Sapient Bananogmius

Bananogmius is a genus of ray-finned fish that lived during the Late Cretaceous period. It was found in what is now Kansas, USA. It had a thin body, similar to that of a modern angelfish, and dozens of small teeth. However, it is best known for the tall dorsal fin on its back, which looked like a sail. It is unknown what this sail would have been used for.