Echidna!
Sure, everyone's gone "WTF" over the platypus, but what about its even weirder cousin the echidna (also known more descriptively as the spiny anteater)? Together, they are the only surviving examples of the oldest mammals ever to exist, the monotremes. Monotremes have fur, and some of them sometimes have pouches in which their young develop, but they also lay eggs and have bills, sort of like birds, and in the case of male platypuses poisonous ankle spurs also. (If stung by a platypus, you will experience horrible pain for weeks. No drug will help.) The platypus also has ten sex chromosomes for some reason.
The female echidna does not usually have a pouch, but she grows one as necessary. About three weeks after mating she doubles over and lays her single egg right into the temporary pouch. After a while the egg hatches in there, producing the baby echidna, which is called a puggle and looks like a wad of chewing gum. And echidnas are covered with aggressive spines, which makes things more complicated, as the mother cannot carry her puggle once these start to develop. So she buries it. (Echidnas are good diggers; if you startle one it will sink as if by magic into the ground until only its spines are exposed. In this position it is all but unassailable.) Alternately, she hides it under a bush. Every five to ten days she unburies it and lets it nurse for a while before burying it again.
Monotremes are mammalian, even if what they have is a kind of free demo version of mammalianism without the really useful features like live birth, so they lactate. But they have no nipples. The milk just leaks right out of glands in their skin, and the baby monotreme laps it up with sweeps of its tiny bill.
Echidna mating is rarely observed, but the following seem to be the basics. It begins when the female goes into estrus. Males, usually three or four of them, but sometimes as many as eleven, start following her around in a long single-file line called an "echidna train" (or even "echidna love train"). It seems very civilized, though it can go on for as long as six weeks, during which time the otherwise solitary animals eat and sleep in each other's company, and the males nip the female's tail, which seems to be a kind of foreplay. Eventually the female echidna climbs partway up a tree, or buries part of herself in the dirt, leaving the males to walk around and around her until they have created a circular rut in the ground. (Sometimes there's only one male, in which case, nothing daunted, he kind of walks back and forth by himself until he has created a little ditch.) Then they engage in a shoving contest. The males that get shoved out of the ditch acknowledge defeat and leave peacefully until only one, the best shover, is left. He gets to mate with the female -- very carefully, because they are both covered with spines. (Understandably, echidnas do it face to face, so don't listen to anyone who tells you that this is a uniquely human behavior.) The male's four-headed penis, which he does not use to urinate, emerges only during the act of mating; the rest of the time he is indistinguishable from a female echidna, as his testicles are also inside his body.
Four-headed penis. WTF, nature?
The female echidna does not usually have a pouch, but she grows one as necessary. About three weeks after mating she doubles over and lays her single egg right into the temporary pouch. After a while the egg hatches in there, producing the baby echidna, which is called a puggle and looks like a wad of chewing gum. And echidnas are covered with aggressive spines, which makes things more complicated, as the mother cannot carry her puggle once these start to develop. So she buries it. (Echidnas are good diggers; if you startle one it will sink as if by magic into the ground until only its spines are exposed. In this position it is all but unassailable.) Alternately, she hides it under a bush. Every five to ten days she unburies it and lets it nurse for a while before burying it again.
Monotremes are mammalian, even if what they have is a kind of free demo version of mammalianism without the really useful features like live birth, so they lactate. But they have no nipples. The milk just leaks right out of glands in their skin, and the baby monotreme laps it up with sweeps of its tiny bill.
Echidna mating is rarely observed, but the following seem to be the basics. It begins when the female goes into estrus. Males, usually three or four of them, but sometimes as many as eleven, start following her around in a long single-file line called an "echidna train" (or even "echidna love train"). It seems very civilized, though it can go on for as long as six weeks, during which time the otherwise solitary animals eat and sleep in each other's company, and the males nip the female's tail, which seems to be a kind of foreplay. Eventually the female echidna climbs partway up a tree, or buries part of herself in the dirt, leaving the males to walk around and around her until they have created a circular rut in the ground. (Sometimes there's only one male, in which case, nothing daunted, he kind of walks back and forth by himself until he has created a little ditch.) Then they engage in a shoving contest. The males that get shoved out of the ditch acknowledge defeat and leave peacefully until only one, the best shover, is left. He gets to mate with the female -- very carefully, because they are both covered with spines. (Understandably, echidnas do it face to face, so don't listen to anyone who tells you that this is a uniquely human behavior.) The male's four-headed penis, which he does not use to urinate, emerges only during the act of mating; the rest of the time he is indistinguishable from a female echidna, as his testicles are also inside his body.
Four-headed penis. WTF, nature?