You won't believe this.
It happened on May 3, 2012, around 22:30 CEDT.
Just as I was setting up my scope, I accidentally pressed the shutter release of the already attached camera. I hadn't even focused yet. And what did I see? Apparently I had managed to photograph a pteranodon as it was crossing the lunar disc, seen from my vantage point. Wow - not only are they not extinct, but they also appear to be nocturnal. I guess they will have to rewrite all the textbooks on paleontology.
Check it out:
It's over the Mare Imbrium, just West of the Appenine range.
OK, right, so it probably was a bat, not a pteranodon.