But, in reality, the supercadioid pattern is NOT a shotgun pattern. by definition, a shotgun mic needs to have an interference tube in front of the capsule. I think it's the marketing people at Audix who are confusing the terms. and it's too bad, because they are suggesting that two distinct microphone types are the same, which they aren't. that's why I suggesting getting in touch with Audix and getting more clarification directly from them.
Jason nailed it. The terms are sometimes used interchangably, but that confuses things. Hypercardioid describes a shape of pickup pattern closer to the figure-8 side of the continuum from figure-8 to omni (typically described as: figure-8, hypercardioid, supercardioid, cardioid, subcardioid, omni). All those patterns can be described mathmatically as a simple mixture of omni an figure-8 components in different ratios. The coloquial term 'shotgun mic' really describes the apperance of the mic as a way of building a highly directional mic than a specific pickup 'pattern'. Although people will know what you mean if you refer to a shotgun pattern, that doesn't fit along that mathmatical continuum. It's sort of like 'boundary mounted omnis'- not a pattern per say, but a technique that has the effect of changing a standard capsule's directionality.
'Shotgun' microphones are often built around supercardioid capsules, but they don't have to be. More importantly, they use a long interference tube in front of the capsule to increase the directionality. The interference tube has slots along it's length arranged so that sounds arriving off-axis through the slots are phase delayed and self-cancel somewhat, where sounds arriving on-axis do not. As I understand it, the longer the interference tube, the more consitant the increased directional pattern is at lower frequencies. The typical apperance of the long tube is where the term 'shotgun' comes from. That distinction is somewhat blurred now that there are some highly directional mics that use complex (and expensive) electronic means to increase directionality, do so more consitantly across the spectrum, and have a somewhat better behaved off-axis response, but they still use an intereference tube even if they are generally shorter than traditional 'guns'. The interference tube cancelation technique doesn't lend itself to smooth off-axis response and that's why it's difficult to make really good sounding guns for recording music.