Paleoart of Helicoprion, a strange holocephalan, a shark-like fish with a bizarre lower jaw. Helicoprion's whorl has gone through a huge variety of interpretations over time. Luckily, more complete fossils indicate that the whorl looked something like, well, a skin-and-flesh covered whorl, to the extent that with mouth closed, the animal's teeth wouldn't even be visible! By biting cephalopods, the motion of this whorl "rocking" back into the mouth, like a pizza cutter, would have shucked them right out of their shells! Presumably, this could have also absolutely obliterated smaller fish as well, cementing it as an aquatic apex predator. In the modern day, many species of sharks and whales are known to spyhop - the action of poking one's head out of the water to investigate what's going on. Helicoprion may have done the same.
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