wow
those are the best mammatus clouds i have ever seen. I can see why you would suspect them fake. I live in central texas but i grew up in tornado alley (north texas) and have never seen mammatus as well defined as these before.
mammatus form when there is no jet stream in the top of the storm to 'blow' away the top of the thunderstorm so instead of heat rising up intil it meets the jet stream and is blown away, it rises till it is cooled above the freeze line, then falls slowly until it melts, then rises again, acting in a slow micro scale rotation.
an example of more regularly seen mammatus taken a few weeks ago
http://www.entropiaforum.com/gallery...p?i=26444&c=19