-like spinal structure on the Spinosaurus. As similar structures are often found in slower moving dinosaurs such as Stegosaurus, this leads scientists to believe it was a form of conductor, to allow the dinosaur to absorb heat from the sun. It may also have been used to shed body heat. I personally follow the theory that its primary function was to act as a sail or dorsal fin, exactly as you would find on a Sailfish. This would allow for sharp maneuvers and aid turning ability and agility, just as it does for fish today.

It is possible that it is a combination of these things.