Looked a lot like an armless anaconda, or a fig-4 guillotine. It was beautifully executed, one of the best I've seen in MMA. According to my lessons that is how the guillotine is supposed to be done, but because the windpipe crush can also work and is easier people do that more often.
EDIT: Bruce - my previous instructor was a guillotine wizard, he taught the guillotine as:
reach deep and across, you want you elbow pit on the trachea, not your forearm blade
your shoulders should be 30-45 degrees off parallel with the choking arm's shoulder as the lower one
you fold the head AND twist while crunching, you NEVER pull away
The most granular details are lost to memory but I remember those points.