Name that thing!

So, when we were in Tampa for the cousin's wedding, Craig, Kris, Syd, Mom and me all hit the beach for about an hour or so. Enough time to get wet, get sandy, make a Nemo sandcastle, and for Syd to get sand in her eyes twice and have a hysterical fit both times. That's about par for the course with a 3-year old.

I always like to take home a souvenir from any beach outing — a shell, or a particularly nice rock or sea glass will do. And then this thing washed up.

I've got no idea. At first someone said it was a "whale tooth,"and in some way it does resemble a tooth — albiet with a particularly thin, curvy end. The fat part seems root-like, and it feels like cartilage, firm and flexible at the same time. More brittle now than when it was wet. Now that it's dried, it has a natural sheen.
And as you can see, it's about 7 inches long. Weighs almost nothing. Has just a vague briny scent left. And then someone else speculated it was like that stingray barb that killed Steve Irwin. But I've googled "whale tooth" and "stingray barb" and what comes up doesn't really look like this.

So, any suggestions? Any marine biologists out there who can fill me in? And most importantly, is it worth anything?