OLD EGG-THEMED THREAD REPOST
It took almost a century between the platypus becoming known to western scientists and conclusively proving that they laid eggs. Oh, and there were a few existential crises along the way.
For the first couple of decades of knowing about platypuses, quite a lot of them were convinced it must be a hoax, because look at it.
Platypuses have traits of birds and reptiles, but also have traits of mammals. Rather puzzling to scientists picking over pickled specimens was their internal reproductive system was more like a bird than a mammal.
Female platypuses don't have vaginas. They have a cloaca, which is a single hole for pee, poo, sex and eggs. Eggs. Which they lay.
The female platypus has two ovaries, but only the left one is functional. They also have two organs which can be called uteruses or oviducts. The embryo isn't in there very long, and the uterus puts a shell on it before laying the egg.
The weird inner junk aside, platypuses also don't have nipples, even though they produce milk, like other mammals. They secrete it through the pores in their skin, which then pools on their belly. Their young lap it up from these little milk bowls.
Vagina Museum
Advanced Persistent Teapot