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I'd leapt at the title, thinking that the article claimed evidence for a fourth-generation (u,d), (c,s), (t,b), (something new) quark, which would be incredible news. This article describes the potential observation of a four-quark bound system, made up of known quarks in a novel arrangement.

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Although a 4th generation would certainly be a bigger deal, tetraquarks have never been seen and would have important implications for our understanding of QCD.

http://en.wikipedia.org/wiki/Tetraquark

Although a tetraquark particle is possible, the Z(3900) might also be explained by two weakly bound mesons (two-quark particles)--which would be less interesting and more likely, in my humble opinion.

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