Anglerfish have invisible fangs, narwhal tusks are extra-long canines, and more facts from the weird and wonderful study of ...

They had small, rough scales, fixed fins, and sharp, replaceable teeth. The second group, the bony fish, were covered in scales and had maneuverable fins and gas-filled swim bladders for ...

Their skin is covered with denticles, tooth-like scales that differ from the scales of bony fish. And they have five, six, or seven gill slits per side, not one per side as in bony fish.