The remora’s ridiculousness makes it a fascinating evolutionary puzzle just waiting for the solving. Other species clamp themselves onto other animals–whale barnacles, for example, grow prongs from their shells that anchor them to whale skin–but among fish, remoras are exceptional. Their closest relatives include Mahi-Mahi and amberjacks, neither of which has anything on their head that even faintly resembles the remora’s sucker. Only after the ancestors of remoras and these ordinary fish split apart some 50 million years ago, the remoras evolved a remarkably new piece of anatomy.

When you look closely at the remora’s suction disk, its remarkableness only grows. It looks like a spiked Venetian blind. Pairs of slat-like bones called lamellae form a series of rows running down the length of its head, and muscles running from the remora’s skull to those bones pivot them, creating spaces between the rows.