Its teeth are designed not so much to grab or slice fish but to prevent them from escaping once the coelacanth has sucked them into its gaping maw. Beneath the chin lie large, bony plates.

A tiny, scaleless, freshwater fish, the highly endangered unarmored threespine stickleback is a fierce protector of its nest, which it defends by dashing forward with gaping mouth and “hackles” raised ...