Bolboporities uncinatus

Bolboporites uncinatus, a peculiar (more so than usual) eocrinoid from the Ordovician.

Bolporites is an enigmatic genus, known from numerous species of slightly curved, ice-cream cone-shaped fossils. They were originally thought to be some sort of coral, then were thought to be the spines of an oreasterid-like starfish. Now, though, they are thought to be the body+stem of an eocrinoid.