Help me, I'm drawing a blank. I believe he lost one to Shields and one to Condit (maybe two to Condit on one of the judges scorecards?) The TKO defeat in the 1st round to Serra doesn't technically count as a lost round. Who else has he lost a round(s) to since '04 and how many?
I think it's possible GSP has lost fewer total rounds since '04 against his 18 opponents than A. Silva has against Sonnen alone (lost four in the 1st fight and the first round in the second fight - 5 total). Plus one lost round to Lutter and one to Henderson. Not sure if I've forgotten anyone else.
Anyway, with all the 5 round bouts GSP has had, I'm thinking you can probably still count on one hand the total number of lost rounds he has had. I just can't think of what they are right now. Any help?
On the judges scorecard he may have lost a round to Shields. That also happened with the first round of GSP/Koscheck 1 even though GSP pretty clearly won that round.
He has lost these many rounds according to judges
1-2 vs BJ 1 (split decision
29-28 x2
28-29 x1
Kos 2 possibly lost first rlund not too sure
2 to Shields according to the scorecards of atleast one ref
He did not lose round 3 vs Condit on the scorcards 
/\/\/\ Good catch on the Penn fight. That's the only one I recall him looking like he had any chance of actualy losing (early on, anyway) since his Hughes defeat. He has embarrassed everyone else. I am surprised at least one of the judges had him losing 2 rounds to Shields, and not just 1. I thought I remember him dominating 4 rounds of that fight, but maybe I just forgot.
He certainly lost the first round vs BJ in their first fight 