Remoras, or shark suckers, are a family of eight species of tropical fish that for more than a millennium have inspired a mythology that is almost stranger than those odd little hats they've got on. The hats are sucking disks that remoras use to latch onto pretty much anything for a free ride, whether it is other fishes, turtles, divers or ships.

Now scientists have figured out where the shark sucker's sucking disks actually came from. In a study published in the December 2012 Journal of Morphology, ichthyologists (fish experts) injected red dye into the bones of larval remoras and other fishes so they could watch them grow. Up to a certain point, the dorsal fin and supporting skeleton appeared to develop in the same way in both kinds of fishes. Then the remora's dorsal fin bones expanded and shifted forward toward the fish's head. By the time the juvenile remora had grown to 30 millimeters long, it had a two-millimeter-long, perfectly formed sucking disk.