This long, slender, deep-sea eel has remarkable jaws, shaped like a bird’s bill, with the ends turned out so that they can never fully close. When the males mature and are ready to spawn, their jaws shorten, they lose all their teeth, and their front nostrils grow into large tubes. This probably enhances their sense of smell, helping them to find mature females. It has a lifespan of ten years. Its larvae are shaped like leaves, which actually get smaller before transforming into adults.
It has more vertebrae in its backbone than any other animal, around 750. However, its anus has moved forward during its evolution and is now located on its throat.