I say opossum, and here is why:
The baby is fully formed but not fully developed. It has no placenta as it would if it were aborted from a mammal like a dog/cat or such. I think it probably fell out of its mother's pouch. Most likely, it had weakened and died before it came out of the pouch, as these little babies usually latch on and do not let go. Very kind of you to bury the little critter.
Hubby just walked in and said his standard answer of "chupacabra".
