A newly discovered fish in the Mekong River in Vietnam has a, how shall we say this, unique male anatomy: its penis is on its head.
And the weirdness doesn't stop there:
Male priapiumfish don't have a penis like humans and other mammals. Instead they have a unique organ called a priapium, which faces backwards and looks like a muscular nozzle. It's actually a modification of the fish's pectoral and pelvic fins.
The priapium of P. cuulong has two attachments, both of which look frankly dangerous. At the bottom near the tip, there is a forward-facing serrated saw, or ctenactinium. Further forward, right under the head, there is a forward-facing rod called the toxactinium.
No one has seen P. cuulong mating, but based on observations of other species it's likely that the saw and rod are used for grasping the female during mating. One goes on either side of her head, holding her still while the male transfers his sperm.
Michael Marshall of New Scientists explains: LinkPreviously on Neatorama: 30 Strangest Animal Mating Habits