Fossil Matter Trivia II: Can you identify this fossil?

In our previous trivia, I posted the image of an ammonite. This was a group of cephalopod mollusks that went extinct in the late Cretaceous along with the dinosaurs. These were marine predators, some of them growing a few meters in diameter.

The specimen from the previous post is a Perisphinctes cubensis from the middle Jurassic black limestones and shales of Pinar del Rio, western Cuba. These fossils can be found on river rocks and rock walls.

But this post will be harder. Can you identify this fossil?