Every time I think I understand how weird platypuses are, I obtain additional information that further weirdifies them.
Popular Science has a great little piece that kicks off by talking about a new study on platypus milk, which is apparently loaded with a powerful antibiotic that science has found nowhere else in nature. That's pretty cool to begin with – it might be possible to harness that antibiotic, for example, to deal with antibiotic-resistant strains of bacteria!
But PopSci uses this study as a hook to deliver a full-on recitation of platypian oddness, which brought untold joy into my heart:
Really, almost everything about platypuses defies how we think about most mammals.
They do give milk to their babies, but unlike almost all other mammals they don't have nipples. Instead, they essentially sweat out their milk from pores along their stomachs. The platypus has a bill kind of like a duck, but it's really more of a hard snout. Their nostrils are on top of the snout, the mouth on the bottom, and oh yeah, they also sense their prey by detecting electrical fields. They literally close their eyes, ears, and nose when they dive underwater and go mainly on electroreception.
It also has some bonus bones in its shoulder not found in any other mammals, and rather than having its legs mounted beneath the body, its appendages spring out from the sides like a reptile. That means they also don't swim like other mammals, who tend to use all four limbs. Platypuses let their back legs dangle—even though they, too, are webbed—and propel themselves entirely with the front feet, steering with the tail.
They have venom, but not in the teeth. It's found in little spurs on their feet, and seemingly not to kill prey. Venom is for intimidating other platypuses.
Platypus eyes aren't like those found on any other four-legged creature, either. They more closely resemble those of a hagfish or lamprey, because of course they do.
As one of the scientists for that milk-study said in her own press release, "Platypus are such weird animals that it would make sense for them to have weird biochemistry."
(CC-licensed photo via Matt Chan)