Can I call myself an ultra runner now?

It would be a reaaaaaly skewed oval sticker that says "thirty-seven and some change"

In all seriousness, it will be cool to see how you like it if you end up doing an ultra. Eventually I would like to do one but I will probably wait a few years for sure. 

Normally I'd say 'no', and that you'd have to do it in a sanctioned race/run but... it was like 110 degrees on Sunday.

so, I'll give you a pass on that one.

Your question is pretty timely to me as I just ran my first ultra last Saturday.  I've done 5 marathons and 2 IM's over the past two years so I have some basis for comparison.  In fact, a friend of mine that was there asked me right after the race which was tougher, an IM or a 50 miler.  For me, there was no debate, I felt worse in the later stages and after the IM's.  I think I even felt more intense post-race pain and discomfort from the marathons but there are some differences.

I think the intensity and faster pace generate so much more pounding on the legs during a marathon.  So muscle pain and discomfort were greater with the marathon but energy levels and thus recovery has actually been slower for me with the ultra.  What surprised me is how mentally tired I continue to be.  My physical recovery is taking a little longer.  I usually am swimming or spinning lightly after one day off from a marathon but I'm two days out now I really am going to have to force myself to do anything this evening if at all.

Sounds like you would have no problem with an ultra, given I guess that you just did one but I'd encourage you to participate in an official one.  It was one of the greatest, most rewarding experiences in my life. 

Another year down