amargasaurus

A dinosaur with both spines and a fan!

As of this writing (2025), the 'skin sail' hypothesis for Amargasaurus seems to have the most evidence for it; the long spines that trail down its neck and back were most likely covered with and connected by skin, similar to some modern chameleons.

This isn't the only theory that has been offered as to the purpose and appearance of Amargasaurus' distinctive spines, however; another theory, less supported now, is that the spines were unconnected to each other and covered in keratin, the same material that covers animals' horns and hooves.

This pattern includes instructions for stitching both options.