Dear Sir, I found the attached item on St. Augustine Beach, Florida. Could you tell me what it is. It is about 7 1/2 inches long. Thank You in advance.
Hard to nail it down from just this photo, but my best guess is that you found a dorsal spine of a billfish,(perhaps a sailfish or marlin).
Spines from stingrays generally have serrations on both sides not just one, but I would not rule that out completely either.
The basal attachment area appears highly similar to that of the marlin spine (attached photo).
Best I can do from your pic.