Heavy quark spin symmetry and heavy flavor hadronic molecules

We argue that the heavy quark spin symmetry can lead to important consequences for heavy flavor hadronic molecules. It can be used to predict new heavy flavor hadronic molecules and hence provides a method to identify the nature of some newly observed exotic hadrons. For example, if the Y(4660) were an S-wave Ψ'f0(980) shallow bound state, then the mass, width and line shape of its spin partner are predicted.