Something extremely rare happened on a farm in Vermont the other day. A live, healthy two-headed calf was born. Follow the link to the news report to see video of the calf. The likely cause of the calf having two heads on only one body was a partial split of the embryo in the early stages of development leading to a condition called polycephaly (meaning having more than one head). If the embryo had completely split it would have formed two healthy twin calves. For more on embryo development, check out Seth's post. Unfortunately this one died but I'm curious to see what kind of halter they'll come up with for the one that will inevitably survive sometime in the future.