Hi, if you haven't seen this before I imagine it does look odd. Dogs and cats have long narrow uterine horns instead of a large single round uterus like humans. Their placenta grows in a circle around them and is called a zonary placenta. Usually when they are born the placenta will let the puppy slide through and then is pulled out behind the puppy almost inside out. Since your puppy was so tiny it probably didn't have the size to turn the placenta inside out or the placenta may have detached a little early for some reason. Here is a wonderful website (with great pictures) explaining about zonary placentas. :-) Good luck with your little guy.
Placentation in Dogs and Cats
Teresa