Curiouser and curiouser
This is intriguing: apparently (update: some) male beavers have uteri (wombs) (update: to some degree), and apparently this is normal for the species (i.e., not a pathology caused by pollution or other environmental factors).
At least, that's a side discovery of the preliminary result of a search on the embryology of the urogenital system of the beaver. I've got a bad case of work avoidance on my final project for a class, which is why I'm doing the search on beaver embryology in the first place. This is just the kind of fun serendipity that will pull me further away from my paper if I let it. So, reluctantly, I am putting aside beaver cloacae and "persistent male uteri" until after I turn in my paper on Tuesday.
But this does get more and more interesting: beavers seem to be unusual mammals structurally on a couple of different counts. Adaptations to a semi-aquatic lifestyle, perhaps? I'll let you know what I find out--but after Tuesday...