While studying some flashcards for the OAT, I came across a question I didn't know. I can't remember how the question was exactly worded, but it went something like:
True or False: Marsupials have placentas.
Pretty straightforward question, but I had no idea whether it's true or false. Well, it turns out that they don't have any placentas. Isn't that weird? They give birth to teenie-weenie marsupial babies after all the nutrients on the egg have been used up. Once born, the teenie-weenie babies have to crawl up to their mommy's pouch, where they stay until they're fully developed. The babies are so tiny when they're born. They're pretty much like helpless embryos. It's a miracle that they even make it.
Check out this amazing video.